JP2002299723A - Magnetoresistance effect element and thin-film magnetic head using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of a magnetoresistance effect element of synthetic ferri-free(SFF)structure not appropriately matching with a hard bias layer and a stabilized anti-parallelism can be realized, without generating disturbance of magnetization direction adjacent to the edge of a free magnetic layer, which results in lowering of reliability. SOLUTION: A free magnetic layer 25, formed in a multi-layer film 20, has a synthetic ferri-free(SFF) structure which has three layers, a first free magnetic layer 25A, an intermediate layer 25B and a second free magnetic layer 25C; and the intermediate layer 25B is made of Ru, and at least either of the first free magnetic layer 25A and second free magnetic layer 25C is made of CoFeNi alloy, where the composition ratio of the CoFeNi alloy shows Fe of 9 atm.% or more and 17 atom.% or less, Ni of 0.5 atom.% or more and 10 atm.% or less, and the remaining part being made of Co.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive element in which electric resistance changes according to a relation between a fixed magnetization direction of a fixed magnetic layer and a magnetization direction of a free magnetic layer affected by an external magnetic field, and more particularly to a free magnetic layer. A magnetoresistive element capable of dividing the layer into two layers and keeping the magnetization (ferri state) of the two magnetic layers stable against a hard bias magnetic field, and a thin film magnetic element using the magnetoresistive element About the head.

[0002]

2. Description of the Related Art FIG. 8 is a sectional view showing a structure of a conventional spin-valve type thin film element when viewed from a surface (ABS surface) facing a recording medium. In this spin-valve thin film element, an antiferromagnetic layer 102 is formed on a base layer 101 made of Ta (tantalum) or the like, and a fixed magnetic layer 103 is formed on the antiferromagnetic layer 102. ing. The fixed magnetic layer 103 includes the antiferromagnetic layer 10
2, an exchange coupling magnetic field (exchange anisotropic magnetic field) is generated at the interface between the fixed magnetic layer 103 and the antiferromagnetic layer 102, and the magnetization of the fixed magnetic layer 103 is, for example, Y in FIG. Fixed in the direction.

A nonmagnetic conductive layer 104 made of Cu or the like is formed on the fixed magnetic layer 103, and a free magnetic layer 105 is formed on the nonmagnetic conductive layer 104. On both sides of the free magnetic layer 105, for example, C
The hard bias layer 106 made of an o-Pt alloy is formed, and the hard bias layer 106 is magnetized in the illustrated X direction, so that the magnetization of the free magnetic layer 105 is aligned in the illustrated X direction. . Thus, the variable magnetization of the free magnetic layer 105 and the fixed magnetization of the fixed magnetic layer 103 cross each other. Incidentally, reference numeral 108 in FIG.
Is a conductive layer formed of Cu or the like, and 109 is a protective layer.

In this spin-valve type thin-film element, when the magnetization of the free magnetic layer 105 aligned in the X direction shown in the figure fluctuates due to a leakage magnetic field from a recording medium such as a hard disk (not shown), the fixed pinned in the Y direction shown in the figure. Magnetic layer 10
The electric resistance changes in relation to the fixed magnetization of No. 3, and a leakage magnetic field from the recording medium is detected by a voltage change based on the change in the electric resistance value.

By the way, in order to improve the reproduction sensitivity and the like, it has been studied to reduce the thickness of the free magnetic layer 105. However, there is a restriction in reducing the thickness in this way, and the thickness cannot be reduced without limitation. When the thickness of the free magnetic layer 105 is reduced, the rate of change in resistance (ΔR
/ R) and the change in resistance (ΔR) are degraded, and the soft magnetic characteristics of the free magnetic layer 105 are degraded. In particular, the present inventors have found that the magnetoresistance ratio (ΔR / R) becomes maximum when the thickness of the free magnetic layer is around 3 nm.

Therefore, as shown in FIG. 9, in order to improve the resistance change rate (ΔR / R) and the resistance change (ΔR) when the effective free magnetic layer is thin, a plurality of free magnetic layers 105 are provided. Various types of laminated ferri-free type (synthetic ferri-free (hereinafter, referred to as SFF)) magnetoresistive elements including layers have been proposed. In this SFF, the magnetizations of the first free magnetic layer 105A and the second free magnetic layer 105C are
They are connected so as to be antiparallel via the intermediate layer 105B. Here, the first and second free magnetic layers 105A, 105A
The difference between the saturation magnetization and the film thickness of 5C is the effective magnetization of the free magnetic layer.
[(Film thickness) × (saturation magnetization)]. Therefore, the first and second
By reducing the thickness difference between the free magnetic layers 105A and 105C, the effective free magnetic layer thickness can be reduced without increasing the physical free magnetic layer thickness, thereby improving the read sensitivity. As a result, excellent characteristics such as ΔR / R, ΔR, and little deterioration of the soft magnetic characteristics of the free layer can be obtained.

However, the magnetoresistive effect element having the SFF is not compatible with the hard bias layer and has not been put to practical use. For example, the composition of each of the first free magnetic layer (hereinafter, referred to as F1 layer) 105A / intermediate layer 105B / second free magnetic layer (hereinafter, referred to as F2 layer) 105C is NiFe / Ru / NiFe. A resistance effect element has been proposed. However, in this configuration, the material of the F1 layer 105A and the F2 layer 105C in contact with Ru of the intermediate layer 105B is NiFe,
Since the anti-parallel coupling force between the two layers is relatively weak, the so-called “spin flop magnetic field” where the anti-parallel state starts to collapse is relatively small.

Further, in this configuration, since the hard bias magnetic field near the track edge is strong, as shown in FIG. 10, the F1 layer 1 facing in the direction opposite to the hard bias magnetic field direction.
05A causes frustration with the hard bias magnetic field near the track edge, and the F1 layer 10
The magnetization distribution of 5A is disturbed. As a result, the magnetization of the track edge of the F2 layer 105C that contributes to the reproduction is also disturbed, causing distortion and instability in the reproduction waveform and the track profile.

