JPH1065232A - Magnetoresistive effect device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a magnetoresistive effect device with a spin valve film from dissipating heat, so as to improve it in thermal stability without deteriorat ing its performance. SOLUTION: A magnetoresistive effect device is equipped with a spin valve film 7, composed of a first magnetic layer 1 formed on a metal buffer layer 4, a non-magnetic intermediate layer 3 and a second magnetic layer 2. An atom diffusion barrier layer 5 formed of oxide, nitride, carbide, boride, fluoride or the like of thickness 2nm or below is provided at an interface between the metal buffer layer 4 and the first magnetic layer 1. Or a magnetoresistive effect device is equipped with a spin valve film 7, composed of a first magnetic layer of laminated film structure which consists of a magnetic base layer and a ferromagnetic layer, a second magnetic layer, and a non-magnetic intermediate layer interposed between them, wherein an atom diffusion barrier layer formed of oxide, nitride, carbide, boride, fluoride or the like of thickness 2nm or below is provided at an interface between the magnetic base layer and the ferromagnetic layer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetoresistive element using a spin valve film.

[0002]

2. Description of the Related Art Generally, when reading information recorded on a magnetic recording medium, a reproducing magnetic head having a coil is moved relative to the recording medium, and the magnetic induction is induced on the coil by electromagnetic induction generated at that time. This has been done by a method that detects the voltage that On the other hand, it is also known to use a magnetoresistance effect element (hereinafter, MR element) when reading information (see IEEE MAG-7, 150 (1971), etc.). A magnetic head using an MR element (hereinafter, referred to as an MR head) utilizes a phenomenon that the electric resistance of a certain ferromagnetic material changes according to the strength of an external magnetic field.

In recent years, the size and capacity of magnetic recording media have been reduced, and the relative speed between the reproducing magnetic head and the magnetic recording medium at the time of reading information has been reduced. Expectations for an MR head capable of extracting output are increasing. Here, a Ni-Fe alloy, a so-called permalloy-based alloy, has been used for a portion where the resistance is changed by sensing an external magnetic field of the MR head (hereinafter referred to as an MR element). However, even though permalloy alloys have good soft magnetic properties, the rate of change in magnetoresistance is at most about 3%, and the rate of change in magnetoresistance is small for MR elements for small and large-capacity magnetic recording media. Not enough. Therefore, a material exhibiting a more sensitive magnetoresistance effect is desired as an MR element material.

In response to such demands, Fe / Cr and C
Like o / Cu, ferromagnetic metal films and non-magnetic metal films are alternately stacked under certain conditions, and a multilayer film in which adjacent ferromagnetic metal films are antiferromagnetically coupled, that is, a so-called artificial lattice film is huge. It has been confirmed that a high magnetoresistance effect is exhibited. According to the artificial lattice film, a large magnetoresistance change rate exceeding 100% has been reported (Phys. Rev. Lett., Vol. 61, 24).
74 (1988), Phys. Rev. Lett., Vol. 64, 2304 (1990), etc.). However, since the artificial lattice film has a high saturation magnetic field, M
Not suitable for R element.

On the other hand, there has been reported an example in which a multilayer film having a sandwich structure of a ferromagnetic layer / a nonmagnetic layer / a ferromagnetic layer realizes a large magnetoresistance effect even when the ferromagnetic layer does not have antiferromagnetic coupling. That is, an exchange bias is applied to one of the two ferromagnetic layers sandwiching the non-magnetic layer to fix the magnetization, and the other ferromagnetic layer is magnetized by an external magnetic field (such as a signal magnetic field). Thus, a large magnetoresistance effect can be obtained by changing the relative angle between the magnetization directions of the two ferromagnetic layers disposed with the nonmagnetic layer interposed therebetween. This type of multilayer film is called a spin valve film (Phys. Rev. B., Vol. 45, 806 (1992), J. Appl. Phys., Vol. 6).
9, 4774 (1991)). Although the spin valve film has a smaller rate of change in magnetoresistance than the artificial lattice film, it can saturate the magnetization in a low magnetic field, and thus is suitable for the MR element. The MR head using such a spin valve film is expected to have great practical use.

[0006]

In the MR element using the above-described spin valve film, it is important to improve the soft magnetic characteristics by increasing the crystal orientation of the ferromagnetic layer. For example, in a spin valve film using a Co-based ferromagnetic material such as Co or a Co-based alloy for the ferromagnetic layer, if a Co-based ferromagnetic layer is formed directly on an amorphous material, the crystal orientation decreases. In addition, the soft magnetic characteristics are deteriorated. Therefore, it has been studied to increase the crystal orientation by forming a metal film having an fcc crystal structure as a buffer layer and forming a Co-based ferromagnetic layer on the metal buffer layer.

However, when a soft magnetic material such as a NiFe alloy is used for the metal buffer layer,
Thermal diffusion easily occurs with the o-based ferromagnetic material, and the magnetoresistance effect deteriorates. Also, in order to enhance the soft magnetic properties of the spin valve film and improve the device sensitivity, it has been studied to form a ferromagnetic layer whose magnetization is reversed by an external magnetic field on a magnetic underlayer made of various soft magnetic materials. However, even in such a case, thermal diffusion occurs between the ferromagnetic layer and the magnetic underlayer, and the magnetoresistance effect deteriorates.

