JP2011096356A - Multilayer hard magnet and read/write head for data storage device, and manufacturing method of hard magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic material with high coercivity and relatively small magnetic grain sizes. <P>SOLUTION: A hard magnet 1600 includes a seed layer 1602 containing a first component including at least one of a platinum group metal, Fe, Mn, Ir and Co, a cap layer 1612 containing the first component and a multilayer laminate 1604 between the seed layer 1602 and the cap layer 1612. The multilayer laminate 1604 includes a first layer 1606 containing the first component and a second component including at least one of the platinum group metal, Fe, Mn, Ir and Co. The second component is different from the first component. The multilayer laminate 1604 further includes a second layer 1608 which is formed on the first layer 1606 and contains the second component and a third layer 1610 which is formed on the second layer 1608 and contains the first component and the second component. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  This application is a continuation-in-part of US Patent Application Serial No. 12 / 112,671, filed April 30, 2008, the entire contents of which are incorporated herein by reference.

BACKGROUND Magnetic data storage includes a magnetic read / write head. It detects and changes the magnetic properties of the magnetic storage medium. For example, the read / write head includes a magnetoresistive sensor that changes resistance according to an applied magnetic field. Based on this resistance change, the read / write head senses or changes the magnetic properties of the magnetic storage medium.

  In one aspect, this disclosure provides a seed layer that includes a first component that includes at least one of a Pt group metal, Fe, Mn, Ir, and Co, a cap layer that includes the first component, and a seed layer and a cap. Directed to a hard magnet, including a multilayer stack between layers. According to this aspect of the disclosure, the multilayer stack includes a first layer that includes a first component and a second component that includes at least one of a Pt group metal, Fe, Mn, Ir, and Co. However, the second component is different from the first component. The multilayer laminate further includes a second layer formed on the first layer and including the second component, and a third layer formed on the second layer and including the first component and the second component. May be included.

  The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. These and various other features and advantages will be apparent from the detailed description below.

1 is a schematic diagram of a hard disk drive. It is a block diagram showing a hard disk read head including a tunnel magnetoresistive sensor. It is a block diagram which shows a hard-disk reading head. It is a block diagram which shows another hard disk read head. FIG. 2 is a phase diagram for a platinum-iron binary system. A Tetsuji crystal unit cell of the original alloy - L1 ₀ phase constitution platinum. It is a block diagram of a multilayer structure including a seed layer, a cap layer, and an intermediate alloy layer. 2 is a plot of magnetic moment versus magnetic field for an iron-platinum magnetic material formed as a single film layer. 2 is a plot of magnetic moment versus magnetic field for an iron-platinum magnetic material formed with a platinum seed layer. 2 is a plot of magnetic moment versus magnetic field for an iron-platinum magnetic material formed with a platinum cap layer. 2 is a plot of magnetic moment versus magnetic field for an iron-platinum magnetic material formed with both a platinum seed layer and a platinum cap layer. FIG. 6 is a plot of magnetic moment versus magnetic field for an iron-platinum alloy formed with a seed layer and cap layer containing one of silver or platinum. FIG. 6 is a plot of magnetic moment versus magnetic field for an iron-platinum alloy formed with a seed layer and cap layer containing one of silver or platinum. FIG. 6 is a plot of magnetic moment versus magnetic field for an iron-platinum alloy formed with a seed layer and cap layer containing one of silver or platinum. FIG. 5 is a plot of magnetic moment versus magnetic field for an iron-platinum alloy formed with a seed layer and cap layer containing one of iron or platinum. FIG. 5 is a plot of magnetic moment versus magnetic field for an iron-platinum alloy formed with a seed layer and cap layer containing one of iron or platinum. FIG. 5 is a plot of magnetic moment versus magnetic field for an iron-platinum alloy formed with a seed layer and cap layer containing one of iron or platinum. FIG. 5 is a plot of magnetic moment versus magnetic field for an iron-platinum alloy formed with a seed layer and cap layer containing one of iron or platinum. 2 is a plot of magnetic moment versus magnetic field for various compositions of iron-platinum alloys formed with a platinum seed and cap layer. 2 is a plot of magnetic moment versus magnetic field for various compositions of iron-platinum alloys formed with a platinum seed and cap layer. 2 is a plot of magnetic moment versus magnetic field for various compositions of iron-platinum alloys formed with a platinum seed and cap layer. It is a transmission electron microscope (TEM) micrograph of the iron-platinum magnetic material provided with the platinum seed layer and the platinum cap layer before annealing. It is a transmission electron microscope (TEM) micrograph of the iron-platinum magnetic material provided with the platinum seed layer and platinum cap layer after annealing. FIG. 6 is a plot of concentration versus depth for an iron-platinum magnetic material with a platinum seed layer and a platinum cap layer prior to annealing. FIG. 4 is a plot of concentration versus depth for an iron-platinum magnetic material with a platinum seed layer and a platinum cap layer after annealing. 2 is a plot of magnetic moment versus magnetic field for an iron-platinum magnetic material formed with a platinum seed layer and a platinum cap layer. 1 is a block diagram of a multilayer iron-platinum alloy including two layers with different compositions. FIG. 1 is a cross-sectional view for an exemplary multilayer hard magnet. 2 is a composition plot for an exemplary multilayer hard magnet. 1 is a cross-sectional view for an exemplary multilayer hard magnet. 2 is a composition plot for an exemplary multilayer hard magnet. 1 is a cross-sectional view for an exemplary multilayer hard magnet. 2 is a composition plot for an exemplary multilayer hard magnet. 2 is a cross-sectional view of an exemplary read sensor. FIG. 1 is a cross-sectional view for an exemplary multilayer hard magnet. 2 is a composition plot for an exemplary multilayer hard magnet. 2 is a flow diagram illustrating an exemplary method of forming a multilayer hard magnet. 2 is a plot of magnetic moment versus magnetic field for an iron-platinum hard magnet.

DETAILED DESCRIPTION This disclosure is generally directed to magnetic materials used in data storage applications. In some embodiments, the magnetic material may be used in a read / write head for a magnetic data storage device. The magnetic material may be formed from an alloy containing platinum (Pt) and iron (Fe), for example, by low temperature annealing of the alloy, seed layer and cap layer. Magnetic material, preferably, contain an L1 ₀ phase structure, having a high coercive force and a large saturation magnetization as desired.

  In some embodiments, the magnetic material may be formed as a multilayer hard magnet. For example, a multilayer hard magnet may include a seed layer, a cap layer, and a multilayer stack between the seed layer and the cap layer. The multilayer stack may include at least two layers, and the layers may include different compositions. For example, a multilayer stack may include multiple layers that result in a compositional gradient, which are symmetrical about a plane that is approximately equidistant from and substantially parallel to the seed and cap layers. It may also be asymmetric. In some embodiments, the multilayer stack may provide magnets having different magnetic moments in different portions.

  Although this disclosure discusses the use of a magnetic material as a bias magnet in a read / write head for a disk drive, the magnetic material is a magnetic material with high coercivity and a relatively small magnetic grain size. It may be useful in application examples. For example, the magnetic materials described herein may be useful for magnetic media.

  FIG. 1 illustrates an exemplary magnetic disk drive 100 that includes a read / write head according to one aspect of this disclosure. The disk drive 100 includes a base 102 and a top cover 104 shown partially cut away. Base 102 is combined with top cover 104 to form housing 106 of disk drive 100. The disk drive 100 further includes one or more rotatable magnetic data disks 108. Data disk 108 is mounted on spindle 114, which operates to rotate disk 108 about a central axis. Magnetic recording and reading head 112 is adjacent to data disk 108. The actuator arm 110 carries a magnetic recording and reading head 112 for communication with each data disk 108.

  The data disk 108 stores information on the magnetic film as magnetically oriented bits. The magnetic read / write head 112 includes a recording (write) head that generates a magnetic field sufficient to magnetize discrete areas of the magnetic film on the data disk 108. Each of these discrete areas of the magnetic film represents a bit of data with one magnetization orientation corresponding to “0” and a substantially opposite magnetization orientation corresponding to “1”. The magnetic recording and reading head 112 further includes a reading head that can detect the magnetic field of discrete magnetic domains of the magnetic film.

  FIG. 2 is a schematic block diagram illustrating an embodiment of a hard disk read head 200 that may be used with the magnetic read / write head 112 in FIG. The read head 200 reads data from a data disk such as the data disk 108 of FIG. 1 using magnetic resistance. Although the exact nature of read head 200 may vary widely, one tunnel magnetoresistive read head is described as one example of read head 200 in which the disclosed magnetic materials may be utilized. However, it is understood that the magnetic materials described herein may be used in any read head 200 such as, for example, current film surface perpendicular giant magnetoresistive heads, giant magnetoresistive heads, and the like. Furthermore, magnetic materials may find use in many other applications where high coercivity and / or large saturation magnetization is desired.

  1 to 2 again, the read head 200 flies over the surface of the data disk 108 on the air bearing formed by the rotation of the data disk 108. The data disk 108 has a plurality of data tracks 228, one of which is shown in FIG. Data track 228 may be divided into a plurality of bits. As the disk 108 rotates as indicated by the arrows, the read head 200 may follow the data track 228 and read each bit of the data track 228 as the data track 228 passes under the sensor 218.