Accordingly, the present invention has been made in view of the above-mentioned circumstances,
Stacked ferri-free type (even with a synthetic ferri-free structure, it is possible to realize a stable anti-parallel state without generating disturbance in the magnetization direction near the edge of the free magnetic layer in the track width direction, It is another object of the present invention to provide a magnetoresistive element having high reliability in reproducing characteristics and a thin-film magnetic head having high reproducing sensitivity using the magnetoresistive element.

[0010]

SUMMARY OF THE INVENTION The present invention provides a multilayer film exhibiting a magnetoresistive effect, hard bias layers provided on both sides of the multilayer film in the track width direction, and an electrode layer laminated on the hard bias layer. Wherein the free magnetic layer provided in the multilayer film has a synthetic ferri-free (SFF) structure having three layers of a first magnetic layer / non-magnetic intermediate layer / second magnetic layer. The non-magnetic intermediate layer is made of Ru; at least one of the first magnetic layer and the second magnetic layer is made of a CoFeNi alloy;
The composition ratio of the i-alloy is as follows: Fe is at least 9 at.% and at most 17 at.
o.

The multilayer film is formed in contact with the antiferromagnetic layer, and a fixed magnetic layer whose magnetization direction is fixed by an exchange anisotropic magnetic field with the antiferromagnetic layer; A nonmagnetic conductive layer formed between the pinned magnetic layer and the free magnetic layer, wherein the second magnetic layer is disposed between the nonmagnetic conductive layer and the nonmagnetic intermediate layer; The second magnetic layer may be formed of the CoFeNi alloy.

Further, the multilayer film is formed in contact with the antiferromagnetic layer and the antiferromagnetic layer, and the magnetization direction is fixed by an exchange anisotropic magnetic field with the antiferromagnetic layer. And a nonmagnetic conductive layer formed between the fixed magnetic layer and the free magnetic layer, wherein the second magnetic layer is disposed between the nonmagnetic conductive layer and the nonmagnetic intermediate layer, The two magnetic layers may be formed of a CoFeNi alloy, and the first magnetic layer may be formed of a CoFe alloy.

Further, the present invention provides an antiferromagnetic layer, a fixed magnetic layer formed in contact with the antiferromagnetic layer and having a magnetization direction fixed by exchange anisotropy with the antiferromagnetic layer. Having a free magnetic layer formed with a non-magnetic conductive layer interposed therebetween,
A magnetoresistive element having a multilayer film exhibiting a magnetoresistive effect, hard bias layers provided on both sides of the multilayer film, and an electrode layer laminated on the hard bias layer, wherein the multilayer film Has a synthetic ferri-free (SFF) structure having three layers of a first magnetic layer / a non-magnetic intermediate layer / a second magnetic layer, and the second magnetic layer is formed of a non-magnetic conductive layer and a non-magnetic conductive layer. Disposed between the non-magnetic intermediate layer,
A magnetic layer made of a CoFe alloy is formed between the second magnetic layer and the nonmagnetic conductive layer; the nonmagnetic intermediate layer is made of Ru; the second magnetic layer is made of CoFeNi;
The composition ratio of the oFeNi alloy is such that Fe is at least 7 at% and at most 15 at%, Ni is at least 5 at% and at most 15 at%, and the balance is Co.

The track width of the free magnetic layer is 0.4
μm or less, and the thickness of the hard bias layer is 20 nm.
To 50 nm.

The track width of the free magnetic layer is 0.3
μm or less, and the thickness of the hard bias layer is 13 nm.
To 40 nm.

The track width of the free magnetic layer is 0.2
μm or less, and the thickness of the hard bias layer is 10 nm.
To 35 nm.

The magnetoresistive element of the present invention may be a bottom-type spin-valve thin-film element in which the multilayer film includes, in order from the bottom, an antiferromagnetic layer, a fixed magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer. .

The magnetoresistive element of the present invention may be a top-type spin-valve thin-film element in which the multilayer film includes, in order from the bottom, a free magnetic layer, a nonmagnetic conductive layer, a fixed magnetic layer, and an antiferromagnetic layer. .

In the magnetoresistive element according to the present invention, the multilayer film includes a free magnetic layer, a non-magnetic conductive layer formed above and below the free magnetic layer, and a non-magnetic conductive layer on one non-magnetic conductive layer and the other. A configuration including a fixed magnetic layer formed below the magnetic conductive layer and having a fixed magnetization direction, and an antiferromagnetic layer formed above one fixed magnetic layer and below the other fixed magnetic layer may be employed. .

Preferably, a seed layer is formed under the antiferromagnetic layer or under the free magnetic layer.

Further, a thin-film magnetic head according to the present invention is provided with the above-mentioned magnetoresistive effect element.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a spin-valve thin film element 2 which is one of the magnetoresistive elements according to the present invention, as viewed from a recording medium facing surface (ABS surface) side. FIG. FIG. A shield layer is formed above and below the spin-valve thin-film element 2 via a gap layer (not shown). The spin-valve thin-film element 2, the gap layer, and the shield layer are used for reproducing a thin-film magnetic head (MR). Head). In addition, above the thin-film magnetic head for reproduction (Z direction),
Inductive heads for recording may be stacked.

This thin-film magnetic head is provided at the trailing end of a floating slider provided on a hard disk device (not shown), and is provided on a magnetic recording medium such as a hard disk (not shown). Detect information. The moving direction of the magnetic recording medium such as a hard disk is the Z direction, and the direction of the leakage magnetic field from the magnetic recording medium is the Y direction.

The spin-valve thin film element 2 shown in FIGS. 1 and 2 has a so-called single-spin structure in which an antiferromagnetic layer 22, a fixed magnetic layer 23, a nonmagnetic conductive layer 24 and a free magnetic layer 25 are formed one by one. A valve-type thin film element,
The substrate 11 is located at the lowest position. The substrate 11 is formed of a ceramic material such as alumina titanium carbide (Al ₂ 0 ₃ -TiC). On this substrate 11, a shield layer 12 is formed.

The lower shield layer 12 is provided on the lower side of the spin-valve type thin film element 2 to provide a magnetic shield for a magnetic field other than a recording bit on a medium to be reproduced, and is formed of a magnetic material. Is done.

Further, a lower gap layer 13 is formed above the lower shield layer 12. The lower gap layer 13 is for ensuring electrical insulation between the spin valve thin film and the electrode layer 34 described below and the lower shield layer 12, and includes alumina (Al ₂ O ₃ ),
Such as SiO _2, Al-SiO is used as a material.

