JPH0963021A - Magneto-resistive effect element having spin valve structure and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an MR element which stably exhibits a high magneto- resistive effect by laminating an antiferromagnetic layer consisting of an NiMn alloy, a first ferromagnetic layer, a non-magnetic layer and a second ferromagnetic layer in this order from a substrate side on a substrate. SOLUTION: A ground surface layer 11 is formed on the substrate and the antiferromagnetic layer 12 consisting of the NiMn alloy, the first ferromagnetic layer 13, the non-magnetic layer 14, the second ferromagnetic layer 15 and a protective layer 16 for preventing oxidation are laminated in this order on the substrate. The magnetization direction a1 of the first ferromagnetic layer 13 is subjected peening by the antiferromagnetic layer 12. On the other hand, the direction b2 of the magnetization of the second ferromagnetic layer 15 is freely rotated by the magnetic field impressed from outside, by which the high-sensitivity magneto-resistive effect is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive reproducing head used in a magnetic disk device, and more particularly to a magnetoresistive effect element having a magnetic multilayer film known as a spin valve structure and a method for manufacturing the same.

[0002]

2. Description of the Related Art A magnetoresistive (MR) type reproducing head utilizing a magnetoresistive effect has attracted attention because a reproducing output can obtain a high output without depending on the speed of a recording medium.

Conventionally, magnetic thin films of NiFe alloy and NiCo alloy have been used as MR elements. However, in recent years, with the demand for higher output of the head, a magnetic multilayer film having a high magnetoresistive effect, which is formed by laminating a magnetic layer and a non-magnetic layer, has been attracting attention as an MR element.

For example, the magnetoresistance change rate of a NiFe alloy thin film is set to about 2%, on the other hand, NiFe thin films and Co thin films are alternately laminated to form Cu between each laminated magnetic layer.
In the case of a magnetic multi-layer film having a thin film layer interposed, it is 10 at room temperature.
%, It is known that a large magnetoresistive effect can be obtained (Journal of Magnetisman).
d Magnetic Materials, Vol. 99,
243-252, 1991). In addition to this, for example, a magnetic multilayer film in which NiFe thin films and Cu thin films are alternately laminated has a magnetoresistive change rate of 16% or more at room temperature of about 600.
It is known to show in an externally applied magnetic field of Oe (Applied Physics Letters,
60, 512-514, 1992).

Among the magnetic multi-layered films, the spin valve film has attracted the most attention due to its high magnetic field sensitivity (for example, PHYSICAL REVIEW B, 43).
Volume, 1297-1300, 1991, and Jour.
nal of Applied Physics, 69
Vol., Pp. 4774-4779, 1991, and further, JP-A-4-358310).

The basic structure of the spin valve film is a laminated structure of a ferromagnetic layer, a nonmagnetic layer, a ferromagnetic layer and an antiferromagnetic layer. The exchange bias magnetic field from the antiferromagnetic layer pin the magnetization of the magnetic layer adjacent to it, while the magnetization of the other magnetic layer rotates freely with respect to the external magnetic field. A parallel state is realized and a high magnetoresistive effect is obtained. Even in the above literature, the MR change rate of 4.1% is 1
As obtained with an externally applied magnetic field of 0 Oe, this spin valve film has a very high magnetic field sensitivity.

A general spin valve film is NiFe / C.
It has a film structure of u / NiFe (or Co) / FeMn. Here, NiFe is Ni: Fe = 81: 19 (at
%) Permalloy. Although many studies have been conducted on the type and composition of the ferromagnetic layer, the above composition is considered to be optimal in order to obtain good soft magnetic characteristics and high magnetoresistive effect. For the magnetic layer in which the magnetization is pinned by the antiferromagnetic layer, Co or an alloy containing Co is considered to be preferable in addition to NiFe because a large MR change rate can be obtained. The composition of FeMn used as the antiferromagnetic layer is generally Fe: Mn = 50: 50 (at%). FeMn exhibiting antiferromagnetism is γ-FeMn, and an underlayer for stable formation of FeMn has been studied. For example, Ja
panese Journal of Applied
Physics, 33, 133-137, 199.
It has been reported in 4 years that a metal or alloy film having an fcc structure may be formed on a metal such as Ta, Hf, or Ti.

The FeMn alloy film has problems that it has poor corrosion resistance, the blocking temperature is not sufficiently high, and the exchange bias magnetic field has a large temperature dependency. Therefore, Fe
An antiferromagnetic layer replacing Mn has also been studied. NiM
Although n has a large exchange bias magnetic field and a large blocking temperature and is excellent in corrosion resistance, it does not exhibit antiferromagnetism unless subjected to heat treatment at a high temperature for a long time (Applied).
Physics Letters, Volume 65, 1183-
1185, 1994).

An example in which NiMn is actually used as an antiferromagnetic layer of a spin valve is reported in the abstract of the spring meeting of the Japan Institute of Metals, page 362, 1995, but there is no description about MR characteristics and the structure is NiFe / Cu / NiFe
/ NiMn only. As another antiferromagnetic layer, oxides such as NiO have been investigated, and are disclosed in Japanese Patent Laid-Open No.
The characteristics are reported in Japanese Patent No. 347013.

[0010]

As described above, when the antiferromagnetic layer made of NiMn, which is excellent in corrosion resistance and has a sufficiently high blocking temperature and a small temperature dependence of the exchange bias magnetic field, the following is used. Inconvenience occurs. That is,
In order to obtain good antiferromagnetism with NiMn, it is necessary to perform heat treatment in a magnetic field at high temperature for a long time to form a θ phase. The basic structure of the conventional spin valve film is a ferromagnetic layer, a non-magnetic layer,
Since it has a laminated structure of a ferromagnetic layer and an antiferromagnetic layer, if heat treatment is performed in a magnetic field for a long time after the antiferromagnetic layer is formed (after all the films forming the spin valve are formed), it becomes Ni. Since Cu is a solid solution system, mutual diffusion occurs at the interface between the nonmagnetic layer and the second ferromagnetic layer, and the rate of change in magnetoresistance decreases.

