JP2007109807A - Magnetoresistive element, magnetic head, and magnetic recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetoresistive element which generates low level noise and assures excellent anti-external magnetic field strength, and also to provide a magnetic head and a magnetic recording device. <P>SOLUTION: The magnetoresistive element comprises a lower electromagnetic shield layer and an upper electromagnetic shield layer functioning as electrode and electromagic shield, and a magnetoresistive film held between these two electromagnetic shield layers. The element can feed electrical power in the direction perpendicular to the film surface of the same magnetoresistive element. At least any of these two electromagnetic shield layers is formed of three layers of soft magnetic film/non-magnetic film/soft magnetic film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetoresistive element for reproducing (reading) magnetic information in a magnetic recording apparatus, a magnetic head and a magnetic recording apparatus for recording (writing) or reproducing magnetic information, and in particular, a so-called magnetoresistive film. The present invention relates to a magnetoresistive effect element having a film-perpendicular-to-plane (CPP) structure in which a sense current is passed in the stacking direction using a magnetic tunnel junction film (also referred to as a spin valve film).

  Conventionally, a magnetoresistive element has been used as a reproducing element for reproducing information recorded on a magnetic recording medium in a magnetic head of a magnetic recording apparatus. As the magnetoresistive effect element is increased, the one having a magnetoresistive effect film having high magnetic field sensitivity is becoming mainstream as the recording density is increased. The magnetoresistive film includes two ferromagnetic layers, that is, a magnetization fixed layer whose magnetization is fixed by an antiferromagnetic layer, and a magnetization free layer whose magnetization direction changes according to the leakage magnetic field from the magnetic recording medium. The

  Until now, a CIP (Current-In-Plane) structure in which a sense current flows in the in-plane direction of the magnetoresistive effect film has been mainly used. However, recently, in order to further increase the recording density, a CPP structure in which a sense current is passed in the stacking direction of the magnetoresistive effect film has been proposed, and research is actively conducted as a next-generation reproducing element (for example, (See Patent Document 1).

  In the magnetoresistive effect film having the CPP structure, the signal output flows the sense current Is in the stacking direction of the magnetoresistive effect film having the CPP structure, and the magnetization fixed layer exists between the magnetization of the magnetization free layer and the nonmagnetic intermediate layer. The change in the magnetic resistance according to the relative direction of the magnetization of the second ferromagnetic layer is detected as a voltage change that occurs across the magnetoresistive film. For example, the fixed magnetization layer includes two ferromagnetic layers (a first ferromagnetic layer made of a soft magnetic material and a second ferromagnetic layer made of a soft magnetic material) antiferromagnetically via a nonmagnetic coupling layer. It has a laminated laminated ferri structure. In this laminated ferrimagnetic structure, the magnetizations of the two ferromagnetic layers are antiparallel to each other, so the magnitude of the net magnetization is reduced, the demagnetizing field is reduced, and the net magnetization is suppressed while suppressing the net magnetization. The exchange coupling can be increased and the magnetization direction of the magnetization fixed layer can be reliably fixed.

At this time, the sense current Is, to which no current has previously flowed, flows through the electromagnetic shield layer that functions as an electromagnetic shield that absorbs the signal magnetic field from the adjacent bit, and the electromagnetic shield layer has a medium magnetic field from the adjacent bit. At the same time as the absorption of light, it functions as a sense current electrode.
JP 2002-208744 A (Claims)

  The electromagnetic shield layer is usually formed of a single-layer soft magnetic film. However, the magnetic domain is formed from the magnetic domain formed in the electromagnetic shield layer, for example, the magnetic domain of the electromagnetic shield formed in the recess of the magnetoresistive effect film and the magnetic domain control film described later. There is a problem that the performance of the magnetoresistive effect element is deteriorated due to a static magnetic field leaking to the resistance effect film side.

  In order to solve this problem, it is necessary to suppress the occurrence of local magnetic domains in the electromagnetic shield layer that degrade the performance of the magnetoresistive film. However, the current single-layer electromagnetic shield solves the above problem. I can't.

  An object of the present invention is to solve this problem and to provide a technique for suppressing the generation of local magnetic domains in the electromagnetic shield layer that lowers the performance of the magnetoresistive film. Other objects and advantages of the present invention will become apparent from the following description.

  In the present invention, since the electromagnetic shield layer has a three-layer structure, the current magnetic field is positively utilized, and the local current that lowers the performance of the magnetoresistive effect film in the electromagnetic shield layer by the current magnetic field generated from the sense current Is. Suppresses the occurrence of magnetic domains.