The antiferromagnetic layer 22, the pinned magnetic layer 23, and the nonmagnetic conductive layer 2 are located immediately above the upper surface (the surface on which the spin-valve thin film element is formed) of the central portion of the lower gap layer 13.
4. The spin-valve thin film element 2 in which the free magnetic layer 25 and the like are stacked is formed. In this embodiment,
To prevent diffusion, a diffusion prevention film made of CoFe or Co
Although it is not interposed between the nonmagnetic conductive layer 24 and the free magnetic layer 25, it may be interposed. This diffusion prevention film functions as a part of a second free magnetic layer described later. The width dimension (Tw) of the upper surface 20a of the spin-valve thin film element 2 constitutes a track width when optically measured.

This spin-valve thin film element 2 is shown in FIG.
2, an antiferromagnetic layer 22 is formed on the seed layer layer 21, a first fixed magnetic layer 23A is formed on the antiferromagnetic layer 22, and the first fixed magnetic layer 23A is formed on the antiferromagnetic layer 22. 23
A, a non-magnetic intermediate layer 23B is formed on A, and a second fixed magnetic layer 23C is formed on the non-magnetic intermediate layer 23B. The nonmagnetic conductive layer 24 is formed on the second pinned magnetic layer 23C. further,
On this nonmagnetic conductive layer 24, a second free magnetic layer 25
C is formed, a non-magnetic intermediate layer 25B is formed on the second free magnetic layer 25C, and a first free magnetic layer 25A is formed on the non-magnetic intermediate layer 25B. On the first free magnetic layer 25A, a protective layer 26 is formed of Ta (tantalum) or the like.

The seed layer 21 is composed of a base layer and an alignment layer formed of a non-magnetic material or a magnetic material laminated thereon. Note that this seed layer layer 21
May be composed of only one orientation layer formed of a nonmagnetic material or a magnetic material, but it is preferable that an underlayer is formed in order to adjust the crystal orientation of the orientation layer.
The underlayer has a function of preventing diffusion between the lower gap layer 13 and the spin-valve thin film element 2. On the other hand, the orientation layer has a small effect of preventing diffusion, but has an effect of improving the crystallinity and crystal orientation of the spin-valve thin film element.

The underlayer is made of Ta (tantalum), Hf (hafnium), Nb (niobium), Zr (zirconium),
It is preferable to be formed of at least one or more of i (titanium), Mo (molybdenum), and W (tungsten).

On the other hand, the alignment layer is formed of a magnetic material or a non-magnetic material as described above, but is preferably formed of a high resistance material. This alignment layer is made of, for example, NiFe.
Y alloy (Y is Cr, Rh, Ta, Hf, Nb,
Zr, Ti or at least one selected from Zr and Ti). Among them, the orientation layer is NiFeCr
More preferably, it is formed of an alloy.

If the orientation layer has a high specific resistance, the seed layer 2 of the sense current flowing from the electrode layer 34 described later is used.
It is possible to suppress the branch flow to 1. Thereby, the resistance change rate (ΔMR) can be improved, and the asymmetry of the reproduced waveform and Barkhausen noise can be reduced.

The antiferromagnetic layer 22 is preferably formed of a PtMn alloy. This PtMn alloy has conventionally been
NiMn alloy or Fn used as the antiferromagnetic layer 22
It is superior in corrosion resistance to eMn alloys and the like, has a high blocking temperature, and has a large exchange coupling magnetic field (exchange anisotropic magnetic field) at the interface with the fixed magnetic layer 23 described below.
Further, instead of the PtMn alloy, X-Mn (where X is
Any one of Pd, Ir, Rh, Ru, Os or 2
Alloy or Pt-Mn-X '
(Where X 'is Pd, Ir, Rh, Ru, Os, A
u or Ag is one or more elements)
It may be formed of an alloy. The antiferromagnetic layer 22 has a thickness of 8
It is preferable that the film is formed with a thickness of 0 ° or more and 300 ° or less.

The pinned magnetic layer 23 is composed of the first pinned magnetic layer 23
A, non-magnetic intermediate layer 23B and second pinned magnetic layer 23C
Synthetic Ferripind Layer (SFP)
, But may have a single-layer structure. The first pinned magnetic layer 23A and the second pinned magnetic layer 23C are made of, for example, a CoFe alloy.
It may be formed of an iFe alloy, a CoFe alloy, or the like. The nonmagnetic intermediate layer 23B is made of Ru, Ir, Rh, Cu,
It is formed of a material such as Cr.

The second free magnetic layer 25C includes CoFe
A Ni alloy is used with a limited composition, and Ru, Rh, Ir, Cu, Cr, or the like can be used as a material for the nonmagnetic intermediate layer 25B, but Ru is preferable. The second free magnetic layer 25C is a single layer or a CoFe / CoFeN layer in which CoFe is disposed as a diffusion preventing layer on the nonmagnetic conductive layer 24 side.
i may be a two-layer structure. First free magnetic layer 25A
Preferably uses a single layer of CoFeNi alloy,
An oFe single layer may be used.

In the track width direction (X direction), the bias underlayer 31, the hard bias layer 32, the intermediate layer 33, and the electrode layer 34 are arranged in order from the bottom on both sides of the track width Tw of the spin-valve thin film element 2. Are respectively laminated.

The bias underlayer 31 is preferably formed of a metal film having a body-centered cubic structure (bcc structure). In this case, the crystal orientation of the bias underlayer 31 is preferably such that the (200) plane is preferentially oriented. Specifically, it is preferably formed of one or more of Cr, W, Mo, and Ta elements.
It is preferable to form a film. This is because the Cr film has an excellent function of adjusting the crystal orientation of the hard bias layer 32, and can appropriately increase the coercive force and the squareness ratio of the hard bias layer 32.

Next, a hard bias layer 32 is formed on the bias underlayer 31. This hard bias layer 32 is formed of a hard magnetic material such as a CoPt alloy or a CoPtCr alloy.