Therefore, it is an object of the present invention to provide an MR element stably exhibiting a high magnetoresistive effect and a method for manufacturing the MR element.

Another object of the present invention is to provide an MR element having a large rate of change in magnetoresistance and a method for manufacturing the MR element.

Still another object of the present invention is to provide an MR element having a large exchange bias magnetic field from the antiferromagnetic layer and a method for manufacturing the MR element.

Still another object of the present invention is to provide an MR element having a high blocking temperature of the antiferromagnetic layer, a small temperature dependence of the exchange bias magnetic field, and a good corrosion resistance, and a manufacturing method thereof.

[0015]

In order to achieve the above object, according to the present invention, at least NiMn is formed on a substrate.
There is provided an MR element having a spin valve structure in which an antiferromagnetic layer made of an alloy, a first ferromagnetic layer, a nonmagnetic layer and a second ferromagnetic layer are stacked in this order from the substrate side.

Further, according to the present invention, at least the first antiferromagnetic layer made of the NiMn alloy film and the first antiferromagnetic layer are formed on the substrate.
A ferromagnetic layer, a first non-magnetic layer, a second ferromagnetic layer, a second non-magnetic layer, a third ferromagnetic layer and a second anti-ferromagnetic layer are laminated in this order from the substrate side. An MR element having a dual spin valve structure is provided.

Since the antiferromagnetic layer (first antiferromagnetic layer) made of a NiMn alloy is provided closer to the substrate than the nonmagnetic layer (first nonmagnetic layer) and the second ferromagnetic layer, NiM
The n-alloy layer can be formed before the nonmagnetic layer (first nonmagnetic layer) and the second ferromagnetic layer are stacked and heat-treated in a magnetic field. Therefore, even if heat treatment is performed in a magnetic field at high temperature for a long time in order to obtain good antiferromagnetism with the NiMn alloy, the non-magnetic layer (first non-magnetic layer) and the second ferromagnetic layer have an interface at the interface. There is no inconvenience that mutual diffusion occurs and the rate of change in magnetoresistance decreases. Therefore, it is possible to provide an MR element that stably exhibits a high magnetoresistive effect.

Further, since the NiMn alloy is used as the antiferromagnetic layer (first antiferromagnetic layer) without using the FeMn alloy, the exchange bias magnetic field from this antiferromagnetic layer is large, and this It is possible to obtain an MR element having a high blocking temperature of the antiferromagnetic layer and a small temperature dependence of the exchange bias magnetic field, as well as good corrosion resistance.

Even in the dual spin valve structure, NiM
By using the first antiferromagnetic layer that has obtained good antiferromagnetism by the n-alloy, it is possible to prevent the direction of the pinned magnetization from being disturbed by the magnetic field generated by the sense current. Of course, by adopting the double spin valve structure, it is possible to stably obtain a larger magnetoresistance change rate than the spin valve film having the basic structure.

It is preferable that the magnetoresistance change rate is 3% or more and the exchange bias magnetic field is 100 Oe or more.

The layer thickness of the antiferromagnetic layer (first antiferromagnetic layer) is preferably 50Å to 500Å.

It is preferable that each of the ferromagnetic layers is made of an alloy containing any one of Ni, Fe and Co, and the thickness of the first ferromagnetic layer is 15Å to 150Å.

Each of the nonmagnetic layers is made of any one of Cu, Ag and Au, and the layer thickness of the nonmagnetic layer (first nonmagnetic layer) is preferably 15Å to 50Å.

By using such materials and layer thicknesses, it is possible to provide an MR element having a large magnetoresistance change rate.

Ta, Hf, Cr, N are formed on the bottom layer of the substrate.
It is also preferable to have an underlayer made of any one metal of b, Zr and Ti.

In particular, by using an appropriate underlayer in the double spin valve structure, it is possible to stably obtain a larger magnetoresistance change rate than that of the spin valve film having the basic structure, and the resistance value between the electrodes is increased. Can be lowered. Furthermore, the use of a suitable underlayer in the dual spin valve structure also prevents the magnetic field created by the sense current from disturbing the orientation of the pinned magnetization.

According to the present invention, the method further includes a film forming step of laminating thin films on the substrate and a heat treating step of heat treating the laminated substrates in a magnetic field. A step of sequentially laminating an antiferromagnetic layer, a first ferromagnetic layer, a nonmagnetic layer and a second ferromagnetic layer
Provided is a method of manufacturing an MR element having a spin valve structure, which comprises performing a heat treatment step before stacking a nonmagnetic layer and a second ferromagnetic layer.

According to the invention, still further on the substrate:
A first antiferromagnetic layer and a first ferromagnetic layer made of at least a NiMn alloy, including a film forming step of forming a thin film in a laminated film and a heat treatment step of heat-treating the laminated substrate in a magnetic field. The first nonmagnetic layer, the second ferromagnetic layer, the second nonmagnetic layer, the third ferromagnetic layer, and the second antiferromagnetic layer are sequentially stacked, and the heat treatment step includes There is provided a method of manufacturing a magnetoresistive effect element having a spin valve structure, which is performed before the nonmagnetic layer and the second ferromagnetic layer are stacked.

The heat treatment step described above is a step of forming the θ phase of NiMn, and is preferably performed before or after the step of laminating the first ferromagnetic layer.