  The read head 200 includes a first shield layer 202 and a second shield layer 203, a tunnel magnetoresistive sensor 218, and two hard magnets 204 and 205. The first and second shield layers 202 and 203 reduce or substantially block extraneous magnetic fields such as those from adjacent bits on the data disk 108 so as not to affect the sensor 218, Thereby, the performance of the sensor 218 is improved. Ideally, the first and second shield layers 202 and 203 allow the magnetic field from only the bits directly below the sensor 218 to affect the sensor 218 and thus be read. Thus, as the physical size of the bits continues to decrease, the shield-to-shield spacing may continue to decrease.

  The sensor 218 includes a plurality of layers including an antiferromagnetic seed layer 214, a pinned layer 212, a reference layer 211, a tunnel barrier layer 210, a free layer 208 and a cap layer 206. The antiferromagnetic layer 214 is electrically coupled to the first electrode 221, and the cap layer 206 is electrically coupled to the second electrode 220. The pinned layer 212 is formed on the antiferromagnetic layer 214 and exchange coupled to the antiferromagnetic layer 214. Exchange coupling fixes the magnetic moment of the pinned layer 212 with a known orientation. Similarly, the magnetic moment of the pinned layer 212 causes a substantially antiparallel magnetic field in the reference layer 211. Together, the pinned layer 212 and the reference layer 211 form a synthetic antiferromagnetic material 213. The magnetic moment of each of the pinned layer 212 and the reference layer 211 is not allowed to rotate under a magnetic field of interest (eg, a magnetic field generated by a bit of data stored on the data disk 108). The magnetic moments of the reference layer 211 and the pinned layer 212 are perpendicular to the plane of FIG. 2 and antiparallel to each other, as indicated by the arrow tail 224 and arrow head 225 (eg, entering and exiting the plane of FIG. 2). , Generally oriented.

  Sensor 218 further includes a free layer 208, which is not exchange coupled to the antiferromagnet. Therefore, the magnetic moment of the free layer 208 rotates freely under the influence of the applied magnetic field in the target range.

  Read head 200 further includes a pair of bias magnets 204 and 205 that bias the free layer 208 with a magnetic moment oriented parallel to the plane of the figure and generally horizontally, as indicated by arrow 226. To generate a magnetic field. This bias prevents the magnetic moment of the free layer 208 from drifting due to thermal energy that may introduce noise into the data sensed by the read head 200, for example. However, the bias is small enough that the magnetic moment of the free layer 208 can vary depending on the applied magnetic field, such as the magnetic field of the data bits stored on the data disk 108. Sensor 218 and electrodes 220 and 221 are separated from and electrically isolated from bias magnets 204 and 205 by insulators 222 and 223, respectively.

  The tunnel barrier layer 210 separates the free layer 208 and the reference layer 211. The tunnel barrier layer 210 is thin enough that quantum mechanical electron tunneling occurs between the reference layer 211 and the free layer 208. The electron tunneling effect depends on the electron spin and makes the magnetic response of the sensor 218 a function of the relative orientation and spin polarization of the reference layer 211 and the free layer 208. When the magnetic moments of the reference layer 211 and the free layer 208 are parallel, the highest probability of the electron tunnel effect occurs, and when the magnetic moments of the reference layer 211 and the free layer 208 are antiparallel, the lowest probability of the electron tunnel effect occurs. . Therefore, the electrical resistance of the sensor 218 changes according to the applied magnetic field. The data bits on the disk 108 are magnetized in a direction perpendicular to the plane of FIG. 2, into or out of the plane of the figure. Thus, as the sensor 218 passes over the data bit, the magnetic moment of the free layer 208 exits in or out of the plane of FIG. 2, depending on the magnetic field produced by the bit passing under the sensor 218. And the electric resistance of the sensor 218 is changed. The value of the bit sensed by the sensor 218 (eg, either 1 or 0) may therefore be determined based on the current flowing from the first electrode 221 to the second electrode 220.

  In order to increase the storage capacity of a magnetic data storage device such as a disk drive, the size of the magnetically oriented areas (bits) on the data disk 108 is continuously increased to produce a higher data density, It is being made smaller. Thus, the size of the read head 200 may be continually reduced, and in particular, the shield-to-shield spacing may be reduced, and the sensor 218 is substantially free from the magnetic field of adjacent bits on the data disk 108. Isolated. 3 and 4 illustrate exemplary problems that may arise when the shield-to-shield spacing is reduced.

  FIG. 3 shows an embodiment of a read head 300 that includes a first shield 302 and a second shield 303 separated by a distance 301. Similar to the read head 200, the read head 300 includes a sensor 318, a first bias magnet 304, and a second bias magnet 305. The layers of sensor 318 are not shown in FIG. 3 for clarity. First bias magnet 304 includes a plurality of magnetic domains 322, each with a magnetization direction represented by arrow 324. First bias magnet 304 generates a magnetic field represented by magnetic flux lines 320a and 320b (collectively “flux lines 320”). As shown, some of the magnetic flux lines 320b are not released in the face of the magnets 304, 305 and the sensor 318, but instead intersect one of the shield 302 or the shield 303. These flux lines represent the amount of magnetic field generated by the first bias magnet 304 that does not contribute to biasing the free layer of the sensor 318. However, the magnetic flux lines 320a travel through the sensor 318. At least some of this portion of the magnetic field contributes to biasing the free layer of sensor 318 in the horizontal direction (ie, parallel to magnetic flux line 320a).

  FIG. 4 shows a read head 400 that includes a smaller shield-to-shield spacing 401 that may then be used to read smaller magnetic domains on the data disk 108. In the embodiment shown in FIG. 4, the size of the bias magnets 404 and 405 is shown smaller as compared to that in FIG. However, this may not be the case in all embodiments. For example, in some embodiments, bias magnets 404, 405 and sensor 418 may remain the same size, while only the thickness of insulation 428 may be made smaller.

  Regardless of whether the size of the bias magnets 404, 405 and sensor 418 is smaller, the reduction in shield-to-shield spacing 401 results in the magnetic field generated by bias magnet 404 as represented by magnetic flux line 420b. The larger portion goes to one of the first shield 402 or the second shield 403. Available for biasing the free layer (not shown in FIG. 4) as represented by a single flux line 420a as a result of the increased portion of the magnetic field directed to one of shields 402 and 403 The portion of the strong magnetic field is reduced. Because of this lower bias, the signal to noise ratio of sensor 418 may be lower than the signal to noise ratio of sensor 318, which is disadvantageous.

  3-4 illustrate another problem that may occur with a smaller read head 400. FIG. For example, the bias magnet 404 includes a smaller magnetic grain 422 relative to the magnetic grain 322 of the bias magnet 304. The smaller magnetic grains 422 result in a higher probability that the thermal energy present in the system will reorient itself to the magnetic moments of the individual grains 422, as indicated by arrows 426. The reorientation of the magnetic moments of the individual magnetic grains 422 may reduce the overall magnetic moment of the bias magnet 404 and may actually reduce the magnetic moment significantly over time.

  Therefore, bias magnets 404 and 405 with higher saturation magnetization and coercivity are desired. A higher magnetization will increase the magnetic flux of the bias magnets 404 and 405, which helps to bias the free layer, and a higher coercivity will increase the stability of the magnetization. This in turn will facilitate the use of smaller sensors (eg, sensor 418) in the read head 400 of a hard disk drive (eg, disk drive 100).

  Alloys containing iron and platinum group metals will provide a relatively high coercivity and magnetic moment. The Pt group metal may be selected from, for example, Pt, Pd, Ir, Rh and Ru, or combinations thereof. Pt group metals including Pt are preferred, and Pt is particularly preferred.

The alloy may further contain other elements in low proportions, such as (for example) copper, gold, silver and the like. However, in order to provide high coercivity and high magnetic moment, an iron - platinum alloy should preferably contain a high anisotropy L1 ₀ or face-centered tetragonal (FCT) phase structure.

For example, as shown in the iron-platinum (FePt) binary phase diagram of FIG. 5, the L1 ₀ phase configuration has an atomic percentage (at.%) Of about 35 and about 57 at. % Solid solution containing platinum (Pt) and residual Fe and incidental impurities (eg, less than about 1 at.% Impurities). More preferably, FIG. 6 shows a sheet in which Pt atoms 602 and Fe atoms 604 alternate in a 1: 1 atomic ratio (for an alloy with about 50 at.% Pt and about 50 at.% Fe and no accompanying impurities). Shows the _L10 phase configuration that is ordered.

The L1 ₀ phase undergoes a relatively high temperature (above about 500 ° C.) annealing of the FCC disordered alloy (also referred to as an A1 phase alloy) to produce an ordered structure of Pt and iron (Fe) atoms in the L1 ₀ phase configuration. Typically required. This high temperature annealing step prevents the use of FePt alloys in hard disk read heads such as read head 200. This is because the remaining components (e.g., sensor 218) of read head 200 degrade at such temperatures.

  In one aspect, this disclosure is directed to a method of forming an alloy having an ordered phase configuration without requiring a high temperature annealing step. This method generally involves the use of a multilayer structure comprising a seed layer and a cap layer. The multilayer structure further includes at least one intermediate layer comprising an alloy. In some embodiments, the seed layer and / or cap layer includes an alloy component, and in some preferred embodiments, the seed layer and / or cap layer component is a minor component of the alloy.

  FIG. 7 shows a multilayer structure 700 that may be used to produce ordered phase constituent alloys with high anisotropy. The multilayer structure 700 includes a seed layer 702, a cap layer 704, and an intermediate alloy layer 706 formed between the seed layer 702 and the cap layer 704. Alloy layer 706, seed layer 702 and cap layer 704 are formed from a wide range of components including, for example, Pt, Fe, Mn, Ir, Co, etc. for the production of ferromagnetic, ferrimagnetic or antiferromagnetic alloys. May be. In some embodiments, seed layer 702 and cap layer 704 include components present in alloy layer 706. In other examples, seed layer 702 and cap layer 704 include components that are not present in alloy layer 706.