Further, an electrode layer 34 is formed on the hard bias layer 32 via an intermediate layer 33. Note that a protective layer (not shown) is formed on the electrode layer 34. The intermediate layer 33 is made of Ta, Cr, W, or the like, and the electrode layer 34 is made of Au, Ta, Cr, Rh, W
Are commonly used. In addition, Ta is used for the protective layer.
Is used.

On the spin-valve thin film element 2 formed in this manner, an electrically insulating material such as alumina (Al ₂ O ₃ ), SiO ₂ , Al—Si—O, for example, which is the same as the lower gap layer 13, is formed. The upper gap layer is formed using the above material, and the upper shield layer is formed on the upper gap layer using a magnetic material.

Next, a characteristic configuration according to this embodiment will be described. First, regarding the fixed magnetic layer 23, the first
In the fixed magnetic layer 23A and the second fixed magnetic layer 23C,
A magnetic moment (magnetic thickness) M, whose size and direction is indicated by symbols and arrows in FIGS. 1 and 2, respectively, is acting. This magnetic moment per unit area (M)
Is defined as the product of the saturation magnetization (Ms) and the film thickness (t), that is, the following equation: M = Ms · t (1) It is what has been.

As described above, the first pinned magnetic layer 23A and the second pinned magnetic layer 23C are made of the same material, for example, Co.
Although it is formed of an Fe alloy, the second pinned magnetic layer 23C
Is larger than the film thickness tp of the first pinned magnetic layer 23A.
1, the second pinned magnetic layer 2
3C has a larger magnetic moment than the first pinned magnetic layer 23A. Note that the first pinned magnetic layer and the second pinned magnetic layer need to have magnetic moments of different magnitudes, so that the thickness of the first pinned magnetic layer is It may be formed thicker than the thickness of the fixed magnetic layer.

The first fixed magnetic layer 23A has a height (+
The second pinned magnetic layer 23A, which is magnetized in the Y) direction, that is, in the direction away from the ABS plane, and faces through the nonmagnetic intermediate layer 23B, is antiparallel to the magnetization direction of the first pinned magnetic layer 23A ( It is magnetized in the −Y) direction. The first pinned magnetic layer 23A is formed in contact with the antiferromagnetic layer 22. By performing annealing (heat treatment) in a magnetic field, the interface between the first pinned magnetic layer 23A and the antiferromagnetic layer 22 is formed. Generates an exchange coupling magnetic field (exchange anisotropic magnetic field), and the magnetization direction of the first fixed magnetic layer 23A is fixed. When the magnetization direction of the first fixed magnetic layer 23A is fixed, for example, in the height (+ Y) direction, the magnetization direction of the second fixed magnetic layer 23C opposed to the first fixed magnetic layer 23C via the non-magnetic intermediate layer 23B becomes the first magnetization direction. It is fixed in a state antiparallel to the magnetization of the fixed magnetic layer 23A.

As the exchange coupling magnetic field increases, the magnetization of the first pinned magnetic layer 23A and the magnetization of the second pinned magnetic layer 23C can be more stably maintained in the antiparallel state. The magnetic layer 22 has a high blocking temperature,
Moreover, by using a PtMn alloy that generates a large exchange coupling magnetic field at the interface with the first fixed magnetic layer 23A, the magnetization states of the first fixed magnetic layer 23A and the second fixed magnetic layer 23C are thermally stabilized. You can keep it.

Next, regarding the free magnetic layer 25, the first
The free magnetic layer 25A and the second free magnetic layer 25C have magnetic moments (magnetic thicknesses) whose sizes and directions are indicated by arrows and symbols in FIGS. 1 and 2, respectively. The magnetic moment M here is also the product of the saturation magnetization (Ms) and the film thickness (t), that is, the following equation: M = Ms · t (similar to the case of the fixed magnetic layer described above). 1 ′).

Here, when the first free magnetic layer 25A and the second free magnetic layer 25C have the same composition (consisting of a single layer), the saturation magnetization (Ms) is also substantially the same in physical properties. , The thicker the film thickness (t) is the magnetic moment (M)
Becomes larger. In this case, since the thickness of the second free magnetic layer 25C is larger, the magnitude of the magnetic moment (M) is also larger as shown in FIG.

FIG. 3 shows a magnetization curve of such a free magnetic layer 25. The horizontal axis in FIG. 3 is the externally applied magnetic field H, and the vertical axis is the magnetization M. Here, the absolute value of the applied magnetic field is H
_{Since the} antiparallel state is maintained within _SF (spin flop magnetic field), Mst is | Mst (F
2) Act as one artificial ferrimagnetic material having a small Mst of −Mst (F1) |.

Further, regarding the hard bias layer 32,
The following conditions are required between the free magnetic layer 25 and the free magnetic layer 25. The intensity (H) of a magnetic field (hereinafter, referred to as a hard bias magnetic field) acting on the free magnetic layer 25 of the hard bias layer 32
However, the magnetization of the free magnetic layer 25 is smoothly rotated by the magnetic field from the recording medium, and a track width of the free magnetic layer 25 is obtained in order to obtain a required reproduction signal without causing instability of a reproduction waveform such as bulk Hansen noise. In the middle part of the direction does not fall below a minimum value (this minimum value varies according to the track width Tw, a small amount of H);
... (Α condition) is required, and magnetization is not disturbed at the edge portion of the free magnetic layer 25 in the track width direction (to prevent disturbance of exchange coupling, disturbance of track profile and instability of reproduced waveform) In order to prevent non-uniformity of the magnetization distribution in the free magnetic layer 25 which causes the hard bias magnetic field Hmax near the edge in the track width direction.
Requires that the free magnetic layer 25 does not exceed a magnetic field (that is, a spin-flop magnetic field Hsf) that can maintain the antiparallel state with each other (β condition). The value of the spin flop magnetic field (Hsf) depends on the composition of the free magnetic layer 25.

On the other hand, when the joint shape of the hard bias film 32 with the spin valve film is constant, the intensity (H) of the hard bias magnetic field at the intermediate portion of the free magnetic layer 25 in the track width direction is And the following equation (2): H∝tb / R ⁿ = K · (tb / R) (2) where tb: film thickness of the hard bias layer 32 R; distance from the hard bias layer 32 (= Tw / 2) K: proportional constant n: 1 It is known to satisfy ２2 (integer). Here, the length dimension in the X direction of the free magnetic layer 25 is defined as a physical (optical) track width Tw.