As described above, the NiMn alloy layer is formed before the nonmagnetic layer (first nonmagnetic layer) and the second ferromagnetic layer are laminated and heat-treated in a magnetic field. Even if heat treatment is performed in a magnetic field at high temperature for a long time to obtain magnetism, mutual diffusion occurs at the interface between the non-magnetic layer (first non-magnetic layer) and the second ferromagnetic layer, resulting in a magnetoresistance change rate. There is no inconvenience. Therefore, it is possible to provide an MR element that stably exhibits a high magnetoresistive effect.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

FIG. 1 is a perspective sectional view of an embodiment of the MR element according to the present invention. In the figure, reference numeral 11 denotes an underlayer formed on the substrate, on which the antiferromagnetic layer 1 is formed.
2, the first ferromagnetic layer 13, the non-magnetic layer 14, the second ferromagnetic layer 15, and the protective layer 16 for preventing oxidation are sequentially laminated in this order.

The principle of the magnetoresistive effect of the spin valve film is as follows.
When the magnetization directions of the first and second ferromagnetic layers deviate from each other, conduction electrons are scattered to increase the resistance, and the magnetization directions of both magnetic layers are opposite to each other. When it becomes, it is to show the maximum resistance. In the spin valve film in the embodiment of FIG. 1, the magnetization direction a _{1 of} the first ferromagnetic layer 13 is pinned by the antiferromagnetic layer 12, while the magnetization direction b _{1 of} the second ferromagnetic layer 15 is pinned.
Is freely rotated by a magnetic field applied from the outside, a highly sensitive magnetoresistive effect can be obtained.

[0034] Figure 1 is further illustrated and direction e ₁ direction d ₁ and the sense current of an externally applied magnetic field is. The pinned magnetization direction a ₁ and the externally applied magnetic field direction d ₁ are parallel to each other, and the direction e is orthogonal to this direction.
Sense current flows to ₁ . The easy axis of magnetization of the second ferromagnetic layer 15 is orthogonal to the direction d ₁ of the externally applied magnetic field. This is because the coercive force is reduced by reversing the magnetization in the direction of the hard axis, and the characteristic of good linearity in the magnetoresistance change curve is obtained. This also reduces noise when used as an MR element of an MR head. By the way, the magnetic resistance change curve is one in which the vertical axis is the magnetic resistance change rate and the horizontal axis is the externally applied magnetic field. Here, the rate of change in magnetic resistance is represented by Δρ / ρs, where ρs is the minimum specific resistance and Δρ is the change in specific resistance relative to that.

In the material forming the spin valve film in this embodiment, the antiferromagnetic layer 12 is made of NiMn, and the first and second materials are used.
The ferromagnetic layers 13 and 15 are alloys containing any one of Ni, Fe and Co, and the non-magnetic layer 14 is Cu, Ag and Au.
Is any one of The composition of NiMn is Ni: Mn =
50:50 (at%) is preferable, and N is particularly preferable.
i: Mn = 44: 56 (at%). As the first ferromagnetic layer 13, Co or an alloy containing Co is particularly preferable in order to obtain a larger magnetoresistance change rate. Further, Cu is preferable for the non-magnetic layer 14. The second ferromagnetic layer 15 is preferably a film having good soft magnetic characteristics, and particularly N
Permalloy of i: Fe = 81: 19 (at%) is preferable.

The reason why NiMn is used for the antiferromagnetic layer 12 is that the blocking temperature is high, the exchange bias magnetic field is large, and the corrosion resistance is good. However, N
In order to obtain good antiferromagnetism with iMn, it is necessary to perform heat treatment in a magnetic field at high temperature for a long time to form a θ phase. When heat treatment is performed in a magnetic field for a long time after forming all the films constituting the spin valve, Ni and Cu are solid solutions, so that interdiffusion occurs at the interface between the nonmagnetic layer 14 and the second ferromagnetic layer 15. Occurs, and the rate of change in magnetic resistance decreases.

Therefore, in this embodiment, after the NiMn layer 12 and the first ferromagnetic layer 13 are formed, heat treatment is performed in a magnetic field for a long time to form a θ phase exhibiting antiferromagnetism, and then the surface is etched. After exposing the clean surface of the first ferromagnetic layer 13,
The remaining spin valve constituent film is formed. The layer thickness of the first ferromagnetic layer 13 before heat treatment and the layer thickness to be milled and cut are appropriately selected with respect to the final first ferromagnetic layer thickness.

That is, as shown in FIG. 2, first, the underlayer 11 is formed on the substrate (step S20). Underlayer 11
As the film, a film in which Ta and NiFe are laminated is used.
Ta is used to smooth the interface, and NiFe having an fcc structure is used to facilitate formation of the fct structure by NiMn. As the underlayer 11, other than that, Hf, Cr, N
It may be any one metal of b, Zr and Ti. Then, an antiferromagnetic layer 12 made of NiMn is formed thereon.
And the first ferromagnetic layer 13 are stacked (steps S21 and S22). Next, this laminated body is heat-treated at a high temperature for a long time in a magnetic field to form a θ phase of a NiMn alloy (step S23). Next, the nonmagnetic layer 14 is stacked (step S24), and the second ferromagnetic layer 15 is stacked (step S2).
5), and stacking the protective layer 16 for oxidation prevention (step S
26) is performed to obtain an MR element.