  According to one aspect of the present invention, the magnetoresistive effect film includes a lower electromagnetic shield layer and an upper electromagnetic shield layer that function as an electrode and an electromagnetic shield, and a magnetoresistive effect film sandwiched between the two electromagnetic shield layers. A magnetoresistive effect element capable of energizing in a direction perpendicular to the film surface of the film, wherein at least one electromagnetic shield layer is formed of three layers of soft magnetic film / nonmagnetic film / soft magnetic film An element is provided. According to the aspect of the present invention, a magnetoresistive element having low noise and excellent external magnetic field resistance can be obtained.

  The two electromagnetic shield layers are both formed of a soft magnetic film / non-magnetic film / soft magnetic film, and the magnetoresistive film has a magnetization direction substantially fixed in one direction. Including a magnetization fixed layer having a ferromagnetic film formed thereon, a nonmagnetic intermediate layer, and a magnetization free layer made of a ferromagnetic film whose magnetization direction changes in response to an external magnetic field. It is possible to energize in the vertical direction, at least one of the soft magnetic films is made of a soft magnetic material which may be a high resistance amorphous soft magnetic material, and the soft magnetic material is made of NiFe or CoNbZr In the case of a high resistance amorphous soft magnetic material, it is FeCuNbSiB, the specific resistance of at least one of the soft magnetic films is 25 μΩcm or more, and the thickness of one layer of the soft magnetic film Is 40% or more of the total thickness of the electromagnetic shielding layer comprising the soft magnetic film, the specific resistance of at least one of the nonmagnetic films is 2.1 μΩcm or less, and the nonmagnetic At least one of the films is made of Au, Ag or Cu, and the thickness of one layer of the nonmagnetic film is 20% or less of the total thickness of the electromagnetic shield layer including the nonmagnetic film. It is preferable.

  According to still another aspect of the present invention, there are provided a magnetic head including the magnetoresistive element and a magnetic recording apparatus including the magnetic head. According to the aspect of the present invention, a magnetic head and a magnetic recording apparatus having low noise and excellent external magnetic field resistance can be obtained.

  According to the present invention, a magnetoresistive effect element, a magnetic head, and a magnetic recording apparatus having low noise and excellent external magnetic field resistance can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings, examples and the like. In addition, these figures, Examples, etc. and description illustrate the present invention, and do not limit the scope of the present invention. It goes without saying that other embodiments may also belong to the category of the present invention as long as they match the gist of the present invention. In the drawings, the same reference numeral represents the same element. The dimensions for each element in the figure reflect the actual dimensions and are not scaled. For example, the thickness of the magnetoresistive film is generally about 0.05 μm, and the thickness of the electromagnetic shield layer is about 1 to 2 μm, but the magnetoresistive film is drawn larger for easy understanding. It is.

  A magnetoresistive effect element according to the present invention comprises a lower electromagnetic shield layer and an upper electromagnetic shield layer that function as an electrode and an electromagnetic shield, and a magnetoresistive effect film sandwiched between these two electromagnetic shield layers. A magnetoresistive effect element that can be energized in the direction perpendicular to the film surface (ie, CPP type), and at least one of these two electromagnetic shield layers is a soft magnetic film / non-magnetic film / soft magnetic film It is formed by three layers. That is, a nonmagnetic film for concentrating current is inserted in the middle of a conventional single-layer electromagnetic shield layer.

  According to the present invention, it is possible to make the current magnetic field in the in-layer direction uniform in the electromagnetic shield layer, thereby suppressing the generation of local magnetic domains that deteriorate the performance of the magnetoresistive effect film in the electromagnetic shield layer. The performance degradation of the magnetoresistive element due to the leakage magnetic field leaking from the layer to the magnetoresistive film side can be prevented. Further, accompanying this, generation of a static magnetic field due to the convex and concave portions of the magnetoresistive effect film and the magnetic domain control film described later can be suppressed. Thus, according to the present invention, a magnetoresistive element having low noise and excellent external magnetic field resistance can be obtained.

  The effect of the present invention can be obtained if at least one of the electromagnetic shield layers is formed of three layers of soft magnetic film / nonmagnetic film / soft magnetic film. May be formed of three layers of soft magnetic film / nonmagnetic film / soft magnetic film, and is more preferable. When only one of them is formed of three layers of a soft magnetic film / non-magnetic film / soft magnetic film, there is a stronger demand for the stability of the magnetic domain and the magnetic field at the time of writing information is the upper electromagnetic shield layer. Therefore, it is often preferable to form the upper electromagnetic shield layer in three layers because the magnetic domain is strongly disturbed.