In the manufacturing process of an MR element using a spin valve film, heat treatment is indispensable, so that the above-mentioned deterioration of the magnetoresistance effect due to thermal diffusion is a serious problem. As described above, the MR element using the conventional spin valve film has a problem that thermal stability (heat resistance) is low, and improvement of thermal stability by suppressing thermal diffusion has become a major issue. .

The present invention has been made to address such a problem, and has as its object to provide a high-performance magnetoresistive element having excellent thermal stability by suppressing thermal diffusion. .

[0010]

According to a first aspect of the present invention, there is provided a first magnetoresistive element, comprising: a first magnetic layer formed on a metal buffer layer; and a second magnetic layer. And a spin valve film having a nonmagnetic intermediate layer disposed between the first magnetic layer and the second magnetic layer, wherein the metal buffer layer and the first magnetic layer An atomic diffusion barrier layer having an average thickness of 2 nm or less is provided at the interface with the substrate.

The first magnetoresistive element may further include: a first magnetic layer made of a ferromagnetic material containing Co formed on a metal buffer layer having an fcc crystal structure; A magnetoresistive element including a spin valve film having a second magnetic layer and a non-magnetic intermediate layer disposed between the first magnetic layer and the second magnetic layer; At the interface with the first magnetic layer, an atomic diffusion barrier layer mainly composed of at least one selected from oxides, nitrides, carbides, borides and fluorides is provided.

According to a second aspect of the present invention, there is provided a second magnetoresistive element, comprising: a first magnetic layer comprising a laminated film of a magnetic underlayer and a ferromagnetic layer; A magnetoresistive element comprising a spin valve film having a layer and a non-magnetic intermediate layer disposed between the first magnetic layer and the second magnetic layer, wherein the magnetic underlayer and the ferromagnetic layer An atomic diffusion barrier layer having an average thickness of 2 nm or less is provided at the interface with the substrate.

The second magnetoresistive element may further include a first magnetic layer comprising a laminated film of a magnetic underlayer and a ferromagnetic layer containing Co, and a second magnetic layer. A magnetoresistive element comprising a spin valve film having a layer and a non-magnetic intermediate layer disposed between the first magnetic layer and the second magnetic layer, wherein the magnetic underlayer and the ferromagnetic layer Is provided with an atomic diffusion barrier layer containing, as a main component, at least one selected from oxides, nitrides, carbides, borides, and fluorides.

In the first magnetoresistance effect element, since the above-described atomic diffusion barrier layer is provided at the interface between the metal buffer layer and the first magnetic layer, the metal buffer layer and the first magnetic layer during the heat treatment are provided. In addition, the interdiffusion of atoms with the magnetic layer can be suppressed well, and the effect of improving the film quality of the first magnetic layer by the metal buffer layer can be obtained. Therefore,
A good magnetoresistance effect can be stably obtained after the heat treatment, and at the same time, a good soft magnetic property can be obtained.

In the second magnetoresistive element, the above-described atomic diffusion barrier layer is provided at the interface between the magnetic underlayer and the ferromagnetic layer. Atomic mutual diffusion with the ferromagnetic layer can be suppressed well. Therefore, a good magnetoresistance effect can be stably obtained after the heat treatment.

[0016]

Embodiments of the present invention will be described below.

First, an embodiment for implementing the first magnetoresistance effect element (MR element) of the present invention will be described.

FIG. 1 is a cross-sectional view showing a main configuration of an embodiment of the first MR element. In the figure, 1 is a first magnetic layer, 2 is a second magnetic layer, and a non-magnetic intermediate layer 3 is interposed between the first and second magnetic layers 1 and 2. There is no antiferromagnetic coupling between these magnetic layers 1 and 2,
It constitutes a non-bonded laminated film.

The first and second magnetic layers 1 and 2 are made of, for example, a ferromagnetic material containing Co such as Co alone or a Co-based magnetic alloy, or a ferromagnetic material such as a NiFe alloy. Among these, as the ferromagnetic material containing Co, use of a Co-based magnetic alloy which can increase both the bulk effect and the interface effect, which particularly affect the MR change amount, and thereby obtain a large MR change amount can be used. Is preferred.

As the Co-based magnetic alloy as described above,
Fe, Ni, Au, Ag, Cu, Pd, Pt, I
An alloy to which one or more of r, Rh, Ru, Os, Hf and the like are added is given. Addition element amount is 5 to 50 atomic%
And more preferably in the range of 8 to 20 atomic%. This is because if the amount of the added element is too small, the bulk effect does not sufficiently increase, and if the amount of the added element is too large, the interface effect may be greatly reduced. In order to obtain a large MR change amount, it is particularly preferable to use Fe as an additional element.

The thickness of the first and second magnetic layers 1 and 2 is preferably in the range of 1 to 30 nm so that a large MR change can be obtained and Barkhausen noise can be suppressed. .