  In some embodiments, at least one of seed layer 702 and cap layer 704 includes two or more components present in alloy layer 706. For example, the seed layer 702, the cap layer 704, and the alloy layer 706 may each include a first component and a second component. In some embodiments, at least one of the seed layer 702 and the cap layer 704 includes a high proportion of components present in the alloy layer 706 in a low proportion. For example, at least one of the seed layer 702 and the cap layer 704 may include a high proportion of Pt and a low proportion of Fe, and the alloy layer 706 includes a high proportion of Fe and a low proportion of Pt. In some embodiments, both seed layer 702 and cap layer 704 include a high proportion of components present in a low proportion in alloy layer 706.

  Seed layer 702, alloy layer 706 and cap layer 704 may be deposited using a number of techniques including, for example, sputtering, ion beam evaporation, chemical vapor deposition, physical vapor deposition, molecular beam epitaxy, laser ablation, and the like. . In one example, seed layer 702 is deposited on the substrate using one of these techniques, and alloy layer 706 is deposited on seed layer 702 using the same or different techniques. And the cap layer 704 is deposited on the alloy layer 706 using any of those techniques.

  Utilization of seed layer 702 and cap layer 704 may be advantageous compared to annealing a single film alloy, annealing an alloy with only seed layer 702, or annealing an alloy with only cap layer 704. . Figures 8A-8D illustrate one such advantage. One important parameter shown in these plots is the coercivity of the alloy. The coercive force is a magnetic field having a magnetic moment equal to zero or a point where a magnetic moment-magnetic field curve intersects the magnetic field axis (x-axis). In-plane coercivity indicates the degree to which atoms are ordered into a regular phase configuration and the degree of magnetic anisotropy in the alloy. That is, a higher in-plane coercivity indicates a more ordered alloy with greater magnetic anisotropy.

  For example, FIG. 8A shows the magnetic moment of the FePt alloy as a function of the applied magnetic field. The FePt alloy of FIG. 8A is about 38 at. % Pt and about 62 at. Annealed at about 300 ° C. for about 4 hours with% Fe. As can be seen, the in-plane coercivity calculated by averaging the absolute values of the coercivity of curves 801 and 802 is about 1420 Oe. FIG. 8B shows an FePt alloy of the same composition as the alloy of FIG. 8A, then formed with a Pt seed layer 702. The sample in FIG. 8B was annealed at a temperature of about 300 ° C. for about 4 hours, similar to the sample of FIG. 8A. The sample of FIG. 8B shows an in-plane coercivity of about 2400 Oe, calculated by averaging the absolute values of the coercivity of curves 803 and 804.

  FIG. 8C again shows that approximately 38 at. % Pt and about 62 at. Results from FePt alloy samples containing% Fe are shown. The sample was annealed with a Pt cap layer 704 at a temperature of about 300 ° C. for about 4 hours. The sample is calculated by averaging the absolute values of the coercivity of curves 805 and 806 and exhibits an in-plane coercivity at about 2200 Oe, similar to the alloy of FIG. 8B.

FIG. 8D then shows that approximately 38 at. % Pt and about 62 at. FIG. 4 shows the results from a FePt alloy sample containing% Fe, formed with a Pt seed layer 702 and a Pt cap layer 704, and annealed at a temperature of about 300 ° C. for about 4 hours. The sample is calculated by averaging the absolute values of the coercivity of curves 807 and 808 and exhibits an in-plane coercivity of about 5100 Oe, which is significantly higher than any of the samples shown in FIGS. 8A-8C. . While not wishing to be bound by any theory, currently available data indicate that this effect is due to interdiffusion occurring at both the seed layer 702 / alloy layer 706 interface and the cap layer 704 / alloy layer 706 interface. Which promotes the ordering of Fe and Pt atoms into the L1 ₀ phase configuration.

  In some embodiments, seed layer 702 and cap layer 704 may include components that are not in intermediate alloy layer 706. For example, in one embodiment, seed layer 702 and / or cap layer 704 include silver, while alloy layer 706 includes a FePt alloy.

  9A-9C are plots of magnetic moment versus magnetic field for three FePt alloys formed with different seed layer 702 and cap layer 704 compositions. As shown in FIG. 9A, before annealing, about 38 at. % Pt and about 62 at. An FePt alloy containing% Fe and having a silver seed layer 702 and a silver cap layer 704 is annealed at about 300 ° C. for about 4 hours to produce a FePt alloy with a relatively low in-plane coercivity of about 200 Oe. To do. FIG. 9B shows the response of an FePt alloy of the same composition as FIG. 9A formed with a silver seed layer 702 and a platinum cap layer 704 after annealing under the same conditions. The in-plane coercivity is much higher, about 1300 Oe. FIG. 9C shows the response of a FePt alloy of the same composition as FIG. 9A formed with platinum seed layer 702 and silver cap layer 704, after being annealed under the same conditions. The in-plane coercivity of this sample is about 2300 Oe. These coercive forces are much lower than the coercivity of the sample shown in FIG. 8D formed with the Pt seed layer 702 and the Pt cap layer 704.

The seed layer 702 and the cap layer 704 are further components that are present in a low proportion (ie, less than 50 at.%) In the intermediate alloy layer 706 or components that are present in a high proportion (ie, greater than 50 at.%) In the intermediate alloy layer 706. Either of these may be included. Utilizing a seed layer 702 and a cap layer 704 that include components present in a low proportion in the intermediate alloy layer 706 may be advantageous in some embodiments. For example, a Pt seed layer 702 and a Pt cap layer 704 may be used to produce an L1 ₀ FePt alloy containing a high proportion of Fe. As another example, a Fe seed layer 702 and a Fe cap layer 704 may be used to produce an L1 ₀ FePt alloy containing a high proportion of Pt.

As a result of utilizing the seed layer 702 and cap layer 704 that contain components present in a low proportion in the intermediate alloy layer 706, the components of the seed layer 702 and cap layer 704 diffuse into the alloy layer 706, while the other component (alloy) The components present in the layer 706 in a high ratio) diffuse from the alloy layer 706 to the seed layer 702 and the cap layer 704. This two component diffusion results in an alloy with a composition closer to the 50:50 ratio of the starting alloy. 2-component spreading further to promote re-ordering of the atoms which are required to produce the phase transition to the L1 ₀ phase.

10A to 10D show that about 36 at. % Fe and about 64 at. A series of samples containing% Pt is shown after annealing at a temperature of about 300 ° C. for about 4 hours. FIG. 10A shows a plot of magnetic moment versus magnetic field for a sample formed with a Pt seed layer 702 and a Pt cap layer 704. The sample exhibits a low in-plane coercivity, poor atomic ordering and low anisotropy. FIG. 10B shows the response of a similar alloy formed with the Pt seed layer 702 and the Fe cap layer 704. The in-plane coercivity is larger, about 700 Oe, which provides better ordering of the Fe and Pt atoms into the L1 ₀ phase configuration than for the sample formed with the Pt seed layer 702 and the cap layer 704. Show. FIG. 10C is a plot of the response of another similar alloy formed with the Fe seed layer 702 and the Pt cap layer 704. The in-plane coercivity is about 600 Oe, similar to that of the sample shown in FIG. 10B.

FIG. 10D shows the response of the alloy formed with Fe seed layer 702 and Fe cap layer 704. Plane coercivity is substantially higher, about 1500 Oe, indicating a better ordering and higher high anisotropy to the L1 ₀ phase structure of Fe and Pt atoms of the alloy layer 706.

  The results shown in FIGS. 9A-9C and 10A-10D show that the composition of seed layer 702 and cap layer 704 plays an important role in forming the ordered phase configuration of alloy layer 706, which is This is indicated by a coercivity of 706. For example, FIGS. 9A-9C show that the annealing process more effectively produces a regular phase configuration having high anisotropy in the alloy layer 706 when the seed layer 702 and the cap layer 704 include components of the alloy layer 706. To suggest. 10A-10D show that the annealing process is then even more effective in forming ordered phase configurations with high anisotropy when the seed layer 702 and cap layer 704 contain components present in a low proportion in the alloy layer 706. Indicates that

The use of seed layer 702 and cap layer 704 is intended to facilitate the formation of ordered phase structures having high anisotropy. Although not wishing to be bound by any theory, the seed layer 702 and the cap layer 704 are alloy components and the interface of the seed layer 702 and the cap layer 704 component of the seed layer 702 and the intermediate alloy layer 706, And may enhance interdiffusion at the interface of the cap layer 704 and the alloy layer 706. This improved interdiffusion of components at this interface may improve the overall ordering of the alloy layer 706 and may further direct the composition of the alloy layer 706 to a more stoichiometric component ratio. This results in alloys containing ordered phase configurations with high anisotropy such as L1 ₀ phase configuration, L1 ₂ phase configuration, and the like.

Due to the enhanced interdiffusion provided by the use of seed layer 702 and cap layer 704, a high coercivity alloy can be formed at a much lower annealing temperature. For example, FePtL1 ₀ alloy may be produced by annealing a multi-layered structure 700 at a temperature in the range of about 250 ° C. within about 6 hours to about 400 ° C.. Preferably, the multilayer structure 700 may be annealed at a temperature from about 250 ° C. to about 350 ° C., more preferably at about 300 ° C. In some embodiments, the annealing may preferably be about 4 hours.

  Lower temperature annealing may limit grain growth in the alloy as compared to higher temperature annealing. This may be particularly desirable, for example, for magnetic materials that are to be used in magnetic storage media. This is because the data density is related to the grain size of the magnetic material.

The amount of alloy ordering and anisotropy, and thus the coercivity, caused by low temperature annealing also depends on the relative amounts of Fe and Pt in the alloy layer 706. FIGS. 11A-11C are plots of magnetic moment versus magnetic field after annealing with a Pt seed layer 702 and cap layer 704 at about 300 ° C. for about 4 hours for three alloy compositions. For example, FIG. 11A shows that about 62 at. % Fe and about 38 at. The response of an alloy containing% Pt is shown. As shown in FIG. 8D, the in-plane coercivity calculated by averaging the absolute values of the coercivity of the curves 1101 and 1102 was found to be about 5100 Oe. FIG. 11B shows that about 70 at. % Fe and about 30 at. The response of an alloy containing% Pt is shown. The in-plane coercivity, calculated by averaging the absolute values of the coercivity of curves 1103 and 1104, was found to be about 4000 Oe. Finally, FIG. 11C shows that approximately 77 at. % Fe and about 23 at. The response of an alloy containing% Pt is shown. The in-plane coercivity, calculated by averaging the absolute values of the coercivity of curves 1105 and 1106, was found to be about 1200 Oe. These results indicate that the Fe content increases and the coercivity of the FePt alloy decreases. What While not wishing to be bound by theory, decreased coercivity is believed to be due to reduction in the ordering of the L1 ₀ phase structure of FePt alloy.

  12A and 12B show transmission electron microscope (TEM) micrographs of the Pt—FePt—Pt multilayer structure before and after annealing, respectively. The darker bands at the bottom and top of FIG. 12A are the Pt seed layer 1202a and cap layer 1204a, respectively, while the brighter intermediate layer 1206a is FePt alloy. After annealing at about 300 ° C. for about 4 hours, the transition from the Pt layers 1202b, 1204b to the intermediate layer 1206b is less obvious, and the layer 1206b itself is a more uniform shadow and has a more uniform phase structure. Implies formation.

13A and 13B show an exemplary plot of composition versus depth for a sample similar to the sample shown in FIGS. 12A and 12B. FIG. 13A shows a pure Pt layer 1302a, 1304a at the surface and a depth of about 200-250 inches. The intermediate region 1306a is about 50 to about 200 inches and has a width of about 60 at. % Fe and about 40 at. Including alloys containing% Pt. After annealing at a temperature of about 300 ° C. for about 4 hours, the sample was measured again, resulting in the plot shown in FIG. 13B. As can be seen, Pt diffused from both pure Pt layers into the FePt alloy. Therefore, the Pt content of layers 1302b and 1304b is about 95 at. %, The Pt content in the intermediate region 1306b of the FePt alloy is about 45 at. It rose to%. Furthermore, although not shown, the phase structure has changed from FCC to L1 _0.

  FIG. 14 shows about 64 at. % Fe and about 36 at. 2 shows a plot of the magnetic response of a FePt binary alloy containing% Pt. The sample was annealed at a temperature of about 300 ° C. for about 4 hours prior to measuring the magnetic response and formed with a Pt seed layer and a Pt cap layer. The alloy exhibits an in-plane coercivity of about 9130 Oe.

FePt alloy with an L1 ₀ phase structure formed by the above method, may form a desired bias magnet for a hard disk read head. The L1 ₀ FePt alloy preferably has a high coercivity and magnetic moment to bias the free layer with the desired magnetization orientation. Furthermore, the relative amounts of Fe and Pt in the alloy may be designed to give the bias magnet the desired properties. For example, the formation of alloys with higher Fe content leads to higher saturation magnetization but lower coercivity. Conversely, the formation of an alloy with a higher Pt content leads to a lower saturation magnetization but a higher coercivity.

  The bias magnet is approximately 80 at. % Fe and about 20 at. % Pt to about 30 at. % Fe and about 70 at. % Pt, preferably about 65 at. % Fe and about 35 at. % Pt to about 40 at. % Fe and about 60 at. % Pt may also be included.

  The FePt bias magnet may have a thickness that depends at least in part on the shape of the hard disk read head. For example, current hard disk read head shield-to-shield distances may range from about 150 mm to about 700 mm. Accordingly, the thickness of the multilayer structure 700 may be up to about 700 mm. In some preferred embodiments, seed layer 702 and cap layer 704 each include a thickness in the range of up to about 200 mm, more preferably from about 25 mm to about 125 mm. The intermediate alloy layer 706 may include a thickness of up to about 400 mm, preferably about 100 to 300 mm.

Bias magnet is formed in the read head as a step in the manufacturing of the readhead (e.g. read head 200), the entire read head, then, may be exposed to a low temperature anneal required to form a L1 ₀ phase constitution. The annealing temperature is sufficiently low so as not to affect the performance of the rest of the read head (eg, sensor 218).

The L1 ₀ phase constituent FePt alloy of this indication may further contain the multilayer of a different composition. For example, the alloy may include a Pt rich layer and an Fe rich layer. Including multiple layers of different compositions will allow further adjustment of the magnetic field generated by the bias magnet, and thus the bias applied to the free and other layers of the sensor.

For example, in many embodiments it may be desirable to have a relatively high bias on the free layer, with a minimum bias on the reference and pinned layers. To accomplish this, as shown in FIG. 15, the bias magnet includes a Fe-rich layer 1506 substantially adjacent to the free layer 1512 and a Fe-rich layer 1504, the tunnel barrier layer 1514. , May be included substantially adjacent to reference layer 1516 and / or pinned layer 1518. Fe rich layer 1506 creates a sufficiently large magnetic field represented by magnetic flux lines 1508 to bias free layer 1512, while less Fe rich layer 1504 possesses a high coercivity, It produces a relatively weaker magnetic field represented by the magnetic flux lines 1510 and therefore does not affect the reference layer 1516 and the pinned layer 1518 equally strongly. Bias magnet 1500 further includes a Pt seed layer 1502 and a Pt cap layer 1520, which are L1 ₀ phase configurations in Fe less rich layer 1504 and Fe rich layer 1506, as described above. Enables the formation of

Furthermore, the method of producing ordered phase constituent alloys may be extended to alloys of other materials. For example, a method of using the seed layer and the cap layer may be used to produce an L1 ₀ phase CoPt alloy for use in applications requiring high anisotropic magnetic material. In addition, this method may be used to produce L1 ₂ phase configured IrMn ₃ or PtMn ₃ materials for use as antiferromagnetic materials.

As described above, in some embodiments, the bias magnet may include multiple layers (multilayer stack) between the seed layer and the cap layer. The multilayer stack may provide the bias magnet with one or more characteristics. For example, in some embodiments, a bias magnet, including a seed layer, a cap layer, and a multilayer stack between the seed layer and the cap layer, is annealed at a reduced temperature to provide a regular phase, eg, L1 _0. It may cause a phase transition to the phase. In such an embodiment, the composition of the individual layers may be different, and the difference in composition between adjacent layers results in diffusion of one or more components of one layer to the adjacent layer and vice versa. Also good. Such diffusion will facilitate the formation of the ordered phase and will lower the annealing temperature that may be used to produce the ordered phase compared to a bias magnet that includes a single intermediate alloy layer. For example, in some embodiments, the bias magnet, formed from a seed layer, a cap layer, and a multilayer stack between the seed layer and the cap layer, has a regular phase at a temperature from about 200 ° C. to about 500 ° C. May be annealed to form. In other examples, the bias magnet may be annealed to form the ordered phase at a temperature of about 200 ° C. to about 300 ° C., or a temperature of about 280 ° C. In some examples, the layers may include alternating compositions, eg, alternating Pt-rich layers and Fe-rich layers.

  In other examples, the layers of the multi-layer stack may have a composition resulting in a bias magnet having a composition gradient, ie, a composition that varies along one or more directions. A bias magnet, including a seed layer, a cap layer, and a multilayer stack between the seed layer and the cap layer, may provide a magnetic moment and / or coercivity that varies in at least one direction of the bias magnet. The magnetic moment and / or coercivity may depend on the composition of the bias magnet. Thus, a bias magnet having a composition that varies along one or more directions may result in a bias magnet having a magnetic moment and / or coercivity that varies along one or more directions. . For example, a bias magnet having a composition gradient from Pt-rich to Fe-rich may have a magnetic moment gradient, a coercivity gradient, or both.

  FIG. 16A shows an exemplary bias magnet 1600 that may include a seed layer 1602, a cap layer 1612, and a multilayer stack 1604 between the seed layer 1602 and the cap layer 1612. In the example shown in FIGS. 16A and 16B, the multilayer stack 1604 includes a first layer 1606, a second layer 1608 and a third layer 1610. In other examples, the multi-layer stack 1604 may include more or fewer layers.

  In general, seed layer 1602 and cap layer 1612 may include at least one component as described above. For example, the seed layer 1602 and / or the cap layer 1612 may include at least one of a Pt group metal, Fe, Mn, Ir, Co, and the like. The Pt group metal may contain at least one of Pt, Pd, Ir, Rh, and Ru. In some embodiments, at least one of the seed layer 1602 and the cap layer 1612 may include at least two alloys of Fe, Mn, Ir, Co, Pt group metals, and the like. Seed layer 1602 and cap layer 1612 may include the same components, or seed layer 1602 and cap layer 1612 may include different components.

  Similarly, the first layer 1606, the second layer 1608, and the third layer 1610 may each include at least one of a Pt group metal, Fe, Mn, Ir, Co, and the like. In some embodiments, at least one of the first layer 1606, the second layer 1608, and the third layer 1610 may include an alloy of at least two components. Each of the first layer 1606, the second layer 1608, and the third layer 1610 may include the same component, the same component alloy, a different component, or a different component alloy. In some embodiments, the first layer 1606, the second layer 1608, and the third layer 1610 include similar components, and the first layer 1606, the second layer 1608, and the third layer 1610 At least one includes a different composition (eg, different proportions of the same component) from at least one other of the first layer 1606, the second layer 1608, and the third layer 1610.

  FIG. 16B is a plot of the composition of one example of a bias magnet 1600, 100 at. % Pt composition to 100 at. Extends to the composition of% Fe. FIG. 16B shows an exemplary composition of the bias magnet 1600 before being annealed (lines 1614, 1616, 1618, 1620 and 1622) and after being annealed (line 1624). As shown in FIG. 16B, seed layer 1602 and cap layer 1612 are each about 100 at.m, as represented by line 1614 and line 1622, respectively. % Pt may be included. Although not shown in FIG. 16B, seed layer 1602 and / or cap layer 1612 may include other components in addition to or in place of Pt. Further, the seed layer 1602 may include a composition that is different from the cap layer 1612 in some embodiments.

  Returning to FIG. 16B, the first layer 1606 and the third layer 1610 may include more Fe than the seed layer 1602 and the cap layer 1612, as represented by lines 1616 and 1620, respectively. In other examples, the first layer 1606 and the third layer 1610 may comprise an alloy richer in Fe or less rich in Fe than the alloy represented by the lines 1616 and 1620. Then, as indicated by line 1618, the second layer 1608 may include the largest amount of Fe. According to FIG. 16B, the second layer 1608 includes an alloy of Pt and Fe, but in other embodiments, the second layer 1608 may include only Fe or the alloy represented in FIG. 16B. More Fe rich alloys or less Fe rich alloys may be included. As shown in FIGS. 16A and 16B, the bias magnet 1600 is substantially symmetric with respect to a plane 1626 that is approximately equidistant from and substantially parallel to the seed layer 1602 and the cap layer 1612 both before and after annealing. Having a composition profile.

As indicated by line 1624, the annealing of the bias magnet 1600 may result in a blurred or smoothed composition profile compared to the composition profile prior to annealing. As line 1624 shows, the components of individual layers 1602, 1606, 1608, 1610 and 1612 may diffuse between adjacent layers of bias magnet 1600 during annealing. For example, part of Fe in the first layer 1606 may diffuse into the seed layer 1602, and Pt from the seed layer 1602 may diffuse into the first layer 1606. Similar diffusion may occur in other adjacent layers, for example, between the first layer 1606 and the second layer 1608, between the second layer 1608 and the third layer 1610, and the third layer 1610. It may occur between the cap layer 1612. Diffusion of components between adjacent layers of the biasing magnet 1600 may result in a smoother, or blurred composition gradient, the atomic layer ordering to ordering the crystal structure, such as L1 ₀ phase structure May be promoted. FIG. 16B shows a composition profile after annealing that includes rounded steps and is not completely smooth (line 1624), but in other examples, the composition profile may be smoother or less. It may not be smooth. Specific composition profiles after annealing can include many, including, for example, annealing time, annealing temperature, thickness of layers 1602, 1606, 1608, 1610 and 1612, composition of layers 1602, 1606, 1608, 1610 and 1612, etc. It may be a function of parameters. In any case, other composition profiles, both smoother and less smooth, are contemplated by this disclosure.

  As described above, a bias magnet 1600 that includes a higher percentage of Fe may have a higher magnetic moment and a lower coercivity than a bias magnet that includes a lower percentage of Fe. Similarly, a layer containing a higher percentage of Fe may have a higher magnetic moment and a lower coercivity than a layer containing a lower percentage of Fe. As such, the second layer 1608 may have a higher magnetic moment and a lower coercivity than the first layer 1606, the third layer 1610, the seed layer 1602 and the cap layer 1612. In some embodiments, the second layer 1608 may be substantially aligned with the free layer of the read sensor, eg, the free layer 208 (FIG. 2), the seed layer 1602, the first layer 1606, the third layer. 1610 and cap layer 1612 may be proximate to other layers of the sensor, eg, other layers of sensor 218 (FIG. 2). In embodiments such as these, the strength of the magnetic field affecting the layers of the sensor 218 other than the free layer 208 may be reduced, which will improve the read performance of the sensor 218. For example, the described alignment of bias magnet 1600 and sensor 218 will improve the signal-to-noise ratio of the sensor.

  The thickness of each of the seed layer 1602 and cap layer 1612 may range up to about 200 mm, more preferably from about 25 mm to about 125 mm. Multi-layer laminate 1604 may include a total thickness of up to about 400 inches, and in some embodiments, from about 100 inches to about 300 inches. The first layer 1606, the second layer 1608, and the third layer 1610 may have similar or different thicknesses. The thickness of each of the first layer 1606, the second layer 1608 and the third layer 1610 can be up to about 50 mm, and in some embodiments, about 5 mm to about 30 mm, or about 10 mm to about 15 mm thick. May be.

  The seed layer 1602, the first layer 1606, the second layer 1608, the third layer 1610, and the cap layer 1612 are formed by sputtering, ion beam deposition, chemical vapor deposition, physical vapor deposition, molecular beam epitaxy, laser ablation, or the like. It may be formed using. Each of the layers may be formed using the same technique, or at least one of the layers may be formed by a technique different from at least one other of the layers.

  Although FIG. 16A shows a bias magnet 1600 that includes a multilayer stack 1604 that includes three layers 1606, 1608, and 1610, in other embodiments, the multilayer stack includes two layers or more than three layers. You may go out. For example, as shown in FIG. 17A, the bias magnet 1700 may include a multilayer stack 1704 that includes five layers 1706, 1708, 1710, 1712 and 1714. Similar to the bias magnet 1600, the layers of the bias magnet 1700 are substantially equidistant from and substantially the same as the seed layer 1702 and the cap layer 1716, as shown in FIG. 17B, both before and after annealing of the bias magnet 1700. May produce a composition gradient that is substantially symmetric with respect to a plane 1734 that is parallel to.

  As shown in FIGS. 17A and 17B, each of the five layers 1706, 1708, 1710, 1712 and 1714 may have approximately the same thickness. For example, as described above with respect to FIGS. 16A and 16B, the thickness of each of the five layers 1706, 1708, 1710, 1712 and 1714 may be up to about 50 mm. In other examples, each of the five layers 1706, 1708, 1710, 1712 and 1714 may be about 5 to about 30 inches, or about 10 to about 15 inches thick. In some embodiments, at least one of the five layers 1706, 1708, 1710, 1712 and 1714 has a thickness that is different from the thickness of at least one other of the five layers 1706, 1708, 1710, 1712 and 1714. May be.

  In the embodiment shown in FIGS. 17A and 17B, the seed layer 1702 and the cap layer 1716 are approximately 100 at. % Pt is included. In other examples, at least one of seed layer 1702 and cap layer 1716 may be formed from another Pt group element, such as, for example, Pd, Ir, Rh, or Ru, or two or more Pt groups It may be formed from an alloy of elements or may contain at least one element in addition to or as an alternative to the Pt group element. For example, at least one of the seed layer 1702 and the cap layer 1716 may include at least one of Mn, Co, Ir, Fe, etc. in addition to or instead of the Pt group element.

  FIG. 17B illustrates that the first layer 1706 and the fifth layer 1714 include an alloy of Pt and Fe, and more particularly a Pt and Fe alloy containing a high proportion of Pt, ie an alloy rich in Pt. Show. In other examples, at least one of the first layer 1706 and the fifth layer 1714 may include higher atomic percentage Fe or lower atomic percentage Fe, or may include one or more additional elements. It may be included, or may include an alloy of different elements, for example, an alloy of at least two of Pt group elements, Fe, Mn, Co, Ir and the like. Further, although FIG. 17B shows the first layer 1706 and the fifth layer 1714 as including substantially the same composition, in other embodiments, the first layer 1706 and the fifth layer 1714 include different compositions. You may go out. In other examples, at least one of the first layer 1706 and the fifth layer 1714 may include an alloy that includes a high proportion of Fe, ie, an alloy rich in Fe.

  FIG. 17B further includes second layer 1708 and fourth layer 1712 comprising an alloy of Pt and Fe, and more particularly a Pt and Fe alloy containing a high proportion of Fe, ie, an alloy rich in Fe. Show as thing. Again, in other examples, at least one of the second layer 1708 and the fourth layer 1712 may include greater atomic percentage Fe or less atomic percentage Fe, or one or more additional layers. It may contain an element or may contain an alloy of different elements. In some embodiments, at least one of the second layer 1708 and the fourth layer 1712 is a non-Fe alloy alloy, such as about 50 at. An alloy containing less than% Fe may be included. Further, FIG. 17B shows the second layer 1708 and the fourth layer 1712 as including substantially the same composition, but in other embodiments, the second layer 1708 and the fourth layer 1712 include different compositions. You may go out.

  As shown in FIG. 17B, the third layer 1710 may contain substantially only Fe. In other examples, the third layer 1710 may include an alloy of Fe and Pt, may include another element, such as a Pt group, Co, Mn, Ir, or Fe, Co. , Mn, Ir and at least two alloys of Pt group elements may be included. As described above, in some embodiments, it may be desirable for third layer 1710 to have the highest magnetic moment and thus include the highest atomic percentage Fe. The atomic percentage Fe in the third layer may be greater than the atomic percentage Fe in the first layer 1706, the second layer 1708, the fourth layer 1712, and the fifth layer 1714.