Therefore, from the expression (2), the free magnetic layer 2
In the case where the strength (H) of the hard bias magnetic field at the intermediate portion in the track width direction is constant, the hard bias layer 32
If the distance (R) between them, that is, the track width Tw is reduced,
It is understood that the thickness (tb) of the hard bias layer 32 may be small. For example, in this embodiment, specifically, when the track width Tw is 0.4 μm, the hard bias layer 3
2 has a lower limit of 20 nm, and when the track width Tw is 0.3 μm, the lower limit of the thickness of the hard bias layer 32 is 13 nm. When the track width Tw is 0.2 μm, the lower limit of the thickness of the hard bias layer 32 is 10 nm.

As will be described later, according to the present invention, the track width Tw of the free magnetic layer 25, in other words,
The distance (R) between the hard bias layers 32 is configured to be narrowed to a certain range.
Even if the film thickness (tb) is reduced, the strength (H) of the hard bias magnetic field can be secured to a required magnitude. In other words, if the distance (R) between the hard bias layers 32 is reduced, the strength of the hard bias magnetic field at the intermediate portion of the free magnetic layer 25 in the track width direction is obtained even if the thickness (tb) of the hard bias layer 32 is small. (H) can be kept constant.

Next, while maintaining good reproducing characteristics in a (thermally) stable state, the magnetization (shown in FIG. 10) which has conventionally occurred (shown in FIG. 10) near the edge portion of the free magnetic layer 25 in the track width direction. The conditions for preventing the disturbance (frustration) will be described with reference to FIG. This FIG.
The horizontal axis indicates the track width Tw and the vertical axis indicates the magnetic field. The magnetic field (Hmax) received by the free magnetic layer 25 from the hard bias layer 32 and the spin-flop magnetic field (Hsf) of the free magnetic layer 25 are also shown. (Hmax) is the magnetic field near the track edge when the minimum required thickness of the hard bias layer 32 is provided to satisfy the above-described condition.

The strength (H) of the hard bias magnetic field is necessary without causing the magnetization of the free magnetic layer 25 to rotate smoothly due to the magnetic field from the recording medium and causing distortion or instability of the reproduction waveform such as Barkhausen noise. In order to obtain a reproduced signal, the free magnetic layer 25 is set so as not to fall below the minimum value (H0) at an intermediate portion in the track width direction. Further, the strength (H) of the hard bias magnetic field varies according to the width of the track width Tw from the equation (2). Therefore,
Formulating the above condition α, H> H0 (α) where H0; (constant) constant

In the vicinity of the edge of the free magnetic layer 25 in the track width direction, that is, the hard bias layer 32
Bias magnetic field Hmax in the portion close to
Is given by the following equation (3). Hmax @ tb = K ′ · tb (3) where tb: film thickness of the hard bias layer 32 K ′: proportional constant

As can be seen from the above equation (2), when the track width Tw is wide, a large hard bias layer thickness tb is required to obtain the required H (> H0). This increases the hard bias magnetic field near the track edge. In other words, even if the magnetic field H is the same in the middle part in the track width direction, the smaller the track width, the smaller the magnetic field Hmax near the track edge. This magnetic field Hmax must not exceed the spin flop magnetic field (Hsf) of the free magnetic layer 25 (β condition). By formulating this, Hmax <Hsf (.beta.) Holds.

The composition of the first free magnetic layer 25A and the second free magnetic layer 25C of the free magnetic layer 25 is made of CoFeNi. As a result, the maximum allowable magnetic field strength, that is, the strength of the spin-flop magnetic field (Hsf) is made smaller than that of the conventional free magnetic layer having a composition of NiFe. , 59 (kA / m) (indicated by a broken line in FIG. 4), from the case of C, for example, CoFeNi, 293 (kA / m).
m) (condition β shown by a dashed line in FIG. 4) can be greatly increased (raised to the bottom).

In this case, the hard bias film thickness satisfying the condition of Hmax <Hsf is about 50 nm or less. However, when the track width is narrow, the reproduction sensitivity is reduced when the hard bias film thickness is 50 nm. Therefore, when the track width is 0.3 μm or less, 40 nm or less, and when the track width is 0.2 μm or less, 35 nm or less. It is preferred that

In addition, the expression of the condition α, H> H0 (2)
Substituting equation, than ^{K · (tb / R n)} > H0 (3) equation, since tb = Hmax / K', with (K / K') · (Hmax / R n)> the H0 R Tw / 2 In other words, the expression of the condition α is as follows. Hmax> K ″ · Tw (α ′) where n; 1-2 (integer) K ″; constant (= (k ′ · H0) / (2 ⁿ · K))

In the conventional free magnetic layer using NiFe, since Hsf was small, there was no region satisfying the equations (α ′) and (β) at the same time. However,
In the present invention, since the Hsf can be increased, the shaded region in FIG. 4 can ensure a region that satisfies the condition (2), that is, the condition (α ′) and the condition (β) at the same time. Become. In the hard bias layer 32, a rightward hard bias magnetic field is applied to the free magnetic layer 25 in FIG. 1, but when the track width is narrow as described above, the hard bias layer 32 is thinned. Therefore, the intensity of the hard bias magnetic field acting on the track edge portion can be reduced.

As a result, the first free magnetic layer 25A and the second free magnetic layer 25A near the track edge are maintained while maintaining good reproduction sensitivity characteristics in which the magnetization in the free magnetic layer 25 rotates smoothly due to the magnetic field from the recording medium. Magnetic layer 25C
It is possible to prevent the disturbance (frustration) of the magnetization in. FIG. 5 shows the results of a magnetic field simulation of the distribution of the magnetization direction in the first free magnetic layer 25A and the second free magnetic layer 25C when the physical track width (optical track width) is 0.4 μm. Here, the first free magnetic layer 25A is made of Co ₈₇ Fe ₁₁ Ni ₂ and has a thickness of 1.4 nm, the second free magnetic layer 25C is made of Co ₈₇ Fe ₁₁ Ni ₂ and has a thickness of 2.4 nm and has a hard bias. The layer 32 is made of a CoPt alloy and has a thickness of 40 nm, and the total magnetic flux is a remanent magnetization (Mr) × the thickness (nm) of 38 (T × nm). 5 that the disturbance (frustration) of the magnetization in the first free magnetic layer 25A and the second free magnetic layer 25C near the track edge portion is suppressed as compared with FIG. 10 showing the conventional example. .

