JPH06325965A - Manufacture of multilayer magnetoresistance effect film - Google Patents

Abstract

PURPOSE:To provide a method for preparing multilayer magnetoresistance effect films with a large rate of magnetic reluctance change and a low hysteresis. CONSTITUTION:NiFe alloy and Cu of a specified thickness, respectively, are alternately deposited in a magnetic field by sputtering. The resultant film is annealed in a rotating magnetic field within a temperature range from 100 to 300 deg.C to obtain a magnetoresistance effect film. Or, NiFeCo alloy and Cu of a specified thickness, respectively, are alternately deposited in a magnetic field by sputtering. The resultant film is annealed in a rotating magnetic field within a temperature range from 100 deg.C to 300 deg.C to obtain a magnetoresistance effect film. Thus obtained multilayer magnetoresisance effect films have a large rate of magnetic reluctance change and a low hysteresis, and can improve the output characteristic of, for example, a magnetic head, more than conventional.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetoresistive effect film used in a thin film magnetic head, a magnetic encoder or the like which utilizes the magnetoresistive effect of a material.

[0002]

2. Description of the Related Art Heretofore, as a material for a magnetoresistive effect element (MR element), a NiFe alloy having a relatively large magnetoresistance change rate of 2 to 3% and a small hysteresis of the resistance change rate with respect to a magnetic field has been used. NiFeCo based alloys have been used alone.

In recent years, it has been desired to develop a material having a larger magnetoresistance change rate that responds to an external minute magnetic field.
Various studies have been done. For example, Fe with a thickness of 30Å
Has been developed by alternating molecular beam epitaxy of 90 and 90ÅCr (Phys. Rev. Lett. 61 (21) (19)
88), 2472: MN Baibich). However, while this material has a very large magnetoresistance change rate at low temperature of 40%, it has a problem that it is difficult to put it into practical use because it has a large saturation magnetic field of 20 kOe. , CoFe /
Attempts have been made to develop materials for multilayer films such as Cu.

As a means for manufacturing an element having a large magnetoresistance change rate, a method is known in which magnetic material layers and nonmagnetic material layers are alternately laminated. For example, if a layer of nonmagnetic material is sandwiched between a layer of magnetic material and a layer of magnetic material having a different coercive force from each other, a difference in coercive force of the magnetic material causes a gap between the magnetic layers. A method that utilizes the effect that apparent antiferromagnetic coupling occurs to increase the magnetoresistance change rate of the element, and a method of stacking a nonmagnetic material layer between layers of the same magnetic material Within the thickness range, there is a method of utilizing the effect that antiferromagnetic coupling occurs between the magnetic layers to increase the magnetoresistance change rate of the element.

Since the element of (1) has a peak of the magnetoresistance change rate when the magnetic field is near the coercive force of the smaller one of the two magnetic materials, it has a large hysteresis and is difficult to use. The element of NiFe-based alloy as the magnetic layer,
In the case of a multilayer film using Cu as the non-magnetic layer,
The rate of change in magnetic resistance is 10% or more and the saturation magnetic field can be set to about 100 Oe. However, this element also has a drawback that the hysteresis is large due to anisotropic dispersion in the magnetic material.

Further, since the magnetoresistive effect element is generally used with a bias applied, the shape of the magnetoresistive change rate curve at the position where the magnetoresistive change rate becomes half of its maximum value affects the output characteristics. . Therefore, development of a magnetoresistive effect element having a small hysteresis at this position is desired.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer magnetoresistive film in which NiFe alloy thin films and Cu thin films having a small hysteresis are alternately laminated and a multilayer magnetic in which NiFeCo alloy thin films and Cu thin films are alternately laminated. It is to provide a method of manufacturing a resistance effect film. Hereinafter, the former may be described as “NiFe alloy / Cu multilayer film” and the latter as “NiFeCo alloy / Cu multilayer film”.

[0008]

In a magnetoresistive (MR) film, when a magnetic field from the outside is applied, the magnetic domain is reversed from the outer layer where the magnetic coupling is weak. Therefore, when the magnetic domain has anisotropic dispersion. Causes hysteresis. In a multi-layer MR film, a large magnetoresistance change rate can be obtained by coupling magnetic layers antiferromagnetically, but since the hysteresis of each layer is added, the film has a large hysteresis. Become.

The inventors of the present invention performed the film formation step in a magnetic field to impart uniaxial anisotropy to the multilayer film, and then annealed it in a rotating magnetic field to reduce the anisotropic dispersion. It was found that the hysteresis can be reduced. That is,
The gist of the present invention resides in the following methods (1) and (2) of manufacturing a multilayer MR film.

(1) NiFe-based alloy and Cu are alternately deposited in a magnetic field by a sputtering method so that each of them has a predetermined thickness, and then a temperature range of 100 ° C to 300 ° C in a rotating magnetic field. A method of manufacturing a magnetoresistive effect film which is annealed.

(2) After alternately depositing NiFeCo alloy and Cu so as to have a predetermined thickness in a magnetic field using a sputtering method, in a rotating magnetic field, a temperature range of 100 ° C. to 300 ° C. A method of manufacturing a magnetoresistive effect film which is annealed.

In the present invention, the NiFe-based alloy means a binary alloy of Ni and Fe such as Permalloy (registered trademark), and the NiFeCo-based alloy is represented by Ni ₈₀ Co ₁₅ Fe. Means a ternary alloy of Ni, Fe and Co.

[0013]

The multilayer film in the method of the present invention is formed by using a sputtering method represented by an ion beam sputtering method, an RF sputtering method and the like. The sputtering method allows uniform film formation. This film forming process is performed in a magnetic field in order to impart uniaxial anisotropy to the magnetic material of the multilayer film, as described above. When the magnetic substance of the multilayer film has uniaxial anisotropy, the anisotropy in the film thickness direction becomes small. Therefore, the hysteresis can be reduced by reducing the anisotropic dispersion in the in-plane direction by the subsequent annealing.

The magnitude of the magnetic field may be larger than the magnetic anisotropy in the hard axis direction after film formation. NiFe alloys and NiFeCo
Since it is less than 10 (Oe) for the system alloys, the magnitude of the applied magnetic field should be 10 (Oe) or more, and even considering the increase in anisotropy due to thin film thickness, it is about 50 (Oe). There is enough. To apply a magnetic field, a method of sandwiching the sample from both sides with a permanent magnet can be adopted.

In the following, if necessary, NiFe alloy is used as Ni.
₈₀ Fe ₂₀ (subscripts represent atomic%; the same applies hereinafter) will be described by taking Ni ₈₀ Co ₁₅ Fe ₅ as an example of the NiFeCo alloy.

The magnetoresistive effect in the multilayer film means the sum of the magnetoresistive effect due to the anisotropy and the magnetoresistive effect caused by the multilayer structure, which is influenced by the material and film thickness of each layer.

In the case of the Ni ₈₀ Fe ₂₀ / Cu multilayer film, the first peak of the magnetoresistance change rate is present when the thickness of each layer is 15Å and 10Å, and the second peak is exhibited when the thickness is 15Å and 20Å. Similarly,
In the case of the Ni ₈₀ Co ₁₅ Fe ₅ / Cu multilayer film, the first peak of the magnetoresistance change rate is at 15Å and 19Å, and the second peak is at 15Å and 22Å.

The multilayer film in which the film thicknesses of the first peak are combined has a large magnetoresistance change rate, which is preferable in this respect.
The magnetic field at which the magnetoresistive effect is saturated also becomes large, making it difficult to put into practical use.

Therefore, it is preferable to form the film so as to form a multi-layer film in which the film thicknesses of the second peaks are combined. The multilayer film in which the film thickness of the second peak is combined has a smaller magnetoresistance change rate than the multilayer film in which the film thickness of the first peak is combined, but the magnetic field that saturates is small and is easy to put into practical use.

Since the anisotropic dispersion in the in-plane direction remains in the multilayer film thus manufactured, the hysteresis becomes large, which hinders its practical application. Therefore, in order to reduce the anisotropy in the in-plane direction, annealing is performed in a rotating magnetic field. The rotating magnetic field is applied by a method of rotating the magnetic field in a plane parallel to the film surface of the sample or rotating the sample in a static magnetic field.

The annealing is carried out at a temperature below the recrystallization temperature and below 300 ° C. so that the elements do not diffuse. On the other hand, 100 ℃
Annealing at less than 10% does not remove the dislocations and the like in the magnetic material, so there is no point in annealing. The annealing time is not particularly limited,
It takes about 30 minutes to anneal at 100 ° C, and the effect of annealing is saturated in about 60 minutes. If the annealing is performed for an excessively long time, diffusion of elements occurs and the characteristics are deteriorated. When annealing at 300 ° C, about 10 to 30 minutes is appropriate.

The rotating magnetic field applied during this annealing can rotate the magnetization vector if the strength exceeds the anisotropic magnetic field of the multilayer film, that is, the saturation magnetic field, so 100 (Oe) is sufficient.

Hereinafter, the method of the present invention will be specifically described based on Examples.

[0024]

Example 1 In a magnetic field of 100 (Oe), a Ni ₈₀ Fe ₂₀ layer (thickness 15 Å) and a Cu layer (thickness 20 Å) were alternately formed on a glass substrate by using an ion beam sputtering device to form 15 layers each. They were stacked one by one. Ni ₈₀ Fe ₂₀ and Cu were used as the target, and the film formation conditions were a back pressure of 5 × 10 ^-7 Torr and an Ar pressure of 1 × 10 ^-4 Torr.
The beam voltage was 1000 V and the current was 100 mA. The deposition rate was 2Å / sec for both metals. For comparison, a multi-layer film was prepared under the same conditions except that it was performed in the absence of a magnetic field.

The two types of multilayer films produced in this way are
In a rotating magnetic field of 100 (Oe), 80 ℃, 100 ℃, 200 respectively
Annealed at ℃, 250 ℃, 300 ℃ and 350 ℃ for 30 minutes. The MR curves of these multilayer films were drawn by the 4-terminal method and the magnitude of hysteresis was measured.

The magnitude of the hysteresis is shown in Table 1 by measuring the deviation of the curve at the peak position and the deviation of the curve at half the height of the peak.

FIG. 1 shows, as an example, the MR curve of sample No. 3 (example of the present invention) in Table 1. The hysteresis at the peak position is the amount of deviation shown as (a) in the figure, and the hysteresis at the position of half the height of the peak is the amount of deviation shown as (b).

In the case of the alloy used in this example, the magnitude of the magnetic field at which the height is half the peak of the MR curve is ± 40.
It was (Oe). The criteria for evaluation in Table 1 are ○ when the hysteresis at the peak position is 2 (Oe) or less, and when the hysteresis at the half height of the peak is 1 (Oe) or less, and when it exceeds that, × And

As can be seen from Table 1, film formation in a magnetic field
In addition, the hysteresis of the multilayer film produced by setting the annealing temperature in the rotating magnetic field at 100 ℃ to 300 ℃ is remarkably smaller than the others. The hysteresis of the magnetoresistive effect element obtained by the conventional manufacturing method is about the same as that of sample No. 8.

[0030]

Example 2 A layer of Ni ₈₀ Co ₁₄ Fe ₆ (thickness: 15) was formed on a glass substrate using an RF sputtering device in a magnetic field of 50 (Oe).
Å) and Cu layers (thickness 22 Å) were alternately laminated in 30 layers. Ni ₈₀ Co ₁₄ Fe ₆ and Cu were used as the target, and the film formation conditions were a back pressure of 5 × 10 ⁻⁷ Torr, an Ar pressure of 1 × 10 ⁻⁴ Torr, and an output of 500 W. The deposition rate was 1.5 Å / sec for Ni ₈₀ Co ₁₄ Fe ₆ film formation and 1.8 Å / sec for Cu film formation. For comparison, a multi-layer film was prepared under the same conditions except that it was performed in a non-magnetic field.

The two types of multilayer films thus produced are
In a rotating magnetic field of 100 (Oe), 80 ℃, 100 ℃, 200 respectively
Annealed at ℃, 250 ℃, 300 ℃ and 330 ℃ for 30 minutes. The MR curves of these multilayer films were drawn by the 4-terminal method, and the magnitude of hysteresis was measured in the same manner as in Example 1, and Table 2
It was shown to. Also in this case, evaluation was performed in the same manner as in Example 1.

In the case of the alloy used in this example, the magnitude of the magnetic field which is half the height of the peak in the MR curve is ± 60.
It was (Oe). As can be seen from Table 2, the film is formed in a magnetic field and the annealing temperature in a rotating magnetic field is 100 ° C to 300 ° C.
The multilayer film manufactured as above has less hysteresis than the others. Also in this case, the hysteresis of the magnetoresistive effect element obtained by the conventional manufacturing method is about the same as that of sample No. 8.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

The multilayer magnetoresistive film produced by the method of the present invention has a large magnetoresistance change rate and a small hysteresis. Therefore, when the multilayer film manufactured in this manner is used in an element, for example, a magnetic head, to which a bias is applied, the magnetoresistance change rate of the MR curve in the magnetic field is half the maximum change rate (peak). Since the hysteresis can be reduced, the output characteristic can be improved.

[Brief description of drawings]

FIG. 1 is an MR of one magnetoresistive film produced in an example.
It is a figure which illustrates a curve.

Claims (2)

[Claims] 1. NiFe-based alloy and Cu are alternately deposited in a magnetic field so as to have a predetermined thickness by a sputtering method, and then in a rotating magnetic field in a temperature range of 100 ° C. to 300 ° C. A method for manufacturing a multilayer magnetoresistive effect film, characterized by performing annealing. 2. NiFeCo alloy and Cu are alternately deposited in a magnetic field so as to have a predetermined thickness by a sputtering method, and then in a rotating magnetic field in a temperature range of 100 ° C. to 300 ° C. A method for manufacturing a multilayer magnetoresistive effect film, characterized by performing annealing.