JP3219966B2 - Method for producing particle-dispersed magnetoresistive material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a highly sensitive magnetoresistive material used for a magnetic sensor, a magnetic head and the like. In particular, it provides a magnetoresistive effect material having a high rate of change in electric resistance in a low magnetic field.

[0002]

2. Description of the Related Art A magneto-resistive element having a magneto-resistive effect is widely used as a magnetic field sensor and a magnetic head because of its high sensitivity and relatively high output. In such magnetic sensors and magnetic heads, a DC magnetic field is applied as a bias in order to increase sensitivity and approximate a linear response. Conventionally, a magnetoresistive element has a magnetoresistance change rate of about 2%, has a small anisotropic magnetic field of about 5 Oe, which is a measure of the ease of magnetization of the film, and has a wide range of permalloy alloy thin films that are easily biased. Used.

As a method for increasing the change in electric resistance, a multilayer magnetoresistive material in which magnetic thin film layers having different coercive forces are alternately laminated is known (for example, Japanese Patent Application Laid-Open No. Hei 4 (1999) -104).
-280483). In the case of this type of multilayer giant magnetoresistive material (GMR), conduction electrons are scattered depending on the magnetization direction of the magnetic layer, and the granular GMR disperses magnetic particles in a matrix, and the conduction electrons are correlated by their magnetization. Has the problem that the scattering of In addition, it is necessary to control the thickness periodicity of the laminated film with high precision, and it is difficult to manufacture the film, requiring expensive equipment. In addition, since the obtained film is a laminated film, the processing is difficult, and depending on the application, In addition, there is a problem that various shapes cannot be manufactured. Further, this kind of multilayer film GMR can be obtained by a sputtering method or the like, but its shape is restricted, and there is a problem that a thickness of only about several mm can be obtained.

As described above, conventional magnetic sensors include those using an induced current, those using a Hall effect, and those using an artificial lattice type giant magnetoresistive effect. In addition, there are problems that a complicated circuit is required for signal processing, an advanced manufacturing method is required, productivity is low, and a strong magnetic field is required. Further, there is a problem that the manufacturing apparatus is complicated and expensive, and the characteristics are easily deteriorated by handling after the manufacturing.

Therefore, the present inventors aimed at easily manufacturing a magnetoresistive element having a large magnetoresistance change rate, and added a fine ferromagnetic element to an alloy composed of a paramagnetic element or a diamagnetic element and a ferromagnetic element. A magnetoresistive element formed by depositing magnetic particles has been developed and a patent application has been filed (Japanese Patent Laid-Open No. Hei 6-268).
280).

However, in this magnetoresistive effect material, since the deposited ferromagnetic particles have a relatively isotropic shape such as a sphere or a granular shape, the magnetoresistance effect (the rate of change of the electric resistance with respect to the magnetic field). ) Has a problem that the resistance change is not sufficient, especially in a low magnetic field.

[0007]

SUMMARY OF THE INVENTION The present invention provides a method for producing a particle-dispersed magnetoresistive material having a higher sensitivity and a higher response to a magnetic field than conventional ones. Provided is a practical magnetoresistive material exhibiting a large magnetoresistance change rate in a low magnetic field.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above problems can be solved by making magnetic fine particles having shape anisotropy exist in the same direction, and have reached the present invention. Was.

That is, the present invention provides the following (1) to (4) . (1) Alloy material obtained by dissolving a magnetic element in a non-magnetic phase
And subjected to a heat treatment with a strain of 0% <ε ≦ 80%.
With magnetic anisotropy consisting of magnetic elements
Fine particles are uniformly and finely dispersed in the non-magnetic phase in the same direction.
Method for producing magnetoresistive effect material characterized by precipitation
Law.

(2) A magnetic element is dissolved in a non-magnetic phase to form a solid solution.
And an alloy material of 1 ° C./cm<ΔT≦10
Heat treatment with a temperature difference of ° C / cm
Magnetic particles with shape anisotropy in non-magnetic phase
It is characterized by being uniformly and finely dispersed and deposited in the same direction.
Manufacturing method of a magnetoresistive effect material.

(3) The alloy material has a general formula: Cu _100-X Ni
_50-Y M ¹ _Y (where M ¹ is at least one selected from Fe and Co)
X and Y are 0.1 <X in atomic percent.
<50, 1 <Y <45)
The method for producing a magnetoresistive material according to (1) or (2).

[0012](4) The alloy material has the general formula: A _100-X M
^Two _X (However, A is at least one kind selected from Ag and Au
Element, M ^Two Is at least selected from Fe, Co and Ni
Is also one element, and X is 0.1 <X <5 in atomic percent.
The above (1) or (2), which comprises the composition represented by 0)
Of manufacturing a magnetoresistive effect material.