The CoFe used for the free magnetic layer 25
The composition ratio of the Ni alloy is preferably limited. This is due to the following. For example, if the SFF structure is CoFeN
In the case of i / Ru / CoFeNi, the magnetostriction of CoFeNi changes to a positive side of 1 to 6 ppm by contact with the nonmagnetic intermediate layer. Therefore, taking this change into account, the composition range is limited as follows. (I) When Fe> 17 at% (hereinafter abbreviated as “at%”), the magnetostriction becomes too negative and the soft magnetic properties deteriorate. (Ii) If Fe <9 at%, the magnetostriction becomes too large and the soft magnetic properties deteriorate. (Iii) When Ni> 10 at%, the magnetostriction becomes positive, and ΔR and ΔR / R deteriorate due to diffusion of the nonmagnetic conductive layer (Cu) and Ni. The characteristics deteriorate. (Iv) When Ni <0.5 at%, the magnetostriction becomes negatively large.

Under these circumstances, the composition range of the CoFeNi alloy is 9 at% ≦ Fe ≦ 17 at% or less, 0.5 at% ≦ Ni ≦ 10 at% or less, with the balance being Co. Further, by setting the composition range of the CoFeNi alloy, the Co magnetic constituting the free magnetic layer can be formed.
When the magnetostriction constant of the FeNi alloy film is −3 × 10 ⁻⁶ or more, +3
The coercive force can be set to 790 (A / m) or less within a range of × 10 ^-6 or less. If the magnetostriction is large, the film is likely to be affected by stress (magnetoelastic effect or inverse magnetostriction effect) due to film forming strain or a difference in thermal expansion coefficient between other layers. Since the free magnetic layer 25 and the magnetization direction are disturbed, it is preferable that the absolute value of the magnetostriction is small. Further, the coercive force is preferably small. By suppressing the coercive force to 790 (A / m) or less, magnetization reversal with respect to a signal magnetic field can be improved, that is, good soft magnetic characteristics can be obtained. .

In the present invention, the diffusion preventing film made of CoFe is provided between the nonmagnetic conductive layer 24 and the second free magnetic layer 25C, that is, the nonmagnetic conductive layer 24 is connected to the first free magnetic layer 25C. The atoms constituting each layer up to 25A are Cu / CoFe / CoFeNi / Ru / CoFeN
i may be used, but in this case, the composition ratio is preferably limited to the following. That is, the preferred composition range of the CoFeNi alloy is 7 at% ≦ Fe ≦ 15 at% 5 at% ≦ Ni ≦ 15 at% The balance is Co (however, strictly speaking, it depends on the CoFeNi layer thickness).

Here, as described above, that is, this C
By setting the composition range of the oFeNi alloy,
The magnetostriction constant of the CoFeNi alloy film constituting the conductive layer is -3 ×
10 ^-6With the above, + 3 × 10^-6Coercive force 79 in the following range
0 (A / m) or less. Large magnetostriction
Due to film formation strain and the difference in thermal expansion coefficient between other layers.
The effect of stress (magnetoelastic effect or inverse magnetostriction effect)
And heat generated by heat treatment during the thin film process.
The free magnetic layer and the magnetization direction are disturbed by stress etc.
It is preferable that the absolute value of the magnetostriction is small. Also, the coercive force
Is preferably small, and the coercive force should be 790 (A / m) or less.
The magnetization reversal to the signal magnetic field
Good, that is, good soft magnetic properties can be obtained.
You can do it.

The reason for limiting to such a composition ratio is that Co is
Since Fe has minus magnetostriction, CoFeNi / Ru /
This is because Fe is slightly lower than CoFeNi, and Ni is preferably slightly higher. (I) If Fe> 15 at%, the magnetostriction becomes too negative and the soft magnetic properties deteriorate. (Ii) When Fe <7 at%, the magnetostriction becomes too large and the soft magnetic property is deteriorated. (Iii) When Ni> 15 at%, the magnetostriction becomes positively large (however, this is not a problem because the CoFe layer is in contact with the Cu layer). (Iv) When Ni <5 at%, the magnetostriction becomes negatively large.

In this embodiment, the spin-valve thin-film element 2 has a GMR (gian
Although a bottom spin-valve magnetoresistive element, which is a type of a magnetoresistive element, is used, for example, a top spin-valve or dual spin-valve magnetoresistive element may be used. . Also,
The pinned magnetic layer may be a single layer as a spin-valve thin film element exhibiting the magnetoresistance effect.

Hereinafter, these specific configurations will be described. In this embodiment, the same parts as those in the previous embodiment are denoted by the same reference numerals, and redundant description will be avoided. FIG. 6 shows another type of magnetoresistive element 2 of the present invention.
This magnetoresistive element 2 'is of a top spin valve type. Multilayer film 20 'constituting the top spin valve type magnetoresistive element 2'
Is different from the above-described multilayer film 20 ′ constituting the bottom spin valve type, in which the seed layer (underlayer) 21 is formed.
Upper layers are stacked in the opposite order of the stacking order of each layer.

That is, in the top spin-valve magnetoresistive element, the multilayer film 20 in the track region is formed from the bottom in order of the seed layer (base layer) 21, the second free magnetic layer 25C, and the nonmagnetic intermediate layer. 25B, a first free magnetic layer 25A composed of two layers, a nonmagnetic conductive layer 24, a second fixed magnetic layer 23C, a nonmagnetic intermediate layer 23B, a first fixed magnetic layer 23A, an antiferromagnetic layer 22, The protective layer 26 is laminated.

The first free magnetic layer 25A is composed of a diffusion prevention film 25D made of a CoFe alloy or Co, which is in contact with the nonmagnetic conductive layer 24, and a NiFe alloy, a CoFe alloy or
The ferromagnetic film 25E is made of an oNiFe alloy. The diffusion prevention film 25D is also formed of a ferromagnetic material. The diffusion prevention film 25D is formed of Cu or the like to prevent diffusion of metal elements and the like at the interface with the nonmagnetic conductive layer 24. , ΔMR (resistance change rate) is increased.