Of the above-mentioned magnetic layers 1 and 2, the first magnetic layer 1 is formed on the metal buffer layer 4, thereby improving the film quality by improving the crystal orientation of the first magnetic layer 1. Have been. The first magnetic layer 1 is made of Co as described above.
When a ferromagnetic material containing is used, the metal buffer layer 4 may be made of a metal material having an fcc crystal structure, for example, a NiFe alloy, a NiFeCo alloy, or an alloy having the fcc crystal structure.
i, V, Cr, Mn, Zn, Nb, Mo, Tc, Hf,
An alloy having an increased resistance by adding an additional element such as Ta, W, or Re is exemplified. Among them, NiFe alloy and Ni
The FeCo alloy or the like also functions as a magnetic underlayer described later. When a ferromagnetic material such as a NiFe alloy is used for the first magnetic layer 1, Ta, Ti, Cr, C
u, Au, Ag, and alloys thereof can be used as the metal buffer layer 4. The first magnetic layer 1 is a magnetic layer whose magnetization is reversed by an external magnetic field such as a signal magnetic field, that is, a so-called free magnetic layer.

At the interface between the first magnetic layer 1 and the metal buffer layer 4, an atomic diffusion barrier layer 5 is formed, so that the first magnetic layer 1 and the metal buffer The thermal diffusion of atoms during the period is suppressed.
That is, by forming the atomic diffusion barrier layer 5, it is possible to suppress the deterioration of the magnetoresistance effect due to thermal diffusion, and the thermal stability of the MR element is improved. The atomic diffusion barrier layer 5 is thermally stable and needs to suppress the interdiffusion of atoms between the first magnetic layer 1 and the metal buffer layer 4. Since the effect cannot be obtained, it is desirable to reduce the thickness as long as the effect of suppressing the mutual diffusion of atoms is not adversely affected. For this reason, the thickness of the atomic diffusion barrier layer 5 is 2 nm in average thickness.
It is as follows. However, if it is too thin, its function as an atomic diffusion barrier will be impaired.
It is preferable to make the above.

The constituent materials of the atomic diffusion barrier layer 5 include:
Thermally stable oxides, nitrides, carbides, borides, fluorides, and the like can be used, and these are not limited to being used alone, and may be used in the form of a mixture or a composite compound. Of these, a self-oxide film, a surface oxide film, a passivation film, and the like, which are particularly easy to form and have an excellent atom diffusion suppressing function, are preferably used. The atomic diffusion barrier layer 5 made of these compounds is formed by forming the metal buffer layer 4 and then exposing the surface to the atmosphere or exposing it to an atmosphere containing oxygen, nitrogen, carbon, boron, fluorine, or the like. can do. Further, it can also be formed by using an ion implantation method, exposing to plasma, or the like.

The compound constituting the atomic diffusion barrier layer 5 does not need to have a stoichiometrically accurate composition, does not need to form a clean crystal lattice, and may be in an amorphous state. Further, the form of the atom diffusion barrier layer 5 does not have to cover the surface of the metal buffer layer 4 uniformly, but may be, for example, a state in which a pinhole is formed, the above-described oxide, nitride, carbide, and borane. monster,
It may be formed in a discontinuous state, such as a state in which fluorides and the like exist in an island shape. It is more preferable that pinholes and the like are present to such an extent that the effect of suppressing the mutual diffusion of atoms is not adversely affected. This is because the effect of improving the film quality and the magnetic coupling may be reduced. In consideration of the above points, it is preferable that the average size of the pinholes is equal to or smaller than the distance between the adjacent pinholes.

On the other hand, the bias magnetic field of the second magnetic layer 2 is increased by an antiferromagnetic layer 6 formed of an IrMn film, a FeMn film, a NiO film, or the like, or a hard magnetic layer formed of a CoPt film or the like. This is a so-called pinned magnetic layer provided and fixed in magnetization. The second magnetic layer 2 serving as the pinned magnetic layer is not limited to the above-described one in which the magnetization of the ferromagnetic layer is fixed by the antiferromagnetic layer 6 or the like. You can also.

Here, in order to improve the linear response of the MR element, the magnetization directions of the first magnetic layer 1 and the second magnetic layer 2 should be orthogonal, for example, in a state where the external magnetic field is zero. preferable. Such a magnetized state can be obtained, for example, by performing an annealing process as described below. That is, (1) While applying a magnetic field of about 1 kOe,
After holding for about 1 hour at about temperature, (2) 1kO
Cool to a temperature of about 483K in a magnetic field of about e, (3) 483K
When the temperature reaches approximately, the direction of application of the magnetic field is rotated by 90 ° to cool to room temperature. By such an annealing process (hereinafter, referred to as orthogonal annealing), orthogonal magnetization states can be stably obtained. Specifically, the magnetization direction of the first magnetic layer 1 is defined as the track width direction, and the magnetization direction of the second magnetic layer 2 is defined with respect to the medium facing surface orthogonal to the magnetization direction of the first magnetic layer 1. It is preferable that the direction is vertical.

The annealing treatment for the first and second magnetic layers 1 and 2 is not limited to the orthogonal annealing described above.
It is also performed to improve the crystallinity of the first and second magnetic layers 1 and 2. In this case, annealing is performed at a temperature of about 100 to 400 K for about 1 minute to 10 hours.

The nonmagnetic intermediate layer 3 disposed between the magnetic layers 1 and 2 is made of a paramagnetic material, a diamagnetic material, an antiferromagnetic material, a spin glass, or the like. Specific examples include Cu, Au, Ag, a paramagnetic alloy containing these and a magnetic element, Pd, Pt, and an alloy containing these as a main component. Here, it is preferable that the thickness of the nonmagnetic intermediate layer 3 is set in a range of about 2 to 5 nm. If the thickness of the non-magnetic intermediate layer 3 exceeds 2 nm, it is not possible to obtain a sufficient resistance change sensitivity, and if it is less than 5 nm, it becomes difficult to sufficiently reduce the exchange coupling between the magnetic layers 1 and 2. .

The spin valve laminated film 7 is formed by the above-described layers.
In the MR element having such a spin valve laminated film 7, the second magnetic layer 2 is fixed in magnetization, whereas the first magnetic layer 1 is magnetized by an external magnetic field. Because of the reversal, the relative angles of the magnetization directions of the two magnetic layers 1 and 2 disposed with the nonmagnetic intermediate layer 3 interposed therebetween change, and a magnetoresistance effect is obtained.

In the MR element of the above embodiment, the first
Since the atomic diffusion barrier layer 5 made of oxide, nitride, carbide, boride, fluoride or the like is formed at the interface between the magnetic layer 1 and the metal buffer layer 4, When an annealing process for improving the property is performed, the interdiffusion of atoms between the first magnetic layer 1 and the metal buffer layer 4 can be suppressed stably. Also, by setting the average thickness of the atomic diffusion barrier layer 5 to 2 nm or less,
The effect of improving the film quality by the metal buffer layer 4 can be sufficiently obtained. As described above, according to the MR element of the above embodiment, the effect of improving the film quality by the metal buffer layer 4 can be sufficiently obtained, and the deterioration of the magnetoresistance effect due to heat diffusion can be suppressed. It is possible to improve the thermal stability.

Next, an embodiment for implementing the second magnetoresistance effect element (MR element) of the present invention will be described.

FIG. 2 is a cross-sectional view showing the structure of a main part of an embodiment of the second MR element. In FIG. 2, 1 is a first magnetic layer, 2 is a second magnetic layer, and a non-magnetic intermediate layer 3 is interposed between the first and second magnetic layers 1 and 2. There is no antiferromagnetic coupling between these magnetic layers 1 and 2,
It constitutes a non-bonded laminated film.

Of these magnetic layers 1 and 2, the first magnetic layer 1 comprises a ferromagnetic layer 11 made of a ferromagnetic material as described in the first embodiment and a magnetic underlayer 12 made of various soft magnetic materials.
And a laminated film of Among these, the ferromagnetic layer 11 is a layer that contributes to the magnetoresistance effect, and the magnetic underlayer 12 is a layer that improves the soft magnetic characteristics of the ferromagnetic layer 11. Here, among the above-described ferromagnetic materials, particularly, ferromagnetic materials containing Co, such as Co and a Co-based magnetic alloy, are difficult to realize good soft magnetic characteristics by themselves, so that the magnetic underlayer 12 Is a particularly desirable material.

The magnetic underlayer 12 may be composed of a soft magnetic material film composed of one kind of soft magnetic material, or may be composed of a soft magnetic material laminated film composed of two or more kinds of soft magnetic material films. Good. The constituent material of the magnetic underlayer 12 is NiF
e alloy, NiFeCo alloy, these soft magnetic alloys with Ti,
V, Cr, Mn, Zn, Nb, Mo, Tc, Hf, T
Examples of such alloys include alloys having increased resistance by adding additional elements such as a, W, and Re, and alloys having been made amorphous by adding similar additional elements to Co, such as an amorphous CoNbZr alloy.

The first magnetic layer 1 composed of a laminated film of the ferromagnetic layer 11 and the magnetic underlayer 12 is arranged so that the ferromagnetic layer 11 is in contact with the non-magnetic intermediate layer 3. Note that the arrangement is not necessarily limited to this arrangement, but it is desirable to adopt the above arrangement in order to obtain a large MR change amount. It is desirable that the ferromagnetic layer 11 and the magnetic underlayer 12 be directly magnetically exchange-coupled, and that the magnetization behaves integrally when viewed in the film thickness direction. The first magnetic layer 1 is a magnetic layer whose magnetization is reversed by an external magnetic field such as a signal magnetic field, that is, a so-called free magnetic layer.