  Next, the structure of the electromagnetic shielding layer according to the present invention will be described with reference to FIGS. 1A is a schematic perspective view of the structure of the electromagnetic shielding layer according to the present invention, and FIG. 1B is a view of the electromagnetic shielding layer in the Z direction (from the ABS surface (air bearing surface)). The figure seen}. As shown in FIGS. 1A and 1B, the two electromagnetic shield layers 28 and 32 according to the present invention each have a three-layer structure. That is, the lower electromagnetic shield layer 28 is composed of two soft magnetic films 28a and a single nonmagnetic film 28b, and the upper electromagnetic shield layer 32 is composed of two soft magnetic films 32a and a single nonmagnetic film 32b. Yes. With such a structure, it is possible to suppress the generation of local magnetic domains that degrade the performance of the magnetoresistive film in the electromagnetic shield layer due to the current magnetic field from the sense current Is that flows concentratedly in the nonmagnetic film. . 1A and 1B, a white thick arrow indicates the direction of magnetization, and a straight thick arrow that is not white indicates the direction of the sense current Is. In FIG. 1-B, a circle including “X” means that the sense current is flowing toward the paper surface, and a circle including a black circle means that the sense current is flowing out from the paper surface. A curved arrow represents a current magnetic field generated by the sense current. In this way, the current magnetic field generated from the sense current Is represented by the curved arrow can be positively utilized to make the current magnetic field in the in-layer direction uniform in the electromagnetic shield layer. In the electromagnetic shield layer, the generation of local magnetic domains that reduce the performance of the magnetoresistive film is suppressed.

  The magnetoresistive film according to the present invention includes a magnetization fixed layer having a ferromagnetic film whose magnetization direction is substantially fixed in one direction, a nonmagnetic intermediate layer, and a magnetization direction that changes according to an external magnetic field. It is preferable that current can be passed in a direction perpendicular to the film surfaces of these layers. By adopting such a spin valve structure, it is possible to obtain a magnetoresistive effect element and a magnetic head having low noise and excellent external magnetic field resistance.

  Next, a composite type magnetic head provided with a magnetoresistive effect element and an induction type recording element according to the present invention will be described with reference to FIGS. A magnetoresistive effect element according to the present invention for reading magnetic information is combined with an inductive magnetic recording element for writing magnetic information to form a composite magnetic head. FIG. 3 shows an example of the structure of such a composite magnetic head. The lower electromagnetic shield layer 28 is composed of two soft magnetic films 28a and one nonmagnetic film 28b, and the upper electromagnetic shield layer 32 is formed of two layers. It is a figure which shows a mode that it consists of the soft-magnetic film | membrane 32a and the non-magnetic film | membrane 32b of one layer.

  In FIG. 3, the composite magnetic head is disposed so as to face the paper surface (corresponding to the magnetic recording medium surface), and the moving direction of the magnetic recording medium is the direction indicated by the arrow X. The direction perpendicular to the paper surface is the height direction.

Referring to FIG. 3, the composite magnetic head 20 is formed on a flat ceramic substrate or the like made of Al ₂ O ₃ —TiC (AlTiC) or the like serving as a base of the head slider (on the ceramic substrate 21 in this example). The magnetoresistive effect element 22 is formed on the alumina film 26, and the inductive magnetic recording element 23 is formed thereon.

  The inductive magnetic recording element 23 is opposed to the upper magnetic pole 24A across the upper magnetic pole 24A having a width L corresponding to the track width of the magnetic recording medium and the recording gap layer 25 made of a non-magnetic material. The lower magnetic pole 24B, a yoke (not shown) that magnetically connects the upper magnetic pole 24A and the lower magnetic pole 24B, a coil (not shown) that winds the yoke and induces a magnetic field by a recording current, and the like. The upper magnetic pole 24A, the lower magnetic pole 24B and the yoke are made of a soft magnetic material, and are made of a material having a high saturation magnetic flux density, such as Ni80Fe20, CoZrNb, FeN, FeSiN, FeCo alloy, etc. in order to secure a recording magnetic field.

  The magnetoresistive effect element 22 has a configuration in which a lower electromagnetic shield layer 28, a magnetoresistive effect film 1, an alumina film 31, and an upper electromagnetic shield layer 32 are sequentially laminated on an alumina film 26 formed on the surface of the ceramic substrate 21. The lower electromagnetic shield layer 28, the magnetoresistive effect film 1, and the upper electromagnetic shield layer 32 are electrically connected. Magnetic domain control films 34 are formed on both sides of the magnetoresistive effect film 1 via insulating films 33 having a thickness of about 10 nm or less. The magnetic domain control film 34 is made of, for example, a laminated film of Cr / CoCrPt, and is a film for preventing the occurrence of Barkhausen noise by making the magnetization fixed layer and the magnetization free layer constituting the magnetoresistive effect film 1 into a single domain. It is.

  The sense current Is for detecting the resistance change flows, for example, from the upper electromagnetic shield layer 32 to the lower electromagnetic shield layer 28 through the magnetoresistive effect film 1 and changes in response to the leakage magnetic field from the magnetic recording medium. Information recorded on the magnetic recording medium is reproduced by detecting the magnetic resistance as a signal voltage. The lower electromagnetic shield layer 28 and the upper electromagnetic shield layer 32 have both a function as a sense current flow path and an electromagnetic shield function. The magnetoresistive element 22 and the induction type magnetic recording element 23 are covered with an alumina film, a hydrogenated carbon film, or the like in order to prevent corrosion or the like.