The above-mentioned heat treatment process in a magnetic field is performed using NiMn.
After the formation of the antiferromagnetic layer 12 by the method described above, it may be performed before the first ferromagnetic layer 13 is laminated. For example, as shown in FIG. 3, first, the base layer 11 is formed on the substrate (step S30). Then, the antiferromagnetic layer 12 made of NiMn is stacked thereon (step S31). Then, this laminate is subjected to a heat treatment in a magnetic field at high temperature for a long time, and NiM
The θ phase of the n alloy is formed (step S32). Then
Lamination of the first ferromagnetic layer 13 (step S33), lamination of the non-magnetic layer 14 (step S34), second ferromagnetic layer 15
Layer (step S35), and protective layer 1 for preventing oxidation
The MR element is obtained by stacking 6 (step S36).

FIG. 4 shows a perspective sectional view of another embodiment of the MR element according to the present invention. In the figure, reference numeral 41 denotes an underlayer formed on the substrate, on which the first antiferromagnetic layer 42, the first ferromagnetic layer 43, and the first nonmagnetic layer 4 are formed.
4, the second ferromagnetic layer 45, the second nonmagnetic layer 46, the third ferromagnetic layer 47, the second antiferromagnetic layer 48, and the protective layer 49 for preventing oxidation were sequentially stacked in this order. It has a structure. That is, in this embodiment, the MR element has a double spin valve structure.

The magnetization directions a ₂ and c ₂ of the first and third ferromagnetic layers 43 and 47 are pinned by the first and second antiferromagnetic layers 42 and 48, respectively, and the magnetization directions of the second ferromagnetic layer 45 are The magnetization direction b ₂ is freely reversed by the external magnetic field, and the magnetoresistive effect is obtained. This second ferromagnetic layer 45
Since both interfaces contribute to the magnetoresistance change, the magnetoresistance effect is larger in the double spin valve structure than in the spin valve film having the basic structure.

The direction d _{2 of the} magnetic field applied from the outside and the direction e _{2 of the} sense current are as shown in FIG. 4, and the relationship is the same as in the embodiment of FIG.

The first, second and third ferromagnetic layers 43, 45
An alloy containing any one of Ni, Fe and Co can be used as and 47, but a good soft magnetic property is required for the second ferromagnetic layer 45, so that N is particularly preferable.
Permalloy of i: Fe = 81: 19 (at%) is preferable, and as the first and third ferromagnetic layers 43 and 47, Co or Co is particularly preferable in order to obtain a larger magnetoresistance change rate.
Alloys containing are preferred. As the first and second non-magnetic layers 44 and 46, any one of Cu, Ag and Au can be used, but Cu is particularly preferable.

In this double spin valve structure, NiMn is used for the first antiferromagnetic layer 42 and FeMn is used for the second antiferromagnetic layer 48. The composition of NiMn is Ni: M
n = 50: 50 (at%) is preferable.

Next, the first and second non-magnetic layers 44 and 4
Consider the effect of the magnetic field created by the sense current flowing through 6. When the size of the element is large and the current density of the sense current is small, this magnetic field can be ignored, but the shape of the MR element in the MR head has a large influence of this magnetic field. The magnetic field generated by the current flowing through the first nonmagnetic layer 44 is in the direction opposite to the magnetization direction pinned in the first ferromagnetic layer 43, while the magnetic field generated by the second nonmagnetic layer 46 is the third magnetic field. The same direction as the direction of the pinned magnetization in the ferromagnetic layer 47. Therefore, the magnetization direction of the third ferromagnetic layer 47 is stabilized, but the magnetization direction of the first ferromagnetic layer 43 is disturbed.

However, in the present embodiment, since NiMn having a large blocking temperature and a large exchange bias magnetic field is used as the first antiferromagnetic layer 42, the magnetization direction of the first ferromagnetic layer 43 should be strongly pinned. You can As described above, since NiMn needs to be heat-treated in a magnetic field at high temperature for a long time, NiMn is used only in the first antiferromagnetic layer 42. Since the magnetization direction is disturbed only in the first ferromagnetic layer 43, it is sufficiently effective to use NiMn having a large blocking temperature and a large exchange bias magnetic field only in the first antiferromagnetic layer 42. .

Also in the present embodiment, as in the case of the embodiment of FIG. 1, after the NiMn layer 42 and the first ferromagnetic layer 43 which are the first antiferromagnetic layers are formed, heat treatment is performed in a magnetic field for a long time. After forming the θ phase exhibiting antiferromagnetism, the surface is etched to expose the clean surface of the first ferromagnetic layer 43,
The remaining spin valve constituent film is formed.

That is, as shown in FIG. 5, first, the base layer 41 is formed on the substrate (step S50). Underlayer 41
As the film, a film in which Ta and NiFe are laminated is used.
Ta is used to smooth the interface, and NiFe having an fcc structure is used to facilitate formation of the fct structure by NiMn. As the base layer 41, in addition, Hf, Cr, N
It may be any one metal of b, Zr and Ti. Then, the first antiferromagnetic layer 42 and the first ferromagnetic layer 43 made of NiMn are stacked thereon (step S
51 and 52). Next, this laminated body is heat-treated at a high temperature for a long time in a magnetic field to form a θ phase of a NiMn alloy (step S53). Next, the first nonmagnetic layer 44 is stacked (step S54), the second ferromagnetic layer 45 is stacked (step S55), the second nonmagnetic layer 46 is stacked (step S56), and the third ferromagnetic layer is stacked. 47 layers (step S5)
7), stacking the second antiferromagnetic layer 48 (step S58)
And stacking a protective layer 49 for preventing oxidation (step S59)
Then, the MR element is obtained.