Next, still another embodiment will be described with reference to FIG. In this embodiment, the same parts as those of the previous embodiment are denoted by the same reference numerals, and the description thereof will not be repeated. FIG. 7 shows another type of magnetoresistive element 2 '' of the present invention, and this magnetoresistive element 2 '' also constitutes a dual spin valve type. This dual spin valve type magnetoresistive element 2
The multilayer film 20 ″ constituting the ″ ″ differs from the multilayer film 20 ′ constituting the above-described top spin valve type,
The portion above the seed layer layer (underlying layer) 21 has the nonmagnetic conductive layer 2 above and below the free magnetic layer 25.
4, 27, fixed magnetic layers 23, 28, and antiferromagnetic layer 2
2 and 29 are stacked. In each of these layers, the free magnetic layer 25 and the pinned magnetic layer 23 are separated into two layers via a non-magnetic intermediate layer.

That is, the multilayer film 20 ″ is composed of a seed layer (underlayer) 21, an (lower) antiferromagnetic layer 22, a (lower) fixed magnetic layer 23, and a ), The nonmagnetic conductive layer 24, the free magnetic layer 25, the (upper) nonmagnetic conductive layer 27, the (upper) fixed magnetic layer 28, the (upper) antiferromagnetic layer 29, and the protective layer 26 are laminated. is there.

The lower fixed magnetic layer 23 includes a first fixed magnetic layer 23A and a non-magnetic intermediate layer 23 in order from the bottom.
B and the second pinned magnetic layer 23C. The free magnetic layer 25 is ranked from the bottom, and the second free magnetic layer 25C
, A non-magnetic intermediate layer 25B, and a first free magnetic layer 25A.
And the second free magnetic layer 25C
Consists of a ferromagnetic film 25G and a diffusion prevention film 25F from below. The first free magnetic layer 25A includes an intrinsic film 25E and a diffusion prevention film 25D from below. Further, the diffusion prevention films 25G and 25E are also formed of a ferromagnetic material.

On the other hand, the upper fixed magnetic layer 28 includes, in order from the bottom, a second fixed magnetic layer 28C and a non-magnetic intermediate layer 28B.
And the first pinned magnetic layer 28A. These are formed of the same material as the lower fixed magnetic layer 23. Note that the upper nonmagnetic conductive layer 27 is
4 and the upper antiferromagnetic layer 29 is formed of the same material as the lower antiferromagnetic layer 22. Also, different materials may be used for the upper and lower antiferromagnetic materials. Similarly, different materials may be used for the upper and lower fixed magnetic layers and nonmagnetic conductive layers.

[0074]

As described above, according to the present invention, the free magnetic layer provided on the multilayer film of the single spin valve bottom spin valve type or top spin valve type magnetoresistive element is a magnetic layer / intermediate layer. Ferrite-free (SFF) structure having three layers of a magnetic layer / intermediate layer / magnetic layer. Each composition of the magnetic layer / intermediate layer / magnetic layer has (A) CoFeNi / Ru
/ CoFeNi, (B) CoFeNi / Ru / CoF
e, (C) CoFe / CoFeNi / Ru / CoFeN
i or (D) CoFe / CoFeNi / Ru / Co
Fe, and in the case of (A) and (B), the CoFeN
The composition of the i-alloy layer is atomic%, 9 ≦ Fe ≦ 17 0.5 ≦ Ni ≦ 10 The balance is Co, and in the case of (C) and (D), 7 ≦ Fe ≦ 15 5 ≦ Ni ≦ 15 It is characterized in that the balance is Co.

In the case of the dual spin-valve magnetoresistive element, the free magnetic layer provided on the other layer has a synthetic ferri-free (SFF) structure having three layers of a magnetic layer / intermediate layer / magnetic layer. The composition of the magnetic layer / intermediate layer / magnetic layer magnet is determined by (E) CoFeNi / Ru / CoFeNi from the side in contact with the lower nonmagnetic conductive layer.
(F) CoFe / CoFeNi / Ru / CoFeNi /
In the case of (E), 9 ≦ Fe ≦ 17 0.5 ≦ Ni ≦ 10 The balance is Co, and in the case of (F), 7 ≦ Fe ≦ 155 5 ≦ Ni ≦ 15 The balance is Co.

Therefore, according to the present invention, the magnetization direction in the free magnetic layer can be rotated with high sensitivity by the external magnetic field from the recording medium in a stable state, and at the same time, the hard bias The disturbance of the direction of magnetization near the edge of the free magnetic layer due to the layer can also be prevented. As a result, a spin-valve thin-film element having a laminated ferri-free structure, which has conventionally been difficult to be practically used due to poor compatibility with the hard bias layer, can achieve a good reproduction sensitivity.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a magnetoresistive element according to an embodiment of the present invention as viewed from an ABS.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a graph showing a magnetization curve of a free magnetic layer in the magnetoresistive element of FIG.

FIG. 4 is a graph showing a relationship between a track width and a strength of a hard bias magnetic field near a track edge in the magnetoresistive element shown in FIG.

FIG. 5 is an explanatory diagram showing a distribution of a magnetization direction near an edge of a free magnetic layer in the magnetoresistance effect element according to the present invention.

FIG. 6 is a cross-sectional view showing a magnetoresistive element according to another embodiment as viewed from the ABS.

FIG. 7 shows a magnetoresistive element according to still another embodiment of the present invention;
It is sectional drawing which shows the state seen from S side.

FIG. 8 is a cross-sectional view showing a state in which a conventional magnetoresistive element is viewed from the ABS.

FIG. 9 is a cross-sectional view showing a state in which another conventional magnetoresistance effect element is viewed from the ABS.