  Next, an example of the magnetoresistive film according to the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view of an example of the magnetoresistive film 1 constituting the magnetoresistive element 22 in FIG. In this example, the magnetoresistive film is a single spin having a CPP structure in which a magnetization fixed layer 6, a nonmagnetic intermediate layer 7, a magnetization free layer 8 and a protective layer are sequentially laminated on an underlayer (not shown). It has a valve structure.

  The underlayer is formed by sputtering or the like on the surface of the lower electromagnetic shield 28 shown in FIG. The underlayer is made of NiCr, NiFeCr, Ta / NiFe, Ru or the like, and generally has a thickness of 4 nm or more.

  The magnetization fixed layer 6 according to the present invention needs to have a ferromagnetic film whose magnetization direction is substantially fixed in one direction. “Substantially” means that the magnetization pinned layer whose magnetization direction is fixed in one direction does not have to be a single film, and even when it is composed of a plurality of films, 3, the magnetization fixed layer 6 has an antiferromagnetic layer 2, a first ferromagnetic layer 3, a nonmagnetic coupling layer 4, It is comprised from the laminated body formed in order of the 2nd ferromagnetic layer 5. FIG.

  The antiferromagnetic layer can be made of IrMn, PtMn, PdPtMn, etc., and its thickness is generally 4 nm or more. The first ferromagnetic layer 3 and the second ferromagnetic layer 5 are antiferromagnetically exchange-coupled via the nonmagnetic coupling layer 4.

  Both the first ferromagnetic layer 3 and the second ferromagnetic layer 5 according to the present invention are made of a soft magnetic material, and are made of Co, Fe, Ni having a film thickness of 1 to 30 nm and an alloy containing these elements. can do. For example, FeCo, NiFe (permalloy), FeCoCu, etc. can be exemplified. Further, depending on the case, other elements may be added as long as ferromagnetism is not lost. As additive elements, B, C, N, O, F, Sc, Ti, V, Cr, Mn, Zn, Ga, Ge, As, Se, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd , Ag, Cd, In, Sn, Sb, Te, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, or At. Each of the first and second ferromagnetic layers may be a laminate of not only one layer but also two or more layers.

  The non-magnetic coupling layer according to the present invention comprises Ru, Rh, Ir, Ru-based alloy, Rh-based alloy, Ir-based alloy having a film thickness in the range of 0.4 nm to 1.5 nm (preferably 0.4 nm to 0.9 nm). It can comprise from nonmagnetic materials, such as. As the Ru-based alloy, an alloy obtained by adding any one of Co, Cr, Fe, Ni, and Mn to Ru is preferable.

  The nonmagnetic intermediate layer according to the present invention is made of a conductive material having a film thickness of 1.5 nm to 10 nm formed by, for example, sputtering, and is made of, for example, a Cu film, an Al film, or the like.

  The magnetization free layer according to the present invention comprises a ferromagnetic film whose magnetization direction changes according to an external magnetic field. This magnetization free layer is formed on the surface of the nonmagnetic intermediate layer by sputtering or the like, and has a film thickness of 1 nm to 30 nm of Co, Fe, Ni and a ferromagnetic material composed of these elements, for example, NiFe (Permalloy), FeCo, FeCoB or the like, or a laminated body of these films. The magnetization of the magnetization free layer faces in the in-plane direction, and the magnetization direction changes according to the direction of the magnetic field leaking from the magnetic recording medium. As a result, the resistance value of the layered structure of the magnetization fixed layer / nonmagnetic intermediate layer / magnetization free layer changes in accordance with the angle between the magnetization of the magnetization free layer and the magnetization of the magnetization fixed layer.

  The magnetization free layer may have a laminated structure. FIG. 4 is an enlarged view of a main part of such an example of the magnetization free layer. Referring to FIG. 4, in this example, the magnetization free layer 47 provided on the nonmagnetic intermediate layer 46 has a so-called laminated magnetization free layer structure composed of repetition of the ferromagnetic layer 47a / nonmagnetic conductive layer 47b. A protective layer 48 is provided thereon. The laminated magnetization free layer structure shown in FIG. 4 shows two repetitions of the ferromagnetic layer 47a / nonmagnetic conductive layer 47b, and the surface and bottom layers of the magnetization free layer 47 are the ferromagnetic layers 47a. The ferromagnetic layer 47a can be made of the same material as the magnetization free layer, and the nonmagnetic conductive layer 47b can be made of the same material (preferably Cu) as the nonmagnetic intermediate layer. Thus, by making the magnetization free layer have a laminated magnetization free layer structure, the coercive force of the magnetization free layer can be reduced to improve the magnetic field sensitivity and to improve the magnetoresistance change rate.