At the interface between the ferromagnetic layer 11 and the magnetic underlayer 12 in the first magnetic layer 1, an atomic diffusion barrier layer 5 is formed. Thermal diffusion between the magnetic underlayer 12 and the magnetic underlayer 12 is suppressed. That is, by forming the atomic diffusion barrier layer 5, it is possible to suppress the deterioration of the magnetoresistance effect due to thermal diffusion, and the thermal stability of the MR element is improved.
The atomic diffusion barrier layer 5 is thermally stable and it is necessary to suppress the interdiffusion between the ferromagnetic layer 11 and the magnetic underlayer 12. Since the magnetic coupling with T.12 is broken, it is desirable to reduce the thickness as long as the effect of suppressing the mutual diffusion of atoms is not adversely affected. For this reason, the thickness of the atomic diffusion barrier layer 5 is set to an average thickness of 2 nm or less. However, if it is too thin, its function as an atomic diffusion barrier will be impaired.
The average thickness is preferably 0.5 nm or more.

The constituent material of the atom diffusion barrier layer 5 is as described in the first embodiment. As in the first embodiment, a self-oxide film which is particularly easy to form and has an excellent function of suppressing the diffusion of atoms. , A surface oxide film, a passivation film and the like are preferably used. The method for forming such an atom diffusion barrier layer 5 is also the same as described in the first embodiment.

The compound constituting the atomic diffusion barrier layer 5 does not need to have a stoichiometrically accurate composition, does not need to form a clean crystal lattice, and may be in an amorphous state. Further, the form of the atom diffusion barrier layer 5 does not have to cover the surface of the metal buffer layer 4 uniformly, but may be, for example, a state in which a pinhole is formed, the above-described oxide, nitride, carbide, and borane. monster,
It may be formed in a discontinuous state, such as a state in which fluorides and the like exist in an island shape. By forming the layers in a discontinuous state, the effect of improving the film quality of the ferromagnetic layer 11 and the magnetic coupling of the first magnetic layer 1 can be obtained better than in the case where the layers are formed continuously.

In particular, in order to sufficiently maintain the magnetic coupling between the ferromagnetic layer 11 and the magnetic underlayer 12, the area covered by the compound as described above is positively reduced and the atomic diffusion barrier layer 5 is formed. Is preferably formed in a discontinuous state. In order to sufficiently maintain the magnetic coupling between the ferromagnetic layer 11 and the magnetic underlayer 12, it is preferable that the atom diffusion barrier layer 5 is formed of a ferromagnetic material or an antiferromagnetic material. The ferromagnetic material constituting the atomic diffusion barrier layer 5 includes spinel ferrite,
Fe _x N and the like, and NiO, Mn _x
N, CoO and the like are exemplified.

The second magnetic layer 2 is a so-called pinned magnetic layer in which a bias magnetic field is applied by the antiferromagnetic layer 6 or the hard magnetic layer and magnetization is fixed, as in the first embodiment. is there. The configurations of the second magnetic layer 2 and the antiferromagnetic layer 6 are the same as in the first embodiment described above, and the same applies to the nonmagnetic intermediate layer 3.

The first magnetic layer 1 and the second magnetic layer 2 are subjected to orthogonal annealing, annealing for improving crystallinity, and the like, as in the first embodiment. The conditions for these annealing processes are as described in the first embodiment.

The spin valve laminated film 1 is composed of the above-described layers.
3 and the spin valve laminated film 1
In the MR element having the third magnetic layer 3, the second magnetic layer 2 is fixed in magnetization, while the first magnetic layer 1 is reversed in magnetization by an external magnetic field. The relative angle between the magnetization directions of the two magnetic layers 1 and 2 is changed, and a magnetoresistance effect is obtained.

In the MR element of the above embodiment, the atomic diffusion barrier layer 5 made of oxide, nitride, carbide, boride, fluoride, etc. is formed at the interface between the ferromagnetic layer 11 and the magnetic underlayer 12. Therefore, when performing the above-described orthogonal annealing or annealing treatment for improving crystallinity,
Atomic interdiffusion between the ferromagnetic layer 11 and the magnetic underlayer 12 can be stably suppressed. Also, by setting the average thickness of the atomic diffusion barrier layer 5 to 2 nm or less, the magnetic coupling between the ferromagnetic layer 11 and the magnetic underlayer 12 is not impaired. The soft magnetizing effect of the layer 11 can be favorably obtained. in this way,
According to the MR element of the above embodiment, the softening effect of the ferromagnetic layer 11 by the magnetic underlayer 12 can be sufficiently obtained, and the deterioration of the magnetoresistance effect due to thermal diffusion can be suppressed. After achieving this, it is possible to improve the thermal stability.

A pair of lead electrodes for supplying a sense current to the magnetoresistive element of the present invention is formed. The structure of the lead electrode and the method of connecting to the magnetoresistive element can be realized by applying any of a number of known techniques according to the magnetoresistive effect to be used.

For example, in a spin valve GMR element mainly using spin-dependent scattering at an interface between a pinned magnetic layer, a free magnetic layer, and a nonmagnetic intermediate layer sandwiched between them,
The pair of lead electrodes are electrically connected to both side ends of the magnetoresistive element of the present invention. The sense current flows in a direction perpendicular to the film surface such as the non-magnetic intermediate layer. For example, when using the magnetoresistance effect by a ferromagnetic tunnel junction,
A tunnel current is caused to flow in parallel with the film surface direction, and the amount of the tunnel current, voltage fluctuation, and the like are detected. Therefore, a pair of lead electrodes is connected and formed so that a sense current flows in the film surface direction. For example, a pair of lead electrodes are formed on the lower surface of the magnetoresistive element, respectively. Alternatively, one of the lead electrodes may be connected to one of the upper surface and the lower surface of the magnetoresistive element, and the other may be connected to the end of the magnetoresistive element.

Further, a lead electrode and a hard magnetic film may be laminated and used. This hard magnetic film applies a longitudinal bias to the free magnetic layer in order to suppress the generation of magnetic domains in the free magnetic layer. Therefore, an abutt system in which the hard magnetic film is formed at least on both sides of the free magnetic layer and a system in which the end portion of the free magnetic layer is laminated on the hard magnetic film are applicable.

The magnetoresistive element of the present invention is used, for example, as a GMR element of a reproducing MR head of a magnetic recording / reproducing apparatus. In addition, the magnetoresistive effect element of the present invention is GMR
It can be used for a reproducing head and formed integrally with a magnetic recording head. Further, the magnetoresistance effect element of the present invention is not limited to a magnetic head, but can be used for a magnetic storage device such as an MRAM.

The magnetic recording head has at least a pair of magnetic poles, a magnetic gap sandwiched between the pair of magnetic poles on the medium facing surface, and a recording coil for supplying a current magnetic field to the pair of magnetic poles. The GMR head and the magnetic recording head are sequentially formed on the substrate. In a separate read / write magnetic head, at least one magnetic pole of the magnetic recording head can be used as a shield layer of the read head. In the recording / reproducing integrated magnetic head, the magnetic pole of the recording head can be used as a reproducing yoke for inducing a medium magnetic field in the magnetoresistive element of the present invention. At this time, the magnetoresistive element and the reproducing yoke can be magnetically coupled. These head structures can be realized using a known technique.

FIG. 3 is a view showing an example of the structure of a read / write separated magnetic head in which the GMR element of the above-described embodiment is applied to a read head. In FIG. 3, 21 is a substrate,
As the substrate 21, Al ₂ O ₃ having an Al ₂ O ₃ layer
-A TiC substrate or the like is used. On the main surface of such a substrate 21, a lower magnetic shield layer 22 made of a soft magnetic material such as a NiFe alloy, a FeSiAl alloy, or an amorphous CoZrNb alloy is formed. On the lower magnetic shield layer 22, a GMR film 24 such as the spin valve laminated film shown in the above-described embodiment is formed via a lower reproducing magnetic gap 23 made of a nonmagnetic insulating material such as AlO _x. I have.

GMR film 24 and lower reproducing magnetic gap 23
A pair of bias magnetic field applying films 25 for applying a bias magnetic field to the GMR film 24 are disposed between the magnetic field detecting portions of the GMR film 24, that is, outside both ends of the reproduction track. Further, on the GMR film 24, Cu, Au, Zr, T
A pair of electrodes 26 made of a or the like is formed, and a sense current is supplied to the GMR film 24 by the pair of electrodes 26. The GMR film 24, the pair of bias magnetic field applying films 25 and the pair of electrodes 26 constitute a GMR element unit 27.

On the GMR element portion 27, an upper reproducing magnetic gap 28 made of the same nonmagnetic insulating material as the lower reproducing magnetic gap 23, and an upper soft magnetic material similar to the lower magnetic shield layer 22 are formed. A magnetic shield layer 29 is formed, and these constitute a shield type GMR head 30 as a reproducing head.

On the shield type GMR head 30, a thin film magnetic head 31 is formed as a recording head.
The lower write pole of the thin-film magnetic head 31 is formed of the same magnetic layer as the upper magnetic shield layer 29. That is, the upper magnetic shield layer 2 of the shield type MR head 30
Reference numeral 9 also serves as a lower recording magnetic pole of the thin-film magnetic head 31. The lower recording magnetic pole 29 also serving as the upper magnetic shield layer
A recording magnetic gap 32 made of a non-magnetic insulating material such as AlO _x and an upper recording magnetic pole 33 are sequentially formed on the upper side.
A thin-film magnetic head 21 is configured as a recording head.

FIG. 4 is a diagram showing a structural example of an MRAM to which the GMR element of the above-described embodiment is applied. The MRAM 40 shown in FIG. 1 has a GMR film 42 formed on a substrate 41 such as a glass substrate or a Si substrate. This G
The MR film 42 is made of, for example, the spin valve laminated film shown in the above-described embodiment. A write electrode 44 is provided above the GMR film 42 via an insulating layer 43. A pair of read electrodes 46 is provided at both ends of the GMR film 42 via a shunt layer 45 made of Au or the like. Thus, the MRAM 40 is configured.

[0055]

Next, specific examples of the present invention will be described.

Example 1 An amorphous CoNbZr alloy film having a thickness of 10 nm and a NiFe alloy film having a thickness of 2 nm were sequentially formed as a magnetic underlayer 12 on a thermally oxidized Si substrate by sputtering. Here, the NiFe alloy film doubles as the metal buffer layer 4.

After forming the NiFe alloy film, the surface was once exposed to the air, and a passivation film was formed on the NiFe alloy film as an atomic diffusion barrier layer. When the state of the passivation film was examined by a cross-sectional TEM, the average thickness was about 1 nm.
And the state of formation was island-like discontinuous.

Next, NiFe with a passivation film formed on the surface
On the alloy film, a 3 nm-thick Co ₉₀ F
e ₁₀ alloy film, 3 nm thick Cu film as non-magnetic intermediate layer 3,
A 3 nm-thick Co ₉₀ Fe ₁₀ alloy film as the second magnetic layer 2,
A 10 nm thick IrMn alloy film as the antiferromagnetic layer 6 and a 5 nm thick Ta film as the protective layer were sequentially laminated to produce a spin valve laminated film 13 (7).

On the other hand, as Comparative Example 1 with the present invention, NiF
After forming the e-alloy film, without exposing its surface to the atmosphere, except that all layers are continuously formed in a vacuum chamber,
A spin valve laminated film was manufactured in the same manner as in Example 1 above. In the spin valve laminated film of Comparative Example 1, NiFe
No atomic diffusion barrier layer is formed at the interface between the alloy film and the Co ₉₀ Fe ₁₀ alloy film.

After patterning each of the spin valve laminated films according to Example 1 and Comparative Example 1 described above, 52
Annealed at 3K. The MR change rate of each MR element thus obtained was measured. The MR change rates were measured after annealing for 2 hours, after annealing for 10 hours, after annealing for 50 hours, and after annealing for 100 hours, respectively. From these measurement results, the thermal properties of the MR element according to the example and the MR element according to the comparative example were measured. The stability was compared. MR after each annealing time
Table 1 shows the measurement results of the rate of change.

[0061]

[Table 1] As can be seen from Table 1, the NiFe alloy film /
In Comparative Example 1 in which the atomic diffusion barrier layer was not formed at the interface of the Co ₉₀ Fe ₁₀ alloy film, the MR change rate immediately after film formation was relatively good at 6.9%, but the MR change rate sharply increased after annealing for 2 hours. Has decreased. Then, the MR ratio continued to decrease with the lapse of annealing time, and after 100 hours of annealing, the MR ratio decreased to 4.9%. This is thought to be due to the fact that there was no barrier layer for suppressing atomic diffusion at the interface of the NiFe alloy film / Co ₉₀ Fe ₁₀ alloy film, and the inter-diffusion of atoms progressed by annealing, thereby reducing the MR change rate. Can be Thus, Comparative Example 1
Was low in thermal stability (heat resistance).

On the other hand, in Example 1 in which the atomic diffusion barrier layer was formed at the interface between the NiFe alloy film and the Co ₉₀ Fe ₁₀ alloy film by exposing it to the air after the formation of the NiFe alloy film, the characteristics immediately after the film formation were different from those of Comparative Example 1. Although low, the MR ratio increased to 8.0% after 2 hours of annealing. This is because the crystallinity of each layer is improved by annealing for 2 hours and NiF
It is considered that this is because the atomic diffusion at the interface between the e alloy film and the Co ₉₀ Fe ₁₀ alloy film was suppressed by the atomic diffusion barrier layer.
Furthermore, the MR change rate is 8.
It can be seen that the atomic diffusion at the interface between the NiFe alloy film and the Co ₉₀ Fe ₁₀ alloy film was suppressed from 0%. Thus, the MR element of Example 1 was excellent in thermal stability (heat resistance).

Example 2 A 10 nm-thick amorphous CoNb film was first formed as a magnetic underlayer 12 on a thermally oxidized Si substrate by plasma sputtering.
A Zr alloy film and a 2 nm-thick NiFe alloy film were sequentially formed. Here, the NiFe alloy film doubles as the metal buffer layer 4.

After the NiFe alloy film was formed, the plasma was once stopped, argon gas containing 20% oxygen was introduced into the vacuum chamber, and an oxide film was formed as an atomic diffusion barrier layer on the surface of the NiFe alloy film. At this time, the thickness of the surface oxide film was variously changed by controlling the introduction pressure and time of the mixed gas of oxygen and argon. The average thickness of the obtained surface oxide film is as shown in Table 2 below. In Comparative Example 2 in the table, the thickness of the surface oxide film was out of the range of the present invention.

[0065]

[Table 2] The thickness of the surface oxide film shown in Table 2 is an average thickness, and the oxide film having that thickness is not necessarily formed uniformly. Therefore, in the sample No. 1 of Example 2 in which the average thickness of the surface oxide film was 0.3 nm, relatively many pinholes were present in the surface oxide film.

Next, on each NiFe alloy film on which the surface oxide film was formed, a 3 nm-thick C
o ₉₀ Fe ₁₀ alloy film, 3 nm thick C as the nonmagnetic intermediate layer 3
u film, a 2 nm thick Co ₉₀ Fe ₁₀ alloy film as the second magnetic layer 2, an 8 nm thick IrMn alloy film as the antiferromagnetic layer 6,
As a protective layer, a Ta film having a thickness of 5 nm was sequentially laminated to form a spin valve laminated film 13 (7).

After patterning each of the spin valve laminated films according to Example 2 and Comparative Example 2 described above, 52
Annealed at 3K for 2 hours. Each M thus obtained
The MR ratio of the R element was measured immediately after film formation and after annealing for 2 hours. Table 3 shows the measurement results.

[0068]

[Table 3] In each of the MR elements according to Example 2, the MR ratio increased after annealing for 2 hours, and the effect of the atomic diffusion barrier layer composed of the surface oxide film was confirmed. However, in the sample with a thin surface oxide film, the MR change rate did not increase so much, and it is presumed that slight atomic interdiffusion occurred. , A good MR change rate is obtained.

On the other hand, in the MR element according to Comparative Example 2, although the MR ratio slightly increased after annealing for 2 hours,
Since the MR ratio at the beginning (immediately after film formation) is small, a sufficient MR ratio cannot be obtained as a result. This is presumably because the thickness of the surface oxide film was too large, so that the effects of the magnetic underlayer and the metal buffer layer could not be obtained. Further, fcc orientation can not be sufficiently obtained, since the expired further magnetic coupling between the magnetic base layer, the coercive force H _c soft magnetic characteristics is deteriorated were 3 Oe.

[0070]

As described above, according to the present invention, heat diffusion between the metal buffer layer and the magnetic layer or between the magnetic underlayer and the ferromagnetic layer can be suppressed, so that high performance and thermal stability can be obtained. An excellent magnetoresistive element can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a main structure of an embodiment of a first magnetoresistive element of the present invention.

FIG. 2 is a cross-sectional view illustrating a main structure of an embodiment of a second magnetoresistive element of the present invention.

FIG. 3 is a cross-sectional view showing one configuration example of a read / write separated magnetic head using the magnetoresistive element of the present invention.

FIG. 4 is an MRA using the magnetoresistance effect element of the present invention.
FIG. 3 is a cross-sectional view illustrating a configuration example of M.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st magnetic layer 2 ... 2nd magnetic layer 3 ... Non-magnetic intermediate layer 4 ... Metal buffer layer 5 ... Atomic diffusion barrier layer 7, 13 ... Spin valve film 11 ... Ferromagnetic layer 12 ... magnetic underlayer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideaki Fukuzawa 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Kawasaki Office (72) Inventor Hitoshi Iwasaki 72 Horikawa-cho, Sachi-ku, Kawasaki-shi, Kanagawa Toshiba Corporation Inside the Kawasaki Office (72) Inventor Masashi Sabashi 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Inside the Higashi-Shiba Kawasaki Office

Claims (8)

[Claims] 1. A first magnetic layer formed on a metal buffer layer, a second magnetic layer, and a non-magnetic intermediate layer disposed between the first magnetic layer and the second magnetic layer. A magnetoresistive effect element comprising a spin valve film having an atomic diffusion barrier layer having an average thickness of 2 nm or less at an interface between the metal buffer layer and the first magnetic layer. Magnetoresistive element. 2. A first magnetic layer made of a ferromagnetic material containing Co and formed on a metal buffer layer having an fcc crystal structure, a second magnetic layer, the first magnetic layer and the second magnetic layer. A magnetoresistive element including a spin valve film having a nonmagnetic intermediate layer disposed between the magnetic layer and a magnetic layer, wherein an oxide, a nitride, and a carbide are provided at an interface between the metal buffer layer and the first magnetic layer. A magnetoresistive element comprising an atomic diffusion barrier layer containing at least one selected from borides and fluorides as a main component. 3. The magnetoresistive element according to claim 2, wherein the atomic diffusion barrier layer has an average thickness of 2 nm or less. 4. A first magnetic layer composed of a laminated film of a magnetic underlayer and a ferromagnetic material layer, a second magnetic layer, and disposed between the first magnetic layer and the second magnetic layer. A magnetoresistive effect element including a spin valve film having a non-magnetic intermediate layer formed thereon, wherein an average thickness of 2 nm is provided at an interface between the magnetic underlayer and the ferromagnetic layer.
A magnetoresistive element having an atomic diffusion barrier layer of nm or less. 5. A method according to claim 1, wherein the first magnetic layer comprises a laminated film of a magnetic underlayer and a ferromagnetic layer containing Co, a second magnetic layer, and the first magnetic layer and the second magnetic layer. A magnetoresistive element including a spin valve film having a non-magnetic intermediate layer disposed therebetween, comprising: an oxide, a nitride, a carbide, a boride, and a fluoride at an interface between the magnetic underlayer and the ferromagnetic layer. A magnetoresistive element comprising an atomic diffusion barrier layer containing at least one element selected from oxides as a main component. 6. The magnetoresistive element according to claim 5, wherein the atomic diffusion barrier layer has an average thickness of 2 nm or less. 7. The magnetoresistance effect element according to claim 1, wherein a pinhole is formed in said atomic diffusion barrier layer. element. 8. The magnetoresistive element according to claim 1, wherein the atomic diffusion barrier layer is made of a ferromagnetic material or an antiferromagnetic material. Magnetoresistive element.