FIG. 10 is an explanatory diagram showing disturbance (frustration) in the direction of magnetization in the vicinity of an edge of a free magnetic layer in a conventional magnetoresistive element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Substrate 12 Shield layer 13 Lower gap layer 2 Spin valve thin film element 21 Seed layer layer 22 Antiferromagnetic layer 23 Fixed magnetic layer 23A First fixed magnetic layer 23B Non-magnetic intermediate layer 23C Second fixed magnetic layer 24 Non-magnetic Conductive layer 25 Free magnetic layer 25A First free magnetic layer 25B Nonmagnetic intermediate layer 25C Second free magnetic layer 25D Diffusion prevention film 26 Protective layer 27 (Upper) nonmagnetic conductive layer 28 (Upper) fixed magnetic layer 29 (Upper) antiferromagnetic layer 31 bias underlayer 32 hard bias layer 33 intermediate layer 34 electrode layer F1 first free magnetic layer F2 second free magnetic layer Hs Saturated magnetic field Hsf Spin flop magnetic field Ms Saturated magnetization SFF Synthetic ferri Free SFP Synthetic Ferri Pinned Tw Track width tb (Hard bias layer) film X track width direction Y height direction Z stacking direction α magnetization of smooth rotation of the conditions (hard bias film thickness) beta magnetization disturbance prevention of conditions at the edge portion (track width)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 10/32 G01R 33/06 R (72) Inventor Kenichi Tanaka 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) Inventor Yosuke Ide 1-7 Yukitani Otsuka-cho, Ota-ku, Tokyo Alps Electric Co., Ltd. F-term (reference) 2G017 AA10 AD55 5D034 BA02 BA03 5E049 AA04 AA09 AC05 BA12 BA16 DB12

Claims (12)

[Claims] 1. A magnetic device comprising: a multilayer film exhibiting a magnetoresistive effect; hard bias layers provided on both side regions of the multilayer film on both sides in a track width direction; and an electrode layer laminated on the hard bias layer. The resistance effect element, wherein the free magnetic layer provided in the multilayer film has a synthetic ferri-free (SFF) structure including a first magnetic layer / a non-magnetic intermediate layer / a second magnetic layer. The magnetic intermediate layer is made of Ru, at least one of the first magnetic layer and the second magnetic layer is made of a CoFeNi alloy, and the composition ratio of the CoFeNi alloy is such that Fe is 9 at.% Or more and 17 at. A magnetoresistive element comprising at least 5 atomic% and at most 10 atomic%, with the balance being Co. 2. The fixed magnetic layer, wherein the multilayer film is formed in contact with the antiferromagnetic layer and the antiferromagnetic layer, and whose magnetization direction is fixed by an exchange anisotropic magnetic field with the antiferromagnetic layer. And a nonmagnetic conductive layer formed between the pinned magnetic layer and the free magnetic layer, wherein the second magnetic layer is disposed between the nonmagnetic conductive layer and the nonmagnetic intermediate layer, The first and second magnetic layers are made of CoFeN.
2. The magnetoresistive element according to claim 1, wherein the element is formed of an i-alloy. 3. The fixed magnetic layer, wherein the multilayer film is formed in contact with the antiferromagnetic layer and the antiferromagnetic layer, and the magnetization direction is fixed by an exchange anisotropic magnetic field with the antiferromagnetic layer. And a non-magnetic conductive layer formed between the fixed magnetic layer and the free magnetic layer, wherein the second magnetic layer is disposed between the non-magnetic conductive layer and the non-magnetic intermediate layer; The magnetoresistance effect element according to claim 1, wherein the two magnetic layers are formed of a CoFeNi alloy, and the first magnetic layer is formed of a CoFe alloy. 4. An antiferromagnetic layer, a fixed magnetic layer formed in contact with the antiferromagnetic layer and whose magnetization direction is fixed by exchange anisotropy with the antiferromagnetic layer, the fixed magnetic layer and the nonmagnetic conductive layer A multilayer film having a free magnetic layer sandwiched therebetween, and exhibiting a magnetoresistive effect, a hard bias layer provided on both sides of the multilayer film, and an electrode layer laminated on the hard bias layer. Wherein the free magnetic layer provided in the multilayer film has a synthetic ferri-free (SFF) structure having three layers of a first magnetic layer / non-magnetic intermediate layer / second magnetic layer. A second magnetic layer disposed between the nonmagnetic conductive layer and the nonmagnetic intermediate layer; a magnetic layer made of a CoFe alloy formed between the second magnetic layer and the nonmagnetic conductive layer; The layer is made of Ru and the second magnetic layer is made of CoFe Consists i, the composition ratio of CoFeNi alloy, Fe 7 atomic% to 15 atomic% or less, Ni is 5 atomic% to 15 atomic% or less,
A magnetoresistive element, wherein the remainder is made of Co. 5. A free magnetic layer having a track width of 0.1
4 μm or less and the thickness of the hard bias layer is 20 n
5. The structure according to claim 1, wherein the distance is from m to 50 nm.
The magnetoresistive element according to any one of the above items. 6. A free magnetic layer having a track width of 0.
3 μm or less, and the thickness of the hard bias layer is 13 n
5. The structure according to claim 1, wherein the distance is from m to 40 nm.
The magnetoresistive element according to any one of the above items. 7. A free magnetic layer having a track width of 0.
2 μm or less, and the thickness of the hard bias layer is 10 n
5. The structure according to claim 1, wherein the distance is from m to 35 nm.
The magnetoresistive element according to any one of the above items. 8. The thin film device according to claim 1, wherein the multilayer film is a bottom-type spin-valve thin-film device including an antiferromagnetic layer, a fixed magnetic layer, a nonmagnetic conductive layer, and a free magnetic layer in order from the bottom. 8. The magnetoresistance effect element according to any one of 1 to 7. 9. A top-type spin-valve thin-film element comprising a free magnetic layer, a non-magnetic conductive layer, a fixed magnetic layer, and an antiferromagnetic layer in order from the bottom. 8. The magnetoresistance effect element according to any one of 1 to 7. 10. The multilayer film is formed on a free magnetic layer, a nonmagnetic conductive layer formed above and below the free magnetic layer, and above one nonmagnetic conductive layer and below the other nonmagnetic conductive layer. 8. A fixed magnetic layer having a fixed magnetization direction, and an antiferromagnetic layer formed on one fixed magnetic layer and below the other fixed magnetic layer. The magnetoresistive element according to any one of the above items. 11. A seed layer is formed under the antiferromagnetic layer or under the free magnetic layer.
11. The magnetoresistive element according to any one of claims 10 to 10. 12. A thin-film magnetic head comprising the magnetoresistive element according to claim 1. Description: