JPH08335515A - Multilayer magnetoresistive film and magnetic head - Google Patents

Abstract

(57) [Summary] [Structure] The thickness of the non-magnetic layer of the multilayer film including the magnetic layer and the non-magnetic layer having a high magnetoresistive effect is thin in the portion close to the substrate 11 and thick in the portion far from the substrate 11. Further, the magnetoresistive effect element was used in a magnetic head and a magnetic recording / reproducing apparatus. [Effect] By controlling the thickness of the non-magnetic layer, it is possible to cope with an effective change in the layer thickness due to the unevenness of the multilayer film, and it is possible to obtain a multilayer film exhibiting a high magnetoresistance change rate, and a high reproduction output is exhibited. It was

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer film having a high magnetoresistive effect, a magnetoresistive effect element using the same, a magnetic head and a magnetic recording / reproducing apparatus.

[0002]

2. Description of the Related Art As the magnetic recording density increases, a material having a high magnetoresistive effect is required as a magnetoresistive effect material used for a reproducing magnetic head. "(001)" described in Physical Review Letters, Vol. 61, No. 21, pp. 2472-2475.
Giant magnetoresistance effect of Fe / (001) Cr magnetic superlattice
nt Magnetoresistance of (001) Fe / (001)
Cr magnetic superlattices) ", a magnetic film having a multilayer structure (Fe / Cr multilayer film) has about 50
% Magnetoresistance change (at 4.2K) is reported.

[0003]

The Ni--Fe / Cu multilayer film having a structure similar to that of the Fe / Cr multilayer film has a relatively high magnetoresistive change rate, but in a laminated structure having a low saturation magnetic field, There is a problem that the rate of resistance change is insufficient.

An object of the present invention is to provide a method for easily improving the magnetoresistance change rate of a multilayer film.

[0005]

The present inventors have found that the magnetic layer,
As a result of intensive studies on a multilayer film in which a non-magnetic layer is laminated, it was found that the flatness of each layer of the multilayer film deteriorates as the multilayer film grows, and the present invention has been completed.

That is, in the present invention, in the multilayer film as described above, the non-magnetic layer is made thicker as the distance from the substrate increases.

[0007]

In general, in a multilayer film, the flatness of each layer is good in the portion close to the substrate, but the unevenness increases as the distance from the substrate increases. When the unevenness of the non-magnetic layer increases, the substantial thickness of the non-magnetic layer felt by the electrons passing through the non-magnetic layer becomes smaller than the thickness of the non-magnetic layer in the film thickness direction. Therefore, in a multilayer film showing a high magnetoresistance change rate only in a region where the thickness of the non-magnetic layer is very narrow, it is necessary to thicken the non-magnetic layer above the film with increased unevenness. The magnetoresistive effect element using the multilayer film whose layer thickness is controlled as described above is suitable for a magnetic head or the like,
Further, by using the above magnetic head, a high performance magnetic recording / reproducing apparatus can be obtained.

[0008]

【Example】

Example 1 The structure of a standard multilayer film is shown in FIG. As a conventional example, the buffer layer 1 is formed on the substrate 11 made of Si.
A Fe layer having a thickness of 5 nm was formed as No. 2, and a Ni-20 at% Fe alloy layer having a thickness of 1.0 nm as the magnetic layer 13 and a Cu layer having various thicknesses as the nonmagnetic layer 14 were alternately laminated thereon. . The number of stacking cycles is 20. An ion beam sputtering device was used to form the multilayer film. The sputtering conditions are an Ar pressure of 0.02 Pa, an ion gun acceleration voltage of 300 V, and an ion current of 30 mA. However, Fe
When forming the layer, the ion current was set to 60 mA.

FIG. 2 shows the relationship between the Cu nonmagnetic layer thickness and the magnetoresistance change rate of the multilayer film. As shown in the figure, the multilayer film exhibits a high magnetoresistance change rate only when the thickness of the nonmagnetic layer is specific. This is because when the thickness of the non-magnetic layer is large, an exchange interaction acts between the magnetic layers to make the directions of magnetization antiparallel. When the exchange interaction works, the magnetization directions of the magnetic layers alternate with each other when no magnetic field is applied to the multilayer film. At this time, the electrical resistivity of the multilayer film is high. When a magnetic field is applied to the multilayer film and the directions of magnetization become parallel, the electrical resistivity of the multilayer film decreases. This is the magnetoresistive effect in the multilayer film.