The above-mentioned heat treatment process in a magnetic field is performed using NiMn.
After the formation of the first antiferromagnetic layer 42 by the above, it may be performed before the formation of the first ferromagnetic layer 43. For example, as shown in FIG. 6, first, the base layer 41 is formed on the substrate (step S60). Then, the first antiferromagnetic layer 42 made of NiMn is stacked thereon (step S6).
1). Next, this laminate is heat-treated at a high temperature for a long time in a magnetic field to form a θ phase of a NiMn alloy (step S
62). Next, the first ferromagnetic layer 43 is stacked (step S63), and the first nonmagnetic layer 44 is stacked (step S6).
4), stacking the second ferromagnetic layer 45 (step S65),
Lamination of the second non-magnetic layer 46 (step S66), lamination of the third ferromagnetic layer 47 (step S67), lamination of the second antiferromagnetic layer 48 (step S68), and protective layer 49 for oxidation prevention. Are stacked (step S69) to obtain an MR element.

[0050]

EXAMPLES The present invention will be described in more detail with reference to specific examples.

Example 1 As a sample for evaluation, the basic spin valve structure shown in FIG. 1 was formed on a 3-inch glass substrate. The film formation was performed on the glass substrate using RF magnetron sputtering and ion beam sputtering. As the RF magnetron sputtering film forming conditions, the ultimate vacuum is 5 × 10 ⁻⁴ Pa or less,
During film formation, the degree of vacuum is about 4 × 10 ⁻¹ Pa, and the Ar gas flow rate is 5
The sccm and RF power were set to 500W. The deposition conditions for ion beam sputtering are such that the ultimate vacuum is 5 × 10 ⁻⁵ Pa or less, the vacuum during deposition is about 1.2 × 10 ⁻² Pa, the Ar gas flow rate is 7 sccm, and the sputter gun acceleration voltage is 300.
V and ion current were 30 mA. A magnetic field of about 100 Oe was applied during film formation.

As shown in FIG. 2, the procedure of the manufacturing process is as follows. First, by RF magnetron sputtering, NiMn as the underlayer 11 and the antiferromagnetic layer 12 is formed on the glass substrate.
A film and a Co film as the first ferromagnetic layer 13 are formed,
Once removed from the chamber. Then, it was set in a heat treatment furnace in a magnetic field and heat-treated at a high temperature of 250 ° C. or higher in a magnetic field of 3 kOe for a long time. In this example, the heat treatment was repeated three times, in which the temperature was maintained at a predetermined temperature for 5 hours and then returned to room temperature. After the heat treatment, the film was set in an ion beam sputtering apparatus, and a clean surface of Co was first exposed by milling to form a remaining spin valve constituent film starting from Co until a predetermined layer thickness was reached. The composition of NiMn in this example is Ni: Mn = 50: 50 (at%).

FIG. 7 shows the X-ray diffraction patterns of the NiMn film before and after the heat treatment. As a typical example, Ta (5
0Å) / NiMn (500Å) / Ta (50Å) was used. The peak of the fcc structure is detected before the heat treatment, but the peak of the fct structure is detected after the heat treatment, and the θ phase exhibiting antiferromagnetism is formed after the heat treatment.

The material and layer thickness (Å) of each layer of the spin valve film produced in this example, the magnetoresistance change rate (%),
Table 1 shows the exchange bias magnetic field (Oe) and the heat treatment conditions after the NiMn film was formed. Here, in Table 1, the materials constituting each sample are listed in the order of stacking from the substrate direction (m1, m2,
m3 ...), and their layer thicknesses are indicated as (t1, t2, t3 ...). That is, the materials of the base layer 11 are m1 and m2 (layer thickness t
1 and t2), the material of the antiferromagnetic layer 12 is m3 (layer thickness t
3), the material of the first ferromagnetic layer 13 is m4 (layer thickness t4),
The material of the nonmagnetic layer 14 is m5 (layer thickness t5), the material of the second ferromagnetic layer 15 is m6 (layer thickness t6), and the material of the protective layer 16 is m7 (layer thickness t7). The layer thickness design conditions are considered to be optimal for each configuration.

[0055]

[Table 1]

From the results shown in Table 1, in the samples (Sample Nos. 1 to 3) in which each layer up to the first ferromagnetic layer 13 was heat-treated at a high temperature in a magnetic field and then the remaining spin valve film was formed, It can be seen that the rate of change and the exchange bias magnetic field are obtained. 2 after forming all the constituent layers
In the sample heat-treated at 10 ° C (Sample No. 4),
Sufficient exchange bias magnetic field is not obtained. Further, in the sample (Sample No. 5) which was heat-treated at 350 ° C. after forming all the constituent layers, the Cu layer (nonmagnetic layer 14) and N
Due to diffusion with the iFe layer (second ferromagnetic layer 15),
A good rate of change in magnetoresistance has not been obtained. It should be noted that although the underlayer is not always necessary, the provision of the underlayer has the effect of increasing the exchange bias magnetic field. In FIG.
The magnetic resistance change curve of sample No. 1 in which the best magnetic resistance effect was obtained is shown.

Tables 2 to 5 show the magnetoresistance change rate (%) and the exchange bias magnetic field (Oe) when the layer thickness condition or the heat treatment condition was changed under the same layer structure as the sample number 1 in Table 1. Show.