  In the laminated magnetization free layer structure, the repetition of the ferromagnetic layer 47a / nonmagnetic conductive layer 47b is preferably in the range of 2 to 3 times, and the thickness of the ferromagnetic layer 47a is preferably set in the range of 1 nm to 2 nm. The film thickness of the nonmagnetic conductive layer 47b is preferably set in the range of 0.3 nm to 2 nm. Further, the ferromagnetic layers 47a may be a laminate of ferromagnetic layers having different compositions.

  The protective layer according to the present invention is formed on the surface of the magnetization free layer by sputtering or the like, and may be composed of, for example, a conductive film made of Ru, Cu, Ta, Au, Al, W, or a laminate thereof. it can. In this way, it is possible to prevent the magnetoresistive film 1 from being oxidized during the heat treatment or the like. In addition, by using a Cu film as the protective layer, the resistance change rate can be improved by forming a magnetic / nonmagnetic interface with the magnetization free layer.

  Since the electromagnetic shield layer according to the present invention has a three-layer structure, the direction of magnetization of the electromagnetic shield layer becomes antiparallel due to the current magnetic field. Considering the influence of the magnetic field from the magnetic domain control film 34, a current is passed as shown in FIG. 1, and the magnetization direction of the electromagnetic shield adjacent to the magnetoresistive effect element film is set to the magnetization of the magnetic domain control film determined at the time of magnetization. The flow should match the direction. In this way, as shown in FIG. 1, if the direction of magnetization of the electromagnetic shield layer is antiparallel, the current magnetic field in the in-layer direction of the electromagnetic shield layer can be made uniform. Thus, in the electromagnetic shield layer, the generation of local magnetic domains that degrade the performance of the magnetoresistive effect film can be suppressed, and the leakage magnetic field leaking from the electromagnetic shield layer to the magnetoresistive effect film side can be suppressed.

  In general, the electromagnetic shield layer according to the present invention has a thickness of the lower electromagnetic shield layer of about 10 μm and a thickness of the lower electromagnetic shield layer of several tens of μm, but may have other thicknesses. . For example, the thickness of one electromagnetic shield layer can be about 1 μm.

  At least one of the four soft magnetic films forming the electromagnetic shield layer according to the present invention can be made of a general soft magnetic material. For example, it can be composed of an alloy containing an element such as Co, Fe, or Ni. More specifically, NiFe (permalloy) and CoNbZr can be exemplified. Further, depending on the case, other elements may be added as long as ferromagnetism is not lost. As additive elements, B, C, N, O, F, Sc, Ti, V, Cr, Mn, Zn, Ga, Ge, As, Se, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd , Ag, Cd, In, Sn, Sb, Te, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, or At. Further, a high resistance amorphous soft magnetic material may be used as the soft magnetic material. The high resistance amorphous soft magnetic material is more preferable in that the current concentrates more effectively on the nonmagnetic film and a high current magnetic field can be obtained. An example is FeCuNbSiB.

  The material of the nonmagnetic film according to the present invention is not particularly limited, and a known material can be used, but Au, Ag, or Cu is preferable for the reason described later. However, the case where all of the nonmagnetic films according to the present invention are not Au, Ag, or Cu is included.

  When the electromagnetic shield layer according to the present invention is used, the current magnetic field is used to make the current magnetic field in the in-layer direction uniform in the electromagnetic shield layer, thereby reducing the performance of the magnetoresistive film in the electromagnetic shield layer. In order to ideally suppress the generation of local magnetic domains, it has been found that it is important to change the film thickness according to the specific resistance ratio of the soft magnetic film and the nonmagnetic film.

The reason is as follows. First, it is necessary to formulate a current magnetic field generated inside the electromagnetic shield layer. In order to easily derive the current magnetic field, the soft magnetic film 28A / nonmagnetic film 28B / soft magnetic film 28A shown in FIG. 5 (similar to the electromagnetic shield layer represented by reference numeral 28 or 32 in FIG. 1B) 3 × 99 square lattices (black circles) in the center of the thickness of each of the soft magnetic film 28A / nonmagnetic film 28B / soft magnetic film 28A. The current magnetic field at the center point A corresponding to the center portion of the magnetoresistive film is derived. Here, the current flowing through each lattice of the non-magnetic film and the soft magnetic film is represented by i _c , i _sh , the specific resistance of the non-magnetic film and the soft magnetic film, respectively, ρ _c , ρ _sh , and the electromagnetic shield layer. The thickness is L _sh , and the ratio of the nonmagnetic film to the electromagnetic shield layer thickness is x (therefore, the thickness of the nonmagnetic film is xL _sh ). The current magnetic field generated at the central point A when defined in this way is described as follows.