(5) Stress of 10 to 90% of 0.2% proof stress
The magnetoresistance effect material according to (1),
Production method.

The particle-dispersed magnetoresistive material of the present invention comprises:
Magnetic particles having shape anisotropy such as plate, needle, disk, ellipsoid, and rod are uniformly and finely dispersed in the non-magnetic matrix phase in the same direction. If the magnetic particles are isotropic, for example, spherical, granular, etc. as in the prior art, the change in resistance due to the magnetoresistive effect has a small rate of change with respect to the magnetic field, but aligns the direction of the magnetic particles with anisotropy. As a result, the signal can be increased, and the rate of change with respect to the magnetic field can be increased.

In the present invention, the size of the magnetic fine particles having shape anisotropy is preferably from 1 to 1000 nm. Outside this range, a high magnetoresistance effect, one of the objects of the present invention, cannot be obtained. Magnetoresistive effect is reduced sharply exceeds 1000 nm. From the viewpoint of the magnetoresistance effect, it is more preferably from 1 to 500 nm, and particularly preferably 1 nm.
３００300 nm.

The composition of the alloy used in the present invention is represented by the following general formula (I) or (II). Cu _100-X Ni _50-Y M ¹ _Y (I) A _100-X M ² _X (II)

Wherein M ¹ is at least one element selected from Fe and Co, A is at least one element selected from Ag and Au, and M ² is at least one element selected from Fe, Co and Ni. And X and Y are 0.1 <X <50 and 1 <Y <45 in atomic percent.

Here, Cu, Ag, and Au are paramagnetic or diamagnetic elements, and Co, Fe, and Ni are ferromagnetic elements. The present invention first, by precipitating ferromagnetic particles containing a ferromagnetic element in an alloy composed of a paramagnetic element or a diamagnetic element and a ferromagnetic element, to magnetically and compositionally non-uniform alloy, A magnetoresistive material capable of causing a resistance change can be obtained. In particular, when depositing magnetic fine particles having shape anisotropy, those having the compositions of the general formulas (I) and (II) are preferable.

It is well known that nano-sized Co particles precipitate spherically in a Cu _100-X Co _X (0.1 <X <50) alloy. However, Cu-Ni-Fe alloy (cunife: e.g. _{Cu 50 Ni 25 Fe 25, Cu} -Ni-Co
In an alloy (Kuniko: for example, Cu ₅₀ Ni ₂₅ Co ₂₅ ), aging causes spinodal decomposition, and magnetic particles are periodically deposited on a certain crystal plane. Accordingly, the composition is represented by the general formula (I). Ag (0.144) which is at least 5% or more larger than the atomic radius (0.125 to 0.128 nm) of the transition metal element which is a magnetic substance.
nm) and Au (0.144 nm) as a matrix, a magnetic substance is precipitated in a plate shape. Therefore, the composition is represented by the general formula (II).

In order to prepare a magnetoresistance effect material comprising a magnetic element having a shape anisotropy in the nonmagnetic phase of the present invention from the composition represented by the above general formulas (I) and (II), first, An alloy material formed by dissolving a magnetic element in a non-magnetic phase is prepared, a specific stress or a temperature gradient is applied to the alloy material, and a heat treatment is performed to align the direction of the magnetic fine particles having anisotropy. Each of the above steps will be specifically described.

An alloy material formed by dissolving a magnetic element in a non-magnetic phase may be formed into a supersaturated solid solution or a forced solid solution, for example, at a cooling rate of 10 ² K / sec or more. Examples of the method of cooling at a cooling rate of 10 ² K / sec or more include vapor deposition methods such as vacuum deposition, ion plating, and sputtering, liquid quenching methods such as melt spin, gas atomization, and liquid spinning, and water quenching from a high temperature. .

The alloy material to be produced can be made into a thin film, a ribbon, a powder, a wire or the like depending on the application. Further, in the present invention, a powder may be prepared, and the powder may be aggregated and solidified to form a bulk (solidified material). In this case, solidification molding is first performed, and then heat treatment is performed. The final shape (product shape) may be formed after solidification or heat treatment.

The heat treatment temperature is 200 to 600 ° C. By heat treatment at 200-600 ° C for 30 minutes or more,
Fine ferromagnetic fine particles are deposited, and a large magnetoresistance effect is obtained. More preferably, the heat treatment temperature is 300 to 50.
By setting the temperature to 0 ° C., a greater magnetoresistance effect can be obtained. If the heat treatment temperature is lower than 200 ° C., ferromagnetic fine particles having a desired size cannot be obtained. On the other hand, when the temperature exceeds 600 ° C., the deposited ferromagnetic fine particles become too large, and a material having a magnetoresistance effect, which is the object of the present invention, cannot be obtained. In addition, when the temperature is high and the time is short, uniformity at the time of precipitation is easily lost.

By applying the above-mentioned heat treatment by applying a stress or a temperature gradient during the heat treatment, the magnetic fine particles having anisotropy can be oriented and deposited in a uniform direction. Specifically, when aging a supersaturated solid solution of an alloy in which these magnetic particles precipitate with an anisotropic shape, for example, from an arbitrary direction or a certain crystal plane, for example, (1) 0% <ε ≦ 80% strain, preferably 1% ≦ ε ≦
(2) Temperature difference in one direction is 1 ° C./cm≦ΔT≦10° C./c
m, desirably 2 ° C./cm≦ΔT≦5° C./cm and aging can make the precipitation directions uniform. Further
The 10% of 0.2% proof stress (3) aging temperature 90
%, Preferably under 50% to 90% stress.

As described above, by aligning the direction of the particles having nano-sized magnetic particles having anisotropy (plate shape, needle shape), the response to a magnetic field and the signal change are increased, and the desired performance as a magnetic sensor is obtained. Is shown.

As heat treatment under stress, 0.2% proof stress 1
In the case of aging under a stress of 0% to 90%, if it is less than 10%, it is difficult to align the directions of the magnetic fine particles. The stress is more preferably 50 to 90% because the direction of the magnetic fine particles can be easily aligned.

When aging under stress is indicated by another index, aging at a strain of 0% <ε ≦ 80% is given when the strain is ε, and when the strain exceeds 80%, the crystal becomes fine. As a result, the electric resistance increases and the magnetoresistance ratio decreases.

In aging by giving a temperature difference in one direction, 1 ° C.
If the temperature difference is less than / cm, it is difficult to align the directions as described above.

As described above, the present invention has anisotropy by subjecting an alloy system on which anisotropic magnetic particles are precipitated to aging by applying stress aging, strain aging, and temperature difference. The main objective is to orientate and deposit magnetic particles to make an excellent magnetoresistive sensor. By using this method, the volume of the magnetic fine particles can be increased without reducing the area of the interface between the magnetic material and the non-magnetic material that contributes to the magnetoresistance effect as schematically shown in FIG. From this, the magnetic field is not easily disturbed by heat (room temperature), and the response of the magnetization of the magnetic fine particles to an external magnetic field is improved. Therefore, the magnetoresistance effect shows a large change at a lower magnetic field. In addition, since the magnetic particles arranged periodically tend to cooperatively become ferromagnetic due to the interaction, they are ferromagnetically coupled with a low external magnetic field, and the electric resistance is reduced.

By giving a stress and temperature gradient, FIG.
As shown in (1), magnetic fine particles 2 having shape anisotropy are uniformly dispersed in a matrix 1 having non-magnetism.

[0031] Figure 2 after solution treatment the Au ₉₀ Co _10, a transmission electron microscope (TEM) image of a sample 1 hour aging treatment at 300 ° C., 3 after solution treatment the Au ₉₀ Co ₁₀ 5 % in the direction of the arrow at 300 ° C for 1 hour
5 is a TEM image of a sample given strain aging.

In the normal aging shown in FIG.
Precipitation of particles (linear in the photograph) is observed, which is uniformly precipitated in three directions in the horizontal and vertical directions and parallel to the paper surface. On the other hand, in the sample subjected to the strain aging of 5 % in FIG. 3, Co particles are precipitated only perpendicularly to the strain direction. The magnetic resistance ratio increased from 8% to 18% due to the uniform precipitation direction of the plate-like Co particles. Thus, in the present invention, by aligning the directions of the anisotropic magnetic particles, it is possible to solve the problem of the particle dispersion type magnetoresistance effect, that is, the small change in resistance at a low magnetic field.

[0033]

The present invention will be described below in more detail with reference to examples and comparative examples. Example 1 A master alloy having an atomic ratio of Ag ₈₅ Co ₁₅ was melted in an arc melting furnace or a high-frequency melting furnace to prepare a target having the above composition, and this was sputter-deposited on a water-cooled polyimide substrate. This sample was subjected to a 5% tensile strain by bending the film deposited on the substrate together with the substrate, and aged at 500 ° C. for 1 hour. The magnetic properties of the sample were measured by VSM (vibration-type magnetization measurement), and the resistance was measured by a four-terminal method with an applied magnetic field of 15 kOe. As a result, the magnetoresistive effect ratio (ΔR / R%) was 32%.

Comparative Example 1 In Example 1, no tensile strain was applied,
The usual aging of time was done. The magnetoresistance effect ratio at an applied magnetic field of 15 kOe was 20%.

Example 2 A master alloy having the composition (atomic ratio) shown in Table 1 was melted in an arc melting furnace or a high-frequency melting furnace, homogenized in a vacuum at 1000 ° C. for 2 hours, and rapidly cooled in ice water. completely or <br/> unit content to be dissolved. Thus, a bulk (cast) material was obtained. The sample of Example 2 was given a 10% compressive strain and aged at 300 ° C. for 1 hour. The magnetoresistance effect ratio of the sample of Example 2 was 18%.

Comparative Example 2 In Example 2, normal aging was carried out at 300 ° C. for 1 hour without compressive strain. Table 1 shows the results.

Example 3 A columnar bulk material (cast material) was prepared from a mother alloy having the composition shown in Table 1 in the same manner as in Example 2, and then the bulk material was subjected to thinning to obtain a thin wire. . By moving the sample in a small furnace in a soaking zone, a temperature difference of 4 ° C./20 mm was given, and aging was performed at 300 ° C. for about 1 hour. Table 1 shows the results.

Comparative Example 3 In Example 3, normal aging was performed at 300 ° C. for about 1 hour. Table 1 shows the results.

[0039]

[Table 1]

[0040]

As described above, the magnetic fine particles having shape anisotropy obtained by the present invention are uniformly and finely dispersed in the same direction, so that the magnetic particles randomly precipitate in the tissue by ordinary aging. It has a more sensitive change in resistance than that of the one, and is particularly excellent in magnetoresistance effect ratio in a low magnetic field.

[Brief description of the drawings]

FIG. 1 is a schematic view of a magnetoresistive material of the present invention.

FIG. 2 is a TEM image of a material subjected to normal aging.

FIG. 3 is a TEM image of a material in which magnetic fine particles having shape anisotropy according to the present invention are dispersed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-magnetic parent phase 2 Magnetic fine particles having shape anisotropy

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H01L 43/12 G01R 33/06 R H01F 1/30 (56) References JP-A-6-318749 (JP, A) JP-A Heisei 6-268280 (JP, A) JP-A-7-86017 (JP, A) European Patent Application Publication No. 638943 (EP, A1) Material of the Institute of Magnetics, IEICE, Vol. MAG-94, no. 85-100, pp. 1-5 (1994) Materials of the Institute of Electrical Engineering Magnetics, Vol. MAG-93, No. 126-131 pp. 1-8 (1993) (58) Fields studied (Int. Cl. ⁷ , DB name) H01L 43/08 G01R 33/09 G11B 5/39 H01F 1/20 H01L 43/10 H01L 43/12 JICST file (JOIS )

Claims (5)

(57) [Claims] An alloy material formed by dissolving a magnetic element in a non-magnetic phase is subjected to a heat treatment by applying a strain of 0% <ε ≦ 80% to form a non-magnetic phase. A method for producing a magnetoresistive material, wherein magnetic fine particles having anisotropy are uniformly and finely dispersed and precipitated in a nonmagnetic phase in a uniform direction. 2. An alloy material in which a magnetic element is dissolved in a non-magnetic phase is prepared, and the alloy material is added to the alloy material at 1 ° C./cm<ΔT≦10° C.
The magnetoresistive effect is characterized in that heat treatment is performed by giving a temperature difference of 1 cm and magnetic fine particles having shape anisotropy composed of magnetic elements are uniformly and finely dispersed and deposited in the non-magnetic phase in the same direction. Material manufacturing method. 3. The alloy material has the general formula: Cu _100-X Ni _50-Y
M ¹ _Y (where M ¹ is at least one element selected from Fe and Co, and X and Y are 0.1 <X <5 in atomic percent)
3. The method for producing a magnetoresistive material according to claim 1, wherein the composition has a composition represented by the following formula: 0, 1 <Y <45). 4. An alloy material having a general formula: A _100-X M ² _X (where A is at least one element selected from Ag and Au, and M ² is at least one element selected from Fe, Co and Ni)
3. The method for producing a magnetoresistive material according to claim 1, wherein the seed element, X, has a composition expressed by atomic percent of 0.1 <X <50). 5. The method according to claim 1 , wherein the heat treatment is performed under a stress of 10% to 90% of 0.2% proof stress.