[0058]

[Table 2]

[0059]

[Table 3]

[0060]

[Table 4]

[0061]

[Table 5]

Table 2 shows the case where the layer thickness t3 of the antiferromagnetic layer 12 (NiMn layer) is changed. In order to obtain a large exchange bias magnetic field, there is a tendency that a slightly thicker layer thickness is required than when the antiferromagnetic layer is made of FeMn. When the layer thickness t3 is too thin, a sufficient exchange bias magnetic field is not obtained and a good magnetoresistive effect is not obtained (Sample No. 6). 100 at layer thickness t3 of 50Å or more
An exchange bias magnetic field of Oe or more was obtained, and the magnetoresistance change rate was 3.0% (sample numbers 1 and 7 to
9) A sufficiently large and preferred exchange bias magnetic field has a layer thickness t
3 is obtained at about 250 Å or more (sample numbers 1 and 9). When the layer thickness t3 is further increased, the exchange bias magnetic field is gradually increased, but NiMn itself does not contribute to the magnetoresistive effect. Therefore, if the layer thickness t3 is too thick, the magnetoresistive change rate decreases (Sample No. 10). ). Therefore, it can be said that the preferable layer thickness range is up to about 500 Å where an MR change rate of 3.0% is obtained. That is, the layer thickness t3 of the antiferromagnetic layer 12 is preferably 50Å ≦ t3 ≦ 500Å (sample numbers 1 and 7 to 9).

Table 3 shows the case where the layer thickness t4 of the first ferromagnetic layer 13 (Co layer) is changed. Since the layer thickness t4 of the first ferromagnetic layer 13 is 15Å and a magnetoresistance change rate of 3.0% is obtained, the layer thickness t4 is preferably more than this (Sample No. 12). When the layer thickness t4 increases, the scattering capacity of conduction electrons increases and the magnetoresistance change rate increases in the range up to about 60 Å (sample numbers 1 and 12 to 14). However, as the layer thickness t4 increases, the exchange bias magnetic field received decreases and pinning becomes insufficient. Therefore, the Co layer thickness t4 is most preferably about 45Å (Sample No. 1), and if the layer thickness exceeds 150Å, a good magnetoresistive effect cannot be obtained. That is, the layer thickness t4 of the ferromagnetic layer 13 is 15
It is preferable that Å ≦ t4 ≦ 150Å (sample numbers 1 and 12 to 15). In addition, compared to FeMn, Ni
Since Mn has a large exchange bias magnetic field, when the NiMn layer is used as the antiferromagnetic layer, a large magnetoresistance change rate can be obtained by increasing the Co layer thickness t4.

Table 4 shows the layer thickness t5 of the nonmagnetic layer 14 (Cu layer).
When changing. The Cu layer thickness t5 is the first and second
Since it is the distance between the ferromagnetic layers 13 and 15, the magnetic coupling between the magnetic layers is effective. If the Cu layer thickness t5 is too thin, the second ferromagnetic layer 15 (NiFe layer) cannot be magnetized independently of the first ferromagnetic layer 13 (Co layer), resulting in a good magnetoresistive effect. Is not obtained (Sample No. 17). On the other hand, if the Cu layer thickness t5 is too thick, the probability of conduction electrons being scattered at the interface decreases, and the magnetoresistance change rate decreases (Sample No. 20). Therefore, the layer thickness t5 of the non-magnetic layer 14 is 15Å ≦ t5 ≦ 50Å
Is preferred (sample numbers 1, 18 and 19), 25Å
It can be said that the degree is optimum (sample number 1).

Table 5 shows the case where the heat treatment conditions of the antiferromagnetic layer 12 (NiMn layer) were changed. From the table, it can be seen that a larger exchange bias magnetic field is obtained as the heat treatment temperature is increased. However, the MR of the MR head is actually
Considering the use as an element, the temperature cannot be too high in the process, so the heat treatment temperature is preferably 400 ° C. (Sample Nos. 1, 22 and 2).
3).

FIG. 9 shows the temperature dependence of the exchange bias magnetic field. The sample used is Ta (50Å) / N as an example.
iMn (250Å) / Co (45Å) / Cu (25Å)
/ NiFe (100Å) / Ta (50Å) and Ta (50Å) / NiFe (70Å) / FeMn as a comparative example
(120Å) / Co (30Å) / Cu (25Å) / Ni
Fe (100 Å) / Ta (50 Å). As shown by the broken line in FIG. 9, when FeMn is used as the antiferromagnetic layer, the exchange bias magnetic field decreases monotonically with temperature, and
It becomes about 0 Oe at 50 ° C. On the other hand, when NiMn is used as in the present embodiment shown by the solid line, it is 200
It can be seen that the exchange bias magnetic field hardly changes even at ℃, and the temperature dependence is very good.

As a corrosion resistance test, the sample was left under high temperature and high humidity, and the magnetoresistance change rate was measured before and after that. The conditions were 85 ° C., 85%, and 1 week. In the spin valve film using FeMn, the characteristic deterioration was remarkable and the magnetoresistance change rate at 2.5% was 0.5% or less, but in the spin valve film using NiMn, the magnetoresistance change rate was maintained.

In addition to the above-described sample for evaluation simply formed on a 3-inch glass substrate, a sample in which a shape close to the MR element of the MR reproducing head was actually patterned by photolithography was also prepared. . The pattern shape is not particularly limited to this, but in this embodiment, it is 3 × 3 μm ^2, and a hard magnetic film and an electrode film are formed on this side surface.

FIG. 10 shows a magnetoresistance change curve of a sample patterned into a shape close to that of the MR element.
Here, the vertical axis represents the output voltage value. The film composition of the sample used is Ta (50Å) / NiMn (250Å) /
Co (45Å) / Cu (25Å) / NiFe (100
Å) / Ta (50Å). The measurement conditions are a sense current of 10 mA, an external magnetic field of ± 40 Oe and 60 Hz.
It is. As is clear from the figure, a substantially linear magnetoresistance change curve is obtained in the range of ± 40 Oe. Also,
Barkhausen noise was not confirmed in this magnetic resistance change curve, but this is because the noise was suppressed by the hard film bias method known in the field of magnetic heads.