ここで、r_i：格子点iからA点までのベクトル、i_i：格子点iを流れる電流ベクトル（i_iの大きさは、格子点が軟磁性膜部分、非磁性膜部分に有る場合で、それぞれi_sh、i_cで与えられる）とする。

Here, r _i : vector from lattice point i to point A, i _i : current vector flowing through lattice point i (i _{i is} the magnitude when the lattice point is in the soft magnetic film part and the non-magnetic film part. , Given by i _sh and i _c , respectively).

The calculation results are shown below. Here, H _x represents a magnetic field in a direction perpendicular to the film surface of the electromagnetic shield layer, and H _y represents a magnetic field in an in-plane direction of the electromagnetic shield layer.

この計算結果より、電磁シールド層の膜面に直交する方向への磁界Ｈ_ｘが０であることがわかる。

From this calculation result, it can be seen that the magnetic field H _{x in the} direction orthogonal to the film surface of the electromagnetic shield layer is zero.

As the sense current Is, the sum of the currents i _c and i _sh flowing through the lattice points becomes the sense current Is.
_{99i c} + 198i sh = Is
It becomes.

  In addition, each grid forms a parallel circuit, and the voltage applied to each grid is the same, so the following equation holds.

以上の式を使用すれば、いかなる非磁性膜、軟磁性膜材料の組み合わせでも、電流磁界（すなわち、電磁シールド層の面内方向への磁界Ｈ_ｙ）を最大とする最適膜厚が導出できる。Ｈｙを最大にする膜厚の関係であれば、その電流磁界により電磁シールド層における層内方向の電流磁界を最大限に一様にし、これにより、電磁シールド層において、磁気抵抗効果膜の性能を低下させるローカルな磁区の発生を最大限に抑えていると考えることができる。

If the above formula is used, the optimum film thickness that maximizes the current magnetic field (that is, the magnetic field H _y in the in-plane direction of the electromagnetic shield layer) can be derived for any combination of non-magnetic film and soft magnetic film materials. If the film thickness relationship maximizes Hy, the current magnetic field makes the current magnetic field in the in-layer direction uniform in the electromagnetic shield layer to the maximum, thereby improving the performance of the magnetoresistive effect film in the electromagnetic shield layer. It can be considered that generation of local magnetic domains to be reduced is suppressed to the maximum.

  A magnetoresistive element having such a three-layered electromagnetic shield layer can be suitably used for a magnetic head of a magnetic recording apparatus for recording or reproducing magnetic information. FIG. 6 is a diagram showing a main part of a magnetic recording apparatus using the magnetoresistive effect element according to the present invention. Referring to FIG. 6, a magnetic recording apparatus 90 includes a housing 92, a hub 92 driven by a spindle (not shown), a magnetic recording medium 93 fixed to the hub 92 and rotated, an actuator unit 94, and an actuator unit. 94, an arm 95 and a suspension 96 that are movable in the radial direction of the magnetic recording medium 93, and a magnetic head 20 supported by the suspension 96 are provided. By constructing the magnetic head 20 from the magnetoresistive effect element 22 as shown in FIGS. 1A and 1B and the inductive magnetic recording element 23 formed thereon, a magnetic recording apparatus having high resolution can be obtained. It is done.

  The magnetic recording medium used in the present invention is not limited to a magnetic disk as long as it is a perpendicular magnetic recording system, and may be a magnetic tape.

  Next, examples of the present invention will be described in detail.

  FIG. 7 shows a case where NiFe is used as the material of the soft magnetic film and Cu is selected as the material of the nonmagnetic film when the total film thickness of one electromagnetic shield layer is 1 μm and the sense current Is is 7 mA. The change of the current magnetic field with respect to the ratio x of the nonmagnetic film to the electromagnetic shield film thickness (left vertical axis) and the ratio of current concentration on the nonmagnetic film (right vertical axis) were obtained using the above formula. Results are shown.

  From this result, the maximum of the current magnetic field (Hy in FIG. 5) is 1.65 Oe, the current concentration ratio at that time is 75.4%, and the ratio x of the nonmagnetic film to the electromagnetic shield thickness is 16%. Is understood. That is, when NiFe is used as the material of the soft magnetic film and Cu is selected as the material of the nonmagnetic film, the ratio x of the nonmagnetic film to the film thickness of the electromagnetic shield layer is set to 16%. It can be seen that the magnetic field can be maximized to 1.65 Oe and the rate of current concentration on the nonmagnetic film can be increased to 75.4%.

  Such a current magnetic field does not interfere with the function of the electromagnetic shield layer that absorbs the signal magnetic field from adjacent bits. Therefore, the larger the current magnetic field, the more the performance of the magnetoresistive film in the electromagnetic shield layer. This is preferable because it is easy to suppress the generation of local magnetic domains to be lowered. Current concentration on the nonmagnetic film is generally preferable because the film thickness of the nonmagnetic film can be reduced.

  Table 1 summarizes this calculation for various soft magnetic materials and non-magnetic materials. Table 1 shows the case where NiFe, CoNbZr, FeCuNbSiB is selected as the soft magnetic material, Au, Ag, Cu is selected as the material of the nonmagnetic film, the thickness of the electromagnetic shield layer is 1 μm, and the sense current is 7 mA. The calculation results of the ratio of the nonmagnetic film thickness and the ratio of current concentration in the total electromagnetic shield film thickness when the current magnetic field is maximized are shown for these combinations.

この表より得られた、様々な材料の組み合わせについて、変化する軟磁性膜と非磁性膜の比抵抗の比に対する、最大電流磁界、一つの電磁シールド層全体の膜厚に占める非磁性膜の膜厚の割合および非磁性膜への電流集中の割合の関係を図８に示す。図８より、軟磁性膜の比抵抗対非磁性膜の比抵抗の比が大きくなるにつれ、電流磁界の大きさを大きくでき、また、非磁性膜の膜厚の電磁シールド層の総膜厚に占める割合を低下でき、電磁シールド層の総膜厚の０．２％程度で、電流集中の割合が９９％、電流磁界の大きさが２．２Ｏｅ程度まで増加することが理解される。

For the combination of various materials obtained from this table, the maximum current magnetic field to the ratio of the specific resistance of the soft magnetic film to the nonmagnetic film, the film of the nonmagnetic film occupying the entire film thickness of one electromagnetic shield layer FIG. 8 shows the relationship between the ratio of thickness and the ratio of current concentration on the nonmagnetic film. From FIG. 8, as the ratio of the specific resistance of the soft magnetic film to the specific resistance of the nonmagnetic film increases, the magnitude of the current magnetic field can be increased, and the total thickness of the electromagnetic shield layer can be increased to the nonmagnetic film thickness. It can be understood that the ratio can be reduced, the ratio of current concentration increases to 99%, and the magnitude of the current magnetic field increases to about 2.2 Oe at about 0.2% of the total film thickness of the electromagnetic shield layer.

  From these results, the following can be said for the specific resistance, film thickness, material, etc. of the soft magnetic film and the nonmagnetic film.

  That is, it is preferable to use a high resistance material for the specific resistance of the soft magnetic film constituting the electromagnetic shield layer. For example, the specific resistances of NiFe, CoZrNb, and FeCuNbSiB are about ˜25, ˜200, and ˜100,000 μΩcm, respectively. Therefore, it can be said that the specific value of the specific resistance is preferably 25 μΩcm or more.

  The specific resistance of the nonmagnetic film is preferably as low as possible. Specifically, Au, Cu and Ag are preferable. Therefore, it can be said from the results with these materials that the specific resistance of the specific nonmagnetic film is preferably 2.1 μΩcm or less.

  The above condition does not necessarily have to be satisfied for all of the soft magnetic film and the non-magnetic film, and may be satisfied for at least one of them.

  It can be said that the thickness of one layer of the nonmagnetic film is preferably 20% or less of the total film thickness of the electromagnetic shield layer including the nonmagnetic film. A range of 0.2 to 20% is practical and more preferable. Accordingly, the film thickness of one layer of the soft magnetic film is preferably 40% or more of the entire film thickness of the electromagnetic shielding layer including the soft magnetic film, and more preferably in the range of 40 to 49.9%. It can be said.

  In addition, the invention shown to the following additional remarks can be derived from the content disclosed above.

(Appendix 1)
A lower electromagnetic shield layer and an upper electromagnetic shield layer that function as an electrode and an electromagnetic shield, and a magnetoresistive film sandwiched between the two electromagnetic shield layers, and perpendicular to the film surface of the magnetoresistive film A magnetoresistive effect element capable of energizing a magnetic field, wherein at least one electromagnetic shield layer is formed of three layers of a soft magnetic film / nonmagnetic film / soft magnetic film.

(Appendix 2)
The magnetoresistive effect element according to appendix 1, wherein the two electromagnetic shield layers are each formed of three layers of a soft magnetic film / a nonmagnetic film / a soft magnetic film.

(Appendix 3)
The magnetoresistive film includes a magnetization fixed layer having a ferromagnetic film whose magnetization direction is substantially fixed in one direction, a nonmagnetic intermediate layer, and a ferromagnetic material whose magnetization direction changes according to an external magnetic field. The magnetoresistive effect element according to appendix 1 or 2, which includes a magnetization free layer made of a film and is capable of energizing in a direction perpendicular to the film surfaces of these layers.

(Appendix 4)
The magnetoresistive effect element according to any one of appendices 1 to 3, wherein at least one of the soft magnetic films is made of a soft magnetic material which may be a high-resistance amorphous soft magnetic material.

(Appendix 5)
The magnetoresistive effect element according to appendix 4, wherein the soft magnetic material is NiFe or CoNbZr.

(Appendix 6)
The magnetoresistive element according to appendix 4 or 5, wherein the high-resistance amorphous soft magnetic material is FeCuNbSiB.

(Appendix 7)
The magnetoresistive element according to any one of appendices 1 to 5, wherein the specific resistance of at least one of the soft magnetic films is 25 μΩcm or more.

(Appendix 8)
The magnetoresistive effect element according to any one of appendices 1 to 7, wherein the thickness of one layer of the soft magnetic film is 40% or more of the total film thickness of the electromagnetic shield layer including the soft magnetic film.

(Appendix 9)
The magnetoresistive element according to any one of appendices 1 to 8, wherein the specific resistance of at least one of the nonmagnetic films is 2.1 μΩcm or less.

(Appendix 10)
The magnetoresistive element according to appendix 9, wherein at least one of the nonmagnetic films is made of Au, Ag, or Cu.

(Appendix 11)
The magnetoresistive effect element according to any one of appendices 1 to 10, wherein a thickness of one layer of the nonmagnetic film is 20% or less of a total thickness of the electromagnetic shield layer including the nonmagnetic film.

(Appendix 12)
A magnetic head comprising the magnetoresistive element according to any one of appendices 1 to 11.

(Appendix 13)
A magnetic recording apparatus comprising the magnetic head according to appendix 12.

It is a typical perspective view of the structure of the electromagnetic shielding layer which concerns on this invention. It is the figure which looked at the electromagnetic shielding layer of Drawing 1-A from the ABS side. It is sectional drawing of an example of a magnetoresistive effect film. It is a figure which shows the structural example of a composite type magnetic head. It is a principal part enlarged view of a magnetization free layer. It is a schematic diagram of the electromagnetic shielding layer for electric current magnetic field derivation | leading-out. It is a figure which shows the principal part of the magnetic-recording apparatus using the magnetoresistive effect element based on this invention. It is a graph which shows the ratio of the current magnetic field and current concentration when NiFe is used as the material of the soft magnetic film and Cu is selected as the material of the nonmagnetic film. It is a graph which shows (a) the maximum current magnetic field, (b) the ratio of the nonmagnetic film in the electromagnetic shield layer, and (c) the ratio of current concentration with respect to the specific resistance ratio of the soft magnetic material and the nonmagnetic material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetoresistance effect film | membrane 2 Antiferromagnetic layer 3 1st ferromagnetic layer 4 Nonmagnetic coupling layer 5 2nd ferromagnetic layer 6 Magnetization fixed layer 7 Nonmagnetic intermediate | middle layer 8 Magnetization free layer 20 Composite type magnetic head 21 Substrate 22 Magnetoresistive element 23 Inductive magnetic recording element 24A Upper magnetic pole 24B Lower magnetic pole 25 Recording gap layer 26 Alumina film 28 Lower electromagnetic shield layer 28A Soft magnetic film 28B Nonmagnetic film 31 Alumina film 32 Upper electromagnetic shield layer 32A Soft magnetic film 32B Non Magnetic film 33 Insulating film 34 Magnetic domain control film 46 Nonmagnetic intermediate layer 47 Magnetization free layer 48 Protective layer 90 Magnetic recording device 91 Housing 92 Hub 93 Magnetic recording medium 94 Actuator unit 95 Arm 96 Suspension

Claims (5)

  A lower electromagnetic shield layer and an upper electromagnetic shield layer that function as an electrode and an electromagnetic shield, and a magnetoresistive film sandwiched between the two electromagnetic shield layers, and perpendicular to the film surface of the magnetoresistive film A magnetoresistive effect element capable of energizing a magnetic field, wherein at least one electromagnetic shield layer is formed of three layers of a soft magnetic film / nonmagnetic film / soft magnetic film.   The magnetoresistive film includes a magnetization fixed layer having a ferromagnetic film whose magnetization direction is substantially fixed in one direction, a nonmagnetic intermediate layer, and a ferromagnetic material whose magnetization direction changes according to an external magnetic field. The magnetoresistive effect element according to claim 1, further comprising a magnetization free layer made of a film and capable of being energized in a direction perpendicular to the film surfaces of these layers.   The magnetoresistive effect element according to claim 1 or 2, wherein at least one of the soft magnetic films is made of a soft magnetic material which may be a high-resistance amorphous soft magnetic material.   A magnetic head comprising the magnetoresistive effect element according to claim 1.   A magnetic recording apparatus comprising the magnetic head according to claim 4.

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