  Similar to the bias magnet 1600 (FIG. 16), the layers of the bias magnet 1700 may be formed as substantially separate individual layers. For example, after formation, the seed layer is about 100 at. % Pt, the first layer 1706 may include a Pt rich alloy represented by line 1720, and the second layer 1708 may comprise an Fe rich alloy represented by line 1722. May be included. The third layer 1710 is about 100 at. % Fe may be included. Fourth layer 1712 may include an Fe-rich alloy represented by line 1726, and fifth layer 1714 may include a Pt-rich alloy represented by line 1728, the cap layer. 1716 is about 100 at. % Pt may be included.

After annealing, the composition of the bias magnet 1700 may be represented by line 1732. In particular, annealing of the bias magnet 1700 may result in a composition profile that is blurred or smoothed as compared to the composition profile of the bias magnet 1700 prior to annealing. As line 1732 shows, the components of individual layers 1702, 1706, 1708, 1710, 1712, 1714, 1716 may diffuse into the adjacent layers of bias magnet 1700 during annealing. For example, part of Fe in the first layer 1706 may diffuse into the seed layer 1702, and Pt in the seed layer 1702 may diffuse into the first layer 1706. Similar diffusion may occur between other adjacent layers, for example, between the first layer 1706 and the second layer 1708, between the second layer 1708 and the third layer 1710, and the like. Such diffusion may result in a smoother or blurred composition gradient and may promote ordering of the atoms of the layer into an ordered crystal structure such as the L1 ₀ phase structure. . FIG. 17B shows a composition profile after annealing that includes rounded steps and is not completely smooth (line 1732), but in other examples, the composition profile may be smoother than in FIG. Or it may not be so smooth. Specific composition profiles after annealing include, for example, annealing time, annealing temperature, layer 1702, 1706, 1708, 1710, 1712, 1714, 1716 thickness, layers 1702, 1706, 1708, 1710, 1712, 1714 and 1716 It may be a function of many parameters, including composition and the like. In any case, other composition profiles, both smoother and less smooth, are contemplated by this disclosure.

  FIGS. 18A-18C illustrate an example of a bias magnet 1800 that includes a multilayer stack 1804 between a seed layer 1802 and a cap layer 1816. In contrast to the example shown in FIGS. 16A, 16B, 17A, and 17B, the bias magnet 1800 is substantially equidistant from the seed layer 1802 and the cap layer 1816 and is substantially parallel to the surface 1834. A composition gradient that is asymmetric with respect to. A compositional gradient that is asymmetric with respect to surface 1834 may facilitate control of the portion of the bias magnet 1800 that produces the greatest magnetic field strength. 18B and 18C show an exemplary alignment of bias magnet 1800 (FIG. 18B) and read sensor 1838 (FIG. 18C).

  As shown in FIGS. 18A and 18B, the bias magnet 1800 includes four layers below the face 1834: a seed layer 1802, a first layer 1806, a second layer 1808, and a third layer 1810. Also good. Bias magnet 1800 may further include three layers above surface 1834, a fourth layer 1812, a fifth layer 1814, and a cap layer 1816. In some embodiments, seed layer 1802 and cap layer 1830 may be about 100 at.m. as indicated by line 1818 and line 1830, respectively, in FIG. % Pt may be included. In other embodiments, as described above, at least one of seed layer 1802 and cap layer 1830 includes another element, such as another Pt group element, Fe, Co, Mn, Ir, or the like. Or may contain at least two alloys of these elements.

  As FIG. 18A shows, each of the five layers 1806, 1808, 1810, 1812 and 1814 may comprise a different composition. In some embodiments, the first layer 1806 may be an alloy of Pt and Fe, and more particularly an alloy of Pt and Fe containing a high proportion of Pt, such as an alloy rich in Pt as represented by line 1820. May be included. In other examples, the first layer 1806 may include the larger atomic percentage Fe or the lower atomic percentage Fe shown in FIG. 18A, or may include one or more additional elements. Or an alloy of different elements, for example, an alloy of at least two of Pt group elements, Fe, Mn, Co, Ir and the like. In some embodiments, the first layer 1806 is an Fe-rich alloy, ie, about 50 at. An alloy containing Fe larger than% may be included.

  Line 1822 in FIG. 18A indicates that the second layer 1808 includes an alloy of Pt and Fe, and more particularly an alloy of Pt and Fe that includes a greater atomic percentage Fe than the first layer 1806. Again, in other examples, the second layer 1808 may include the larger atomic percentage Fe or the lower atomic percentage Fe shown in FIG. 18A, or may include one or more additional elements. Or it may contain alloys of different elements. In some embodiments, the second layer 1808 may include an alloy of Pt group elements and Fe including a high proportion of Fe, such as an alloy rich in Fe.

  As shown in FIG. 18A, the third layer 1810 represented in FIG. 18A by line 1824 may comprise an alloy of Pt and Fe with a high proportion of Fe. In other examples, the third layer 1810 may include an alloy of Fe and Pt (including alloys rich in Pt) that includes a greater or lesser percentage of Fe, and other elements, such as It may comprise another Pt group element, Co, Mn, Ir, or at least two alloys of Fe, Co, Mn, Ir and Pt group elements. As FIG. 18A shows, the first layer 1806, the second layer 1808, and the third layer 1810 may each be closer to the seed layer 1802 than the cap layer 1816. That is, the first layer 1806, the second layer 1808, and the third layer 1810 are partially from the surface 1834 that is approximately equidistant from and substantially parallel to the seed layer 1802 and the cap layer 1816. Or it may be located completely below.

  As indicated by line 1826 in FIG. 18A, the fourth layer 1812 may contain substantially only Fe, or substantially only another element such as a Pt group metal, Co, Ir, Mn, etc. May be included. In other examples, the fourth layer 1812 may include at least two alloys of Fe, Co, Ir, Mn, and Pt group metals. In some embodiments, the fourth layer 1812 has the maximum magnetic moment of the first layer 1806, the second layer 1808, the third layer 1810, the fourth layer 1812, and the fifth layer 1814. It may be desired. Thus, the fourth layer 1812 may include the highest atomic percentage Fe, or the highest atomic percentage of another element that provides a high magnetic moment.

  The fifth layer 1814 may include a lower percentage of Fe than the fourth layer 1812. For example, as indicated by line 1828 in FIG. 18A, the fifth layer 1814 is approximately 50 at. % Fe and 50 at. An alloy of Pt and Fe containing% Pt may be included. In other examples, the fifth layer 1814 may include higher atomic percentage Fe or lower atomic percentage Fe. For example, the fifth layer 1814 may include a high proportion of Fe, such as an alloy rich in Fe, or a high proportion of Pt, such as an alloy rich in Pt. In other examples, the fifth layer 1814 may include at least one other element, such as another Pt group element, Co, Ir, Mn, or the like, or Fe, Co, Ir, Mn, Fe, etc. , And may contain at least two alloys such as Pt group elements.

  At least one of the five layers 1806, 1808, 1810, 1812 and 1814 may have a different thickness than at least one other of the five layers 1806, 1808, 1810, 1812 and 1814. For example, as shown in FIGS. 18A and 18B, the first layer 1806, the second layer 1808, and the third layer 1810 may be substantially the same thickness. 18A and 18B further illustrate the fourth layer 1812 and the fifth layer 1814 as being of similar thickness. In other examples, each of the layers may have a different thickness, or each of the layers may have approximately the same thickness. In any case, as described above with respect to FIGS. 16A and 16B, the thickness of each of the five layers 1706, 1708, 1710, 1712 and 1714 may be up to about 50 mm. In other examples, each of the five layers 1706, 1708, 1710, 1712 and 1714 may have a thickness between about 5 and about 30 inches, or between about 10 and about 15 inches.

Similar to bias magnet 1600 (FIGS. 16A and 16B) and bias magnet 1700 (FIGS. 17A and 17B), the layers of bias magnet 1800 may be formed as substantially separate individual layers. For example, after formation, the seed layer 1802 is approximately 100 at. % Pt, the first layer 1806 may include a FePt alloy composition represented by line 1820, and the second layer 1808 may include a FePt alloy composition represented by line 1822. Good. The third layer 1810 may include a FePt alloy composition as indicated by line 1824. The fourth layer 1812 is about 100 at. % Fe may be included. The fifth layer 1814 may include a FePt alloy composition represented by line 1828, and the cap layer 1816 may be about 100 at. % Pt may be included. After annealing, the composition of the bias magnet 1800 may be represented by line 1832. In particular, annealing of the bias magnet 1800 may result in a composition profile that is blurred or smoothed as compared to the composition profile of the bias magnet 1800 prior to annealing. As line 1832 shows, the components of individual layers 1802, 1806, 1808, 1810, 1812, 1814, 1816 may diffuse into the adjacent layers of bias magnet 1800 during annealing. For example, part of Fe in the first layer 1806 may diffuse into the seed layer 1802, and Pt in the seed layer 1802 may diffuse into the first layer 1806. Similar diffusion may occur between other adjacent layers, for example, between the first layer 1806 and the second layer 1808, between the second layer 1808 and the third layer 1810, and the like. Such diffusion may result in a smoother or blurred composition gradient and may promote ordering of the atoms of the layer into an ordered crystal structure such as the L1 ₀ phase structure. . 18A shows a composition profile after annealing that includes rounded steps and is not completely smooth (line 1832), but in other examples, the composition profile may be smoother than in FIG. Or it may not be so smooth. Specific composition profiles after annealing include, for example, annealing time, annealing temperature, layer 1802, 1806, 1808, 1810, 1812, 1814, 1816 thickness, layers 1802, 1806, 1808, 1810, 1812, 1814 and 1816 It may be a function of many parameters, including composition and the like. In any case, other composition profiles, both smoother and less smooth, are contemplated by this disclosure.