As described above, in the multilayer film, a high magnetoresistance change rate can be obtained only when the thickness of the nonmagnetic layer is specific.
In the result of FIG. 2, the peak of the magnetoresistance change rate is seen when the nonmagnetic layer thickness is 1.0, 2.2, 3.8 nm. At the first peak (nonmagnetic layer thickness 1.0 nm), the rate of change in magnetoresistance is high. However, at this time, the exchange interaction that makes the directions of magnetization acting between the magnetic layers antiparallel is very strong, and the directions of magnetization of the multilayer film could not be made parallel unless a high magnetic field of 2.8 kOe was applied. . This indicates that the magnetoresistive effect does not occur unless a high magnetic field is applied in this layer thickness region.

In the region where a relatively high magnetoresistance change rate can be obtained and the saturation magnetic field is low, the second peak (the nonmagnetic layer thickness 2.
2 nm). The saturation magnetic field in this region was 160 Oe. Therefore, when the multilayer film is used for the magnetoresistive head, this non-magnetic layer thickness of the second peak is used.

Now, as shown in FIG. 2, the interval between the first and second peaks of the magnetoresistance change rate is 1.2 nm. On the other hand, the interval between the second and third peaks is 1.6 nm, which is wider than the above interval. The cause of this is considered as follows. When the non-magnetic layer in the multilayer film becomes thicker, the film thickness of the entire multilayer film becomes thicker. Therefore, in the upper portion of the multilayer film, the flatness of each layer deteriorates and unevenness occurs. When unevenness occurs in the multilayer film, as shown in FIG. 3, the thinnest layer thickness 32 is thinner than the layer thickness 31 in the film thickness direction. The layer thickness 31 is a design value, and the nonmagnetic layer thickness in FIG. 2 is this value. Further, generally, when forming a multilayer film, the layer thickness 31 is controlled. On the other hand, the nonmagnetic layer thickness felt by the electrons passing through the nonmagnetic layer is the layer thickness 32. This is because the electrons do not flow in the film thickness direction but in various directions. Exchange interaction between magnetic layers is caused by conduction electrons. Therefore, if the layer thickness 32 does not reach a specific value, the exchange interaction that makes the magnetization directions antiparallel does not work, and the magnetoresistive effect does not occur. Therefore, the peak shifts to the thick nonmagnetic layer thickness region where the layer thickness 32 becomes thicker.

It is considered that the above-mentioned problem of flatness occurs even in the second peak region actually used. Therefore, in this example, a multilayer film was formed in which the thickness of the non-magnetic layer was changed stepwise.

In this embodiment, first, in the structure of FIG. 1, a Ni—O type buffer layer 12 having a thickness of 5 nm was formed on a substrate 11 made of Si. Although NiO was used as the sputtering target, it is considered that the composition of the buffer layer formed by sputtering deviates from the stoichiometric composition. The sputtering conditions are an Ar pressure of 0.02 Pa, an ion gun acceleration voltage of 900 V, and an ion current of 120 mA. The substrate on which the Ni—O-based buffer layer was formed was once taken out from the ion beam sputtering apparatus and then returned to the inside of the apparatus. Further, a thickness of 1.5 is formed on the Ni—O based buffer layer 12 formed on the substrate 11.
nm magnetic layers 13 made of a Ni—Fe—Co alloy and nonmagnetic layers 14 made of Cu were alternately laminated. The thickness of the non-magnetic layer 14 is 2.2 nm up to a stacking period of 5 cycles,
On top of that, the thickness was 2.3 nm. The number of magnetic layers 13 is 1.
It is layer 0. The sputtering conditions are Ar pressure 0.02
Pa, ion gun acceleration voltage 300V, ion current 30
mA. The sputtering target for forming the Ni—Fe—Co magnetic layer includes Ni-16 at% Fe-18 at.
An alloy target having a composition of% Co was used.

The above sample is referred to as sample A. Further, the nonmagnetic layer is formed by the same method as the above-mentioned sample A, and the thickness of the nonmagnetic layer is 1 to 3.
2.1 nm in the period, 2.2 nm in the 4 to 6 period, 7 to 9
A sample having a thickness of 2.3 nm up to the period is referred to as sample B (the number of magnetic layers 13 is 10, so the number of nonmagnetic layers 14 is 9).
layer). Further, as a comparative example, a sample C in which the thickness of the nonmagnetic layer 14 was 2.2 nm and was constant was also formed.

When the magnetoresistance change rates of the above-mentioned samples were measured, the magnetoresistance change rates of sample A and sample B were 12.2% and 13.5%, respectively, which were the same as those of sample C of the conventional example. The rate of change in magnetic resistance was higher than 9.8%. It is considered that this is because the optimum nonmagnetic layer thickness differs depending on the distance of each layer of the multilayer film from the substrate. The saturation magnetic field of the sample and the sample B was about 25 Oe.

In this embodiment, Ni is used as the magnetic layer material.
Although the —Fe—Co alloy was used, other magnetic layer materials can be used. However, it is desirable that the magnetic layer material be soft magnetic. For this purpose, Ni—Fe based alloys and Ni—Fe—Co based alloys are preferable. Although Cu is used as the non-magnetic layer material in this embodiment, Au, Ag, or an alloy containing Cu, Au, or Ag as a main component may be used. However, it is difficult to form the Au and Ag layers as thin and uniform layers. Therefore, Cu and C
It is preferable to use an alloy containing u as a main component.

Example 2 The multilayer film of sample B described in Example 1 was processed into a magneto-sensitive portion shape of a magnetoresistive effect element by a photolithography process. The length of the multilayer film in the track width direction was 2 μm, and the length of the multilayer film in the in-plane direction perpendicular to the track width direction was 1 μm. Further, by the lift-off method, as shown in FIG. 4, the electrode 15 made of Cu was formed at the end of the multilayer film. Further, the insulating layer 21 was formed on the multilayer film, and the permanent magnet layer 22 was further laminated. Insulating layer 21
Are necessary to prevent electrical shorts between the electrodes. Further, the permanent magnet layer 22 is used for the purpose of applying a bias magnetic field to the multilayer film and controlling the operating magnetic field of the magnetoresistive effect element. In this example, Al ₂ O ₃ and Co—Pt alloy were used as the insulating layer 21 and the permanent magnet layer 22, respectively. Further, the magnetoresistive effect element was sandwiched between two shield layers with an insulator made of Al ₂ O ₃ interposed therebetween.

When a magnetic field was applied to the magnetoresistive effect element and a change in electric resistivity was measured, the magnetoresistive effect element using the multilayer magnetoresistive effect film of the present invention was 2.4 kA / m (30).
A magnetic resistance change rate of about 12% was shown with an applied magnetic field of about Oe). Further, the reproduction output of the magnetoresistive element of the present invention is
The value was 3.7 times that of the magnetoresistive element using the Ni-Fe single layer film.

Example 3 A magnetic head was produced using the magnetoresistive effect element described in Example 2. The structure of the magnetic head is shown below. FIG. 5 is a perspective view when a part of the recording / reproducing separated type head is cut. The portion of the multilayer magnetoresistive effect film 61 sandwiched by the shield layers 62 and 63 functions as a reproducing head, and the portions of the lower magnetic pole 65 and the upper magnetic pole 66 that sandwich the coil 64 function as a recording head. Further, a material having a multilayer structure of Cr / Cu / Cr is used for the electrode 68.