Example 2 As a sample for evaluation, the double spin valve structure shown in FIG. 4 was formed on a 3-inch glass substrate. That is, a NiMn film is used as the first antiferromagnetic layer 42, and a second antiferromagnetic layer 4 is used.
8 is a double spin valve structure using a FeMn film. The film formation was performed using RF magnetron sputtering and ion beam sputtering as in the case of Example 1. The film forming conditions are the same as those in the first embodiment. The manufacturing process is
It is similar to that shown in FIG.

Table 6 shows the magnetoresistance change rate (%) when the layer thickness t4 of the first ferromagnetic layer 43 (Co layer) of the spin valve film produced in this Example 2 was changed.

[0072]

[Table 6]

In the spin valve structure of Table 6, the material of the underlayer 41 is Ta and NiFe (layer thicknesses t1 and t).
2), the material of the first antiferromagnetic layer 42 is NiMn (layer thickness t
3), the material of the first ferromagnetic layer 43 is Co (layer thickness t4),
The material of the first nonmagnetic layer 44 is Cu (layer thickness t5), the material of the second ferromagnetic layer 45 is NiFe (layer thickness t6), and the material of the second nonmagnetic layer 46 is Cu (layer thickness t7). , The material of the third ferromagnetic layer 47 is Co (layer thickness t8), and the second antiferromagnetic layer 48 is
Is FeMn (layer thickness t9), and the protective layer 49 is T
a (layer thickness t10).

As in the case of Example 1, since the NiMn film is used as the first antiferromagnetic layer 42, the exchange bias magnetic field is large, and the layer thickness of the Co layer, which is the first ferromagnetic layer 43, is increased. As a result, Fe is used as the first antiferromagnetic layer 42.
It can be seen that a larger magnetoresistance change rate is obtained than in the case of using the Mn film (sample numbers 25 to 27).

In Example 2 as well, a pattern of 3 × 3 μm ² was formed and the magnetoresistance change characteristics were measured. In this embodiment, since NiMn having a large exchange bias magnetic field is used as the first antiferromagnetic layer 42, the magnetization direction of the first ferromagnetic layer 43 is the same as that of the first nonmagnetic layer 44 (Cu layer). Even if it receives a magnetic field created by a flowing current, it is not disturbed so much, and the reduction rate of the magnetoresistance is small. For example, NiMn and FeMn having the same magnetoresistance change rate on a 3-inch substrate
When comparing the output voltage per unit resistance value in the two samples using the above-mentioned pattern, the sample using NiMn was 1.2 times the sample using FeMn. Thus, as the first antiferromagnetic layer 42, Ni is used.
The use of Mn is very preferable also from the viewpoint of stabilizing the magnetization direction.

The embodiments and examples described above are merely illustrative of the present invention and are not intended to be limiting, and the present invention can be implemented in various other modified modes and modified modes. . Therefore, the scope of the present invention is defined only by the claims and their equivalents.

[0077]

As described in detail above, the MR of the present invention is used.
In the element, at least an antiferromagnetic layer made of a NiMn alloy, a first ferromagnetic layer, a nonmagnetic layer and a second ferromagnetic layer are laminated in this order from the substrate side on the substrate. As described above, since the antiferromagnetic layer made of the NiMn alloy is provided closer to the substrate than the nonmagnetic layer and the second ferromagnetic layer, this NiMn alloy layer is laminated with the nonmagnetic layer and the second ferromagnetic layer. It can be previously formed and heat treated in a magnetic field. For this reason,
Even if heat treatment is performed in a magnetic field at high temperature for a long time in order to obtain good antiferromagnetism with the NiMn alloy, mutual diffusion occurs at the interface between the nonmagnetic layer and the second ferromagnetic layer, and the magnetoresistance change rate decreases. There is no inconvenience. Therefore, it is possible to provide an MR element that stably exhibits a high magnetoresistive effect.

Further, by using NiMn as the antiferromagnetic layer, a magnetoresistive element having good corrosion resistance, a sufficiently large exchange bias magnetic field, and a sufficiently high blocking temperature can be obtained. Obtainable. Further, the layer thickness of Co, which is the first ferromagnetic layer, can be increased, whereby a magnetoresistance change rate of 3% or more can be obtained.

Furthermore, the MR element of the present invention comprises, on the substrate, at least a first antiferromagnetic layer made of a NiMn alloy film,
The first ferromagnetic layer, the first nonmagnetic layer, the second ferromagnetic layer, the second nonmagnetic layer, the third ferromagnetic layer, and the second antiferromagnetic layer are arranged in this order from the substrate side. It is stacked. in this way,
In the double spin valve structure, by using the first antiferromagnetic layer that has obtained good antiferromagnetism by the NiMn alloy, it is possible to prevent the direction of the pinned magnetization from being disturbed by the magnetic field generated by the sense current. You can also

Of course, by adopting the double spin valve structure, a larger magnetoresistance change rate than that of the spin valve film having the basic structure can be stably obtained, and the resistance value between the electrodes can be lowered.

Further, according to the method for manufacturing an MR element of the present invention, the NiMn alloy layer is formed before the nonmagnetic layer or the first nonmagnetic layer and the second ferromagnetic layer are laminated and heat-treated in a magnetic field. Therefore, even if a heat treatment is performed in a magnetic field at high temperature for a long time in order to obtain good antiferromagnetism with the NiMn alloy, the non-magnetic layer or the interface between the first non-magnetic layer and the second ferromagnetic layer does not interact with each other. There is no inconvenience that diffusion occurs and the rate of change in magnetoresistance decreases. Therefore, it is possible to provide an MR element that stably exhibits a high magnetoresistive effect.

[Brief description of drawings]

FIG. 1 is a perspective sectional view showing an embodiment of an MR element according to the present invention.