  18B and 18C show the alignment of bias magnet 1800 and read sensor 1838. FIG. Read sensor 1838 may be similar to tunneling magnetoresistive sensor 218 shown in FIG. In particular, sensor 1838 may include an antiferromagnetic seed layer 1850, a pinned layer 1848, a reference layer 1846, a tunnel barrier layer 1844, a free layer 1842 and a cap layer 1840. As shown by FIGS. 18B and 18C, the fourth layer 1812 of the bias magnet 1800 may be substantially aligned with the free layer 1842 of the read sensor 1838. As described above, the fourth layer 1812 may include the highest atomic percentage Fe and thus may have the highest magnetic moment. The first layer 1806, the second layer 1808, the third layer 1810, and the fifth layer 1814 may contain a lower atomic percentage Fe than the fourth layer 1812 and thus have a lower magnet moment. May be. By substantially aligning the fourth layer 1812 with the free layer 1842, the magnetic moment of the fourth layer 1812 does not affect the remaining layers of the read sensor 1838 as much as possible, while the magnetic layer of the free layer 1842. You may bias the moment. Further, the magnetic moments of the seed layer 1802, the first layer 1806, the second layer 1808, the third layer 1810, the fifth layer 1814, and the cap layer 1816 may be less than that of the fourth layer 1812. Well, when positioned close to the remaining layers of the read sensor 1838, the remaining layers of the read sensor 1838 may be affected to a lesser extent than a layer having a magnetic moment similar to the fourth layer 1812. Thus, the construction of the bias magnet 1800 may reduce undesirable effects of the magnetic moment of the bias magnet 1800 on layers of the read sensor 1838 other than the free layer 1842.

  As FIG. 18B and FIG. 18C show, the fourth layer 1812 and the free layer 1842 are not strictly aligned. For example, the fourth layer 1812 is thicker than the free layer 1842. In other embodiments, the fourth layer 1812 and the free layer 1842 may be more fully aligned. For example, the fourth layer 1812 and the free layer 1842 may have approximately the same thickness. In other embodiments, the fourth layer 1812 and the free layer 1842 may not be so closely aligned. For example, neither the boundaries of the fourth layer 1812 and the free layer 1842 may be aligned, and the fourth layer 1812 and the free layer 1842 may have different thicknesses.

  18A and 18B illustrate a bias magnet 1800 that includes a multilayer stack 1804 having five layers 1806, 1808, 1810, 1812 and 1814 that include asymmetric composition profiles, but in other embodiments, a bias magnet Includes less than 5 layers or more than 5 layers and may have an asymmetric composition profile. For example, the bias magnet may include four layers or six layers and may have an asymmetric composition profile. Further, the alignment between the bias magnet 1800 and the read sensor 1838 may be different from that shown in FIGS. 18B and 18C. For example, the third layer 1810 and the free layer 1842 may be substantially aligned, or the fifth layer 1814 and the free layer 1842 may be approximately aligned. Other alignments of the bias magnet 1800 and the read sensor 1838 are obvious and are contemplated by the present disclosure.

  In some embodiments, a bias magnet that includes a multilayer stack may not include a composition gradient, but may instead include a substantially uniform composition profile throughout the multilayer stack. For example, as shown in FIGS. 19A and 19B, the bias magnet 1900 may include a multilayer stack 1904 including a seed layer 1902, a cap layer 1916, and five layers 1906, 1908, 1910, 1912 and 1914. Good. 19A and 19B show the bias magnet 1900 as including Pt and Fe. In other embodiments, bias magnet 1900 may include Fe and another Pt group element, such as Pd, Ir, Rh, or Ru, or at least two of Co, Ir, Mn, Fe, and Pt group elements. It may contain one.

  In the embodiment shown, seed layer 1902 and cap layer 1916 are each about 100 at. % Pt is included. In other examples, at least one of seed layer 1902 and cap layer 1916 may be formed from another Pt group element, such as, for example, Pd, Ir, Rh, or Ru, or two or more Pt groups It may be formed from an alloy of elements or may contain at least one element in addition to or as an alternative to the Pt group element. For example, at least one of the seed layer 1902 and the cap layer 1916 may include at least one of Mn, Co, Ir, Fe, etc. in addition to or instead of the Pt group element.

  FIG. 19B illustrates that the first layer 1906, the third layer 1910, and the fifth layer 1914 are made of an alloy of Pt and Fe, and more particularly a Pt and Fe alloy containing a high proportion of Fe, such as Fe. It is shown as containing a rich alloy. In other embodiments, at least one of the first layer 1906, the third layer 1910, and the fifth layer 1914 may include greater atomic percentage Fe or less atomic percentage Fe, or one The above additional elements may be included, or an alloy of different elements, for example, an alloy of at least two of Pt group elements, Fe, Mn, Co, Ir and the like may be included. Further, FIG. 19B shows the first layer 1906, the third layer 1910, and the fifth layer 1914 as including substantially the same composition, but in other embodiments, the first layer 1906, the third layer 1914 At least one of the layer 1910 and the fifth layer 1914 may include different compositions. In other embodiments, at least one of the first layer 1906, the third layer 1910, and the fifth layer 1914 may include an alloy that includes a high proportion of Pt, ie, an alloy that is rich in Pt.

  FIG. 19B further illustrates that the second layer 1908 and the fourth layer 1912 are made of an alloy of Pt and Fe, and more particularly a Pt and Fe alloy containing a high proportion of Pt, ie an alloy rich in Pt. It is shown as including. Again, in other embodiments, at least one of the second layer 1908 and the fourth layer 1912 may include greater atomic percentage Fe or less atomic percentage Fe, or one or more additional layers. It may contain an element or may contain an alloy of different elements. In some embodiments, at least one of the second layer 1908 and the fourth layer 1912 is a non-Fe-rich alloy, such as about 50 at. An alloy containing less than% Fe may be included. Further, although FIG. 19B shows the second layer 1908 and the fourth layer 1912 as including substantially the same composition, in other embodiments, the second layer 1908 and the fourth layer 1912 include different compositions. You may go out.

  Each of seed layer 1902, first layer 1906, second layer 1908, third layer 1910, fourth layer 1912, fifth layer 1914, and cap layer 1916 has a composition different from that shown in FIG. 19B. May be included. For example, at least one of the seed layer 1902, the first layer 1906, the second layer 1908, the third layer 1910, the fourth layer 1912, the fifth layer 1914, and the cap layer 1916 has a larger atomic percentage Fe. Or it may contain less atomic percentage Fe. At least one different composition of the seed layer 1902, the first layer 1906, the second layer 1908, the third layer 1910, the fourth layer 1912, the fifth layer 1914, and the cap layer 1916 can be pre-annealed and / or It may result in a bias magnet having a different composition profile than the later bias magnet 1900.

  Similar to bias magnet 1600 (FIG. 16A), the layers of bias magnet 1900 may be formed as substantially separate individual layers. For example, after formation, the seed layer 1902 is approximately 100 at. % Pt, the first layer 1906 may include an Fe-rich alloy composition represented by line 1920, and the second layer 1908 may be a Pt-rich alloy represented by line 1922. A composition may be included. As indicated by line 1924, third layer 1910 may include an Fe-rich alloy and fourth layer 1912 may include a Pt-rich alloy composition represented by line 1926. , Fifth layer 1914 may include an Fe-rich alloy composition represented by line 1928 and cap layer 1916 may have a thickness of about 100 at. % Pt may be included.

After annealing, the composition of the bias magnet 1900 may be represented by line 1932. In particular, annealing of the bias magnet 1900 may result in a composition profile that is blurred or smoothed as compared to the composition profile of the bias magnet 1900 prior to annealing. As line 1932 shows, the components of individual layers 1902, 1906, 1908, 1910, 1912, 1914, 1916 may diffuse into the adjacent layers of bias magnet 1900 during annealing. For example, part of Fe in the first layer 1906 may diffuse into the seed layer 1902, and Pt in the seed layer 1902 may diffuse into the first layer 1906. Similar diffusion may occur between other adjacent layers, for example, between the first layer 1906 and the second layer 1908, between the second layer 1908 and the third layer 1910, and the like. Such diffusion may result in a smoother or blurred composition gradient and may promote ordering of the atoms of the layer into an ordered crystal structure such as the L1 ₀ phase structure. . FIG. 19B shows an annealed composition profile that includes rounded steps and is not completely smooth (line 1932), but in other examples, the composition profile may be smoother than in FIG. Or it may not be so smooth. Specific composition profiles after annealing include, for example, annealing time, annealing temperature, layer 1902, 1906, 1908, 1910, 1912, 1914, 1916 thickness, layers 1902, 1906, 1908, 1910, 1912, 1914 and 1916. It may be a function of many parameters, including composition and the like. In any case, other composition profiles, both smoother and less smooth, are contemplated by this disclosure.

  In some embodiments, the bias magnet may include a multilayer stack including more than five layers or fewer than five layers. In some embodiments, a multilayer stack including a greater number of layers may reduce the annealing temperature required to form an ordered phase structure as compared to a multilayer stack having fewer layers. Good.

  FIG. 20 is a flowchart of an exemplary technique in which a bias magnet, eg, bias magnet 1600 (FIG. 16A) may be formed. Initially, a seed layer 1602 may be formed (2002). Seed layer 1602 may be formed by any of a variety of techniques, including, for example, sputtering, ion beam evaporation, chemical vapor deposition, physical vapor deposition, molecular beam epitaxy, laser ablation, and the like. Seed layer 1602 may be formed on a variety of substrates, such as insulating material 222 or 223 (FIG. 2), for example. As described above, the seed layer 1602 may have a thickness of up to about 200 mm, and in some embodiments may have a thickness between about 25 mm and about 125 mm.

  Thereafter, a multilayer stack 1604 is formed on the seed layer 1602 (2004). As described with respect to FIGS. 16A and 16B, the multilayer stack 1604 may include two layers, three layers, or more than three layers. The layers in the multilayer stack 1604 may include similar or different compositions. Each of the first layer 1606, the second layer 1608, and the third layer 1610 in the multilayer stack 1604 may be formed individually, and each layer 1606, 1608, 1610 may be formed by, for example, sputtering, ion beam evaporation, chemical It may be formed by vapor deposition, physical vapor deposition, molecular beam epitaxy, laser ablation, or the like. The thickness of each of the first layer 1606, the second layer 1608, and the third layer 1610 may be up to about 50 mm. In some embodiments, at least one of the first layer 1606, the second layer 1608, and the third layer 1610 may have a thickness between about 5 and about 30 inches. In an example, at least one of the first layer 1606, the second layer 1608, and the third layer 1610 may have a thickness between about 5 and about 15 inches.

  Once the layer of the multilayer stack 1604 is formed, a cap layer 1612 may be formed on the multilayer stack 1604 (2006). The cap layer 1612 may be formed by, for example, sputtering, ion beam evaporation, chemical vapor deposition, physical vapor deposition, molecular beam epitaxy, laser ablation, or the like. As described above, the thickness of the cap layer 1612 may be up to about 200 inches, and in some embodiments may have a thickness between about 25 inches and about 125 inches.

Finally, the bias magnet 1600 may be annealed (2008). For example, the bias magnet 1600 may be annealed at a temperature in the range of about 200 ° C. to about 500 ° C. within about 6 hours. In some embodiments, the bias magnet 1600 may be annealed at a temperature of about 200 ° C. to about 300 ° C., or about 280 ° C. In some embodiments, annealing may be about 4 hours. Annealing the bias magnet 1600 may facilitate diffusion of at least one component between adjacent layers of the bias magnet 1600. Such diffusion may facilitate the formation of a regularized phase, such as the L1 ₀ ordered phase. Such diffusion may result in an even more uniform composition, such as FIGS. 19A and 19B, or a smoother composition gradient, such as FIGS. 16A, 16B, 17A, 17B, 18A, and FIG. You may return to 18B.

  FIG. 21 is a plot of magnetic moment versus magnetic field for four different iron-platinum hard magnets. Curve 2102 represents the residual coercivity of a hard magnet including a Pt seed layer, Fe rich FePt alloy interlayer and Pt cap layer annealed at about 280 ° C. Curve 2104 shows a 10 Pt seed layer, 40 at. % Fe and 60 at. 10% layer containing% Pt, 65 at. % Fe and 35 at. 150% layer containing% Pt, 40 at. % Fe and 60 at. It represents the coercive force of a hard magnet including a 10% layer containing% Pt and a 10% Pt cap layer. Curve 2106 represents the residual coercivity of a hard magnet including a Pt seed layer, an Fe rich FePt alloy interlayer and a Pt cap layer annealed at about 300 ° C. Curve 2108 shows a 10 Pt seed layer, 40 at. % Fe and 60 at. 10% layer containing% Pt, 65 at. % Fe and 35 at. 150% layer containing% Pt, 40 at. % Fe and 60 at. It represents the coercive force of a hard magnet including a 10% layer containing% Pt and a 10% Pt cap layer.

  As FIG. 21 shows, the hard magnet represented by curve 2108 had a residual coercivity that was approximately 1400 Oe, which was greater than the coercivity of the hard magnet represented by curve 2106. This indicates that when annealed at approximately the same temperature, the multilayer stack will result in a hard magnet having a larger coercivity than a hard magnet including a single intermediate layer.

  Curves 2104 and 2106 show that a hard magnet comprising a multi-layer laminate annealed at a temperature of about 280 ° C. has a residual coercivity comparable to that of a hard magnet having a single intermediate layer annealed at about 300 ° C. Indicates that you will have Thus, a comparison of curves 2104 and 2106 indicates that the chemical ordering temperature may be lowered by utilizing a multilayer stack between the seed layer and the cap layer.

  Various embodiments of the invention have been described. The implementations described above and other implementations are within the scope of the following claims.

  1600 Bias magnet, 1602 Seed layer, 1604 Multilayer stack, 1606 First layer, 1608 Second layer, 1610 Third layer, 1612 Cap layer.

Claims (20)

A seed layer comprising a first component comprising at least one of a Pt group metal, Fe, Mn, Ir, and Co;
A cap layer comprising the first component;
A multilayer laminate between the seed layer and the cap layer;
The multilayer stack includes a first layer including the first component and a second component including at least one of a Pt group metal, Fe, Mn, Ir, and Co, and the second component Is different from the first component, the multilayer laminate is further formed on the first layer and formed on the second layer, the second layer including the second component, and the first layer. And a third layer containing the second component.   The hard magnet according to claim 1, wherein the first component includes a Pt group metal and the second component includes Fe.   The hard magnet according to claim 2, wherein the Pt group metal includes Pt.   The first layer includes Fe containing a lower atomic percentage of Fe than the second layer and the first alloy of the Pt group metal, and the third layer has a lower atomic percentage than the second layer. The hard magnet according to claim 2, wherein the hard magnet includes Fe including Fe and a third alloy of the Pt group metal.   The multilayer laminate further includes a fourth layer formed on the first layer and a fifth layer formed on the fourth layer, wherein the fourth layer includes the first layer. A fourth alloy of Fe and a Pt group metal comprising an atomic percentage of Fe that is larger than one alloy and smaller than the second layer, and the fifth layer has a larger atomic percentage than the fourth alloy. The hard magnet according to claim 4, comprising Fe containing Fe and a fifth alloy of the Pt group metal.   The hard magnet of claim 1, wherein the composition profile of the hard magnet is substantially symmetric with respect to a plane that is substantially equidistant from and substantially parallel to the seed layer and the cap layer.   The hard magnet of claim 1, wherein the composition profile of the hard magnet is asymmetric with respect to a plane that is approximately equidistant from and substantially parallel to the seed layer and the cap layer.   The hard magnet of claim 1, wherein at least one of the first layer, the second layer, and the third layer has a thickness of between about 10 to about 15 inches. A hard layer comprising a seed layer comprising a Pt group metal, a cap layer comprising the Pt group metal, and a multilayer stack between the seed layer and the cap layer;
The multilayer stack includes a first layer including a first alloy of Fe and Pt group metal, a second layer including Fe and formed on the first layer, and Fe and Pt group metal. A read / write head for a data storage device, comprising a third layer comprising a second alloy and formed on the second layer.   The read / write head of claim 9, wherein at least one of the first layer, the second layer, and the third layer has a thickness of up to about 50 inches.   The read / write head of claim 9, wherein at least one of the first layer, the second layer, and the third layer has a thickness between about 10 inches and about 15 inches.   The read / write head of claim 9, further comprising a read sensor including a free layer, wherein the second layer is substantially aligned with the free layer.   The read / write of claim 9, wherein the first alloy comprises a lower atomic percentage Fe than the second layer, and the third alloy comprises a lower atomic percentage Fe than the second layer. head.   The multilayer laminate further includes a fourth layer formed on the first layer and a fifth layer formed on the fourth layer, wherein the fourth layer includes the first layer. A fourth alloy of Fe and a Pt group metal comprising an atomic percentage of Fe that is larger than one alloy and smaller than the second layer, and the fifth layer has a larger atomic percentage than the fourth alloy. The read / write head of claim 13, comprising Fe containing Fe and a fifth alloy of the Pt group metal.   The read / write head of claim 14, further comprising a read sensor including a free layer, wherein the second layer is substantially aligned with the free layer.   The read / write head of claim 9, wherein the composition profile of the hard magnet is substantially symmetric with respect to a plane that is substantially equidistant from and substantially parallel to the seed layer and the cap layer.   The read / write head of claim 9, wherein the composition profile of the hard magnet is asymmetric with respect to a plane that is approximately equidistant from and substantially parallel to the seed layer and the cap layer. Forming a seed layer comprising a first component comprising at least one of a Pt group metal, Fe, Mn, Ir, and Co;
Forming a multi-layer stack on the seed layer, the multi-layer stack including the first component and at least one of a Pt group metal, Fe, Mn, Ir, and Co. A first layer including a component, wherein the second component is different from the first component, and the multilayer stack is further formed on the first layer and includes the second component. And a third layer formed on the second layer and including the first component and the second component, and
Forming a cap layer on the multilayer stack, the cap layer comprising the first component;
Heating the seed layer, the multilayer stack, and the cap layer to an annealing temperature to cause interdiffusion between adjacent layers of the seed layer, the multilayer stack, and the cap layer.   The method of claim 18, wherein the first component comprises a Pt group metal and the second component comprises Fe.   The method of claim 18, wherein heating the multilayer structure to an annealing temperature comprises heating the multilayer structure between about 250 degrees Celsius and about 300 degrees Celsius.