The manufacturing method of this head will be described below. Al
_A sintered body containing ₂ O ₃ .TiC as a main component was used as the slider substrate 67. A Ni-Fe alloy formed by a sputtering method was used for the shield layer and the recording magnetic pole. The thickness of each magnetic film was as follows. The upper and lower shield layers 62 and 63 are 1.0 μm, the lower magnetic pole 65 and the upper part 66 are 3.0 μm, and the gap material between the layers is Al formed by sputtering.
₂ O ₃ was used. The film thickness of the gap layer is 0.2 μm between the shield layer and the magnetoresistive effect element, and 0.4 μm between the recording magnetic pole.
m. Further, the distance between the reproducing head and the recording head was set to about 4 μm, and this gap was also formed of Al ₂ O ₃ . Cu having a film thickness of 3 μm was used for the coil 64.

When recording / reproducing was performed with the magnetic head having the structure described above, a reproducing output 3.1 times higher than that of the magnetic head using the Ni--Fe single layer film was obtained. It is considered that this is because the magnetic head of the present invention uses a multilayer film having a high magnetoresistive effect. Also, no large noise was found in the reproduced waveform.

<Embodiment 4> Using the magnetic head of the present invention described in Embodiment 3, a magnetic disk device was manufactured. The structure of the device is shown in FIG. For the magnetic recording medium 71, a material made of a Co—Ni—Pt—Ta alloy having a residual magnetic flux density of 0.75T was used. The recording track width of the magnetic head 73 is 3μ.
m. Since the magnetoresistive effect element in the magnetic head 73 has a high reproduction output, a high-performance magnetic disk device which does not burden the signal processing was obtained.

[0024]

By making the non-magnetic layer thin in the lower part of the multilayer film and thickening the non-magnetic layer in the upper part of the multilayer film with increased irregularities, a multi-layered magnetoresistive film showing a high magnetoresistance change rate was obtained. Furthermore, the magnetoresistive effect element using the multilayer magnetoresistive effect film is suitable for a magnetic field sensor, a magnetic head, and the like.
Further, by using the magnetic head, a high performance magnetic recording / reproducing device can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a multilayer magnetoresistive effect film.

FIG. 2 is a graph showing the rate of change in magnetoresistance depending on the thickness of a Cu nonmagnetic layer in a multilayer film.

FIG. 3 is an explanatory diagram showing a substantial reduction in nonmagnetic layer thickness due to unevenness of a multilayer film.

FIG. 4 is a sectional view showing the structure of a magnetoresistive effect element according to an example of the present invention.

FIG. 5 is a perspective view showing a structure of a magnetic head according to an embodiment of the present invention.

FIG. 6 is an explanatory diagram of a magnetic recording / reproducing apparatus according to an embodiment of the present invention.

[Explanation of symbols]

11 ... Substrate, 12 ... Buffer layer, 13 ... Magnetic layer, 14 ...
Nonmagnetic layer, 15 ... Electrode, 21 ... Insulating layer, 22 ... Permanent magnet layer.

Claims (9)

[Claims] 1. In a multilayer film in which magnetic layers and nonmagnetic layers formed on a substrate or on the substrate via another substance are alternately laminated, the thickness of the nonmagnetic layer in the film thickness direction is ,
A multi-layer magnetoresistive effect film, which is changed according to a distance from the substrate. 2. The multilayer magnetoresistive film according to claim 1, wherein the non-magnetic layer has a larger thickness in the film thickness direction as the distance from the substrate increases. 3. The multilayer magnetoresistive film according to claim 1, wherein the magnetic layer is a Ni—Fe based alloy or a Ni—Fe—Co based alloy. 4. The multilayer magnetoresistive film according to claim 1, wherein the nonmagnetic layer is made of Cu or an alloy containing Cu as a main component. 5. A multilayer magnetoresistive effect film in which the multilayer magnetoresistive effect film according to claim 1, 2, 3 or 4 is formed on a buffer layer made of Ni—O. 6. A magnetoresistive effect element comprising the multilayer magnetoresistive effect film according to claim 1, 2, 3, 4 or 5 and a pair of electrodes. 7. A magnetoresistive head comprising the magnetoresistive element according to claim 6 and a shield layer. 8. A composite magnetic head in which the magnetoresistive head according to claim 7 and an inductive magnetic head are combined. 9. A magnetic recording / reproducing apparatus using the magnetic head according to claim 7.