FIG. 2 is a flow chart showing an example of a manufacturing process in the embodiment of FIG.

3 is a flowchart showing another example of the manufacturing process in the embodiment of FIG.

FIG. 4 is a perspective sectional view showing another embodiment of the MR element according to the present invention.

5 is a flow chart showing an example of a manufacturing process in the embodiment of FIG.

6 is a flowchart showing another example of the manufacturing process in the embodiment of FIG.

7 is a diagram showing an X-ray diffraction pattern of a NiMn film in one example having the spin valve structure shown in FIG.

FIG. 8 is a diagram showing magnetoresistance change characteristics in an example having the spin valve structure shown in FIG. 1.

9 is a diagram showing temperature dependence characteristics of an exchange bias magnetic field in an example having the spin valve structure shown in FIG. 1. FIG.

FIG. 10 is a diagram showing magnetoresistance change characteristics in an example having the spin valve structure shown in FIG. 1 and an actual MR element shape.

[Explanation of symbols]

 11, 41 Underlayer 12 Antiferromagnetic layer 13, 43 First ferromagnetic layer 14 Nonmagnetic layer 15, 45 Second ferromagnetic layer 16, 49 Protective layer 42 First antiferromagnetic layer 44 First nonmagnetic layer Magnetic layer 46 Second non-magnetic layer 47 Third ferromagnetic layer 48 Second antiferromagnetic layer

Claims (17)

[Claims] 1. An antiferromagnetic layer comprising a NiMn alloy, a first ferromagnetic layer, a nonmagnetic layer, and a second layer on a substrate.
A ferromagnetic layer is laminated in this order from the side of the substrate, and a magnetoresistive effect element having a spin valve structure. 2. The magnetoresistive effect element according to claim 1, wherein the magnetoresistance change rate is 3% or more and the exchange bias magnetic field is 100 Oe or more. 3. The thickness of the antiferromagnetic layer is 50Å to 500.
The magnetoresistive effect element according to claim 1, wherein the magnetoresistive effect element is Å. 4. Each of the first and second ferromagnetic layers comprises:
It consists of an alloy containing any one of Ni, Fe, and Co, and the layer thickness of this 1st ferromagnetic layer is 15Å-150Å, Any one of Claim 1 to 3 characterized by the above-mentioned. Magnetoresistive element. 5. The non-magnetic layer is made of any one of Cu, Ag and Au and has a layer thickness of 15Å to 50Å. Magnetoresistive effect element. 6. A first antiferromagnetic layer, a first ferromagnetic layer, a first non-magnetic layer, a second ferromagnetic layer and a second non-magnetic layer which are at least formed of a NiMn alloy film on a substrate. A magnetoresistive element having a spin valve structure, wherein a layer, a third ferromagnetic layer, and a second antiferromagnetic layer are stacked in this order from the substrate side. 7. The magnetoresistive effect element according to claim 6, wherein the magnetoresistance change rate is 3% or more and the exchange bias magnetic field is 100 Oe or more. 8. The layer thickness of the first antiferromagnetic layer is 50Å to
The magnetoresistive effect element according to claim 6 or 7, wherein the magnetoresistive effect element has a size of 500Å. 9. The first, second, and third ferromagnetic layers are each made of an alloy containing any one of Ni, Fe, and Co, and the layer thickness of the first ferromagnetic layer is 15Å. The magnetoresistive effect element according to any one of claims 6 to 8, wherein the magnetoresistive effect element has a thickness of about 150Å. 10. The first and second nonmagnetic layers are each made of any one of Cu, Ag and Au, and the layer thickness of the first nonmagnetic layer is 15Å to 50Å. The magnetoresistive effect element according to any one of claims 6 to 9, which is characterized. 11. Ta, Hf, C is formed on the bottom layer of the substrate.
The magnetoresistive effect element according to any one of claims 1 to 10, which has an underlayer made of any one metal of r, Nb, Zr, and Ti. 12. An antiferromagnetic layer comprising at least a NiMn alloy, the method comprising: a film forming step of laminating thin films on a substrate; and a heat treating step of heat treating the laminated substrates in a magnetic field. A step of sequentially stacking the first ferromagnetic layer, the non-magnetic layer and the second ferromagnetic layer, wherein the heat treatment step is performed before the non-magnetic layer and the second ferromagnetic layer are stacked. A method for manufacturing a magnetoresistive effect element having a characteristic spin valve structure. 13. The manufacturing method according to claim 12, wherein the heat treatment step is a step of forming the θ phase of the NiMn and is performed after the step of laminating the first ferromagnetic layer. 14. The manufacturing method according to claim 12, wherein the heat treatment step is a step of forming a θ phase of the NiMn, and is performed before the step of laminating the first ferromagnetic layer. 15. A first film-forming step of laminating thin films on a substrate, and a heat-treating step of heat-treating the laminated substrates in a magnetic field, wherein the film-forming step comprises at least a NiMn alloy.
Antiferromagnetic layer, first ferromagnetic layer, first nonmagnetic layer, second
Second ferromagnetic layer, second non-magnetic layer, third ferromagnetic layer and second
Magnetic layer having a spin valve structure, characterized in that the heat treatment step is performed before the first nonmagnetic layer and the second ferromagnetic layer are laminated. Method for manufacturing effect element. 16. The manufacturing method according to claim 15, wherein the heat treatment step is a step of forming a θ phase of the NiMn, and is performed after the step of laminating the first ferromagnetic layer. 17. The manufacturing method according to claim 15, wherein the heat treatment step is a step of forming the θ phase of the NiMn, and is performed before the step of laminating the first ferromagnetic layer.