JP2827275B2 - Magnetic resistance alloy - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive alloy exhibiting a magnetoresistive effect, and more particularly to a quaternary magnetoresistive alloy comprising Fe, Co, Ni, and Cu. It is.

[Summary of the Invention]

The present invention provides a quaternary magnetoresistive alloy mainly composed of Fe, Co, Ni, and Cu, by adjusting the composition so that the average number of electrons is 27.6 to 27.8, so that the soft magnetic properties and the magnetoresistive effect can be improved. It is intended to make a significant improvement.

[Conventional technology]

A thin film magnetic material for a so-called magnetoresistive effect type magnetic head (hereinafter, referred to as an MR head) utilizing the magnetoresistive effect is required to have soft magnetic characteristics and a large magnetoresistive effect.

 Here, the magnitude of the magnetoresistance effect is Δρ / ρ,
The resistance value when the current and the magnetization direction are parallel is ρ , Current and
The resistance value when the magnetization direction is orthogonal to ρ_⊥, In the demagnetized state
When the resistance value is ρ, it is defined by the following equation.
You.

Until now, Fe-
Ni-based alloy (so-called permalloy) thin films are known.

However, although the Fe-Ni-based alloy thin film shows good soft magnetic properties, the magnitude of the magnetoresistance effect Δρ / ρ is only about 2%, and high-density recording in the field of magnetic recording has been realized. Considering the narrow track, it cannot be said that the sensitivity is always sufficient. Therefore, development of a material having a large magnetoresistance effect is desired.

On the other hand, focusing only on the magnitude of the magnetoresistance effect, Co-
It is known that a Ni-based alloy exhibits a value of about Δρ / ρ = 6% in the composition of characteristics.

However, sufficient soft magnetic properties cannot be obtained with this Co-Ni-based alloy, and application to an MR head is difficult.

[Problems to be solved by the invention]

As described above, it is difficult to achieve both the soft magnetic characteristics and the magnetoresistance effect with the conventionally known alloy materials.

Accordingly, the present invention has been proposed in view of such conventional circumstances, and has as its object to provide a magnetoresistive alloy having excellent soft magnetic properties and a large magnetoresistance effect.

[Means for Solving the Problems] The present inventors can increase the magnetoresistance effect by adding Co to an Fe-Ni-based alloy, and supplement the soft magnetic properties deteriorated by the addition of Co with the addition of Cu. Based on the view that the alloy can be used, the study was repeated on a quaternary alloy composed of Fe, Ni, Co, and Cu. Although it was very difficult to select the optimum composition of this quaternary alloy, as a result of intensive research, it was possible to identify a composition range that exhibited excellent properties by focusing on the average number of electrons in the alloy. I came to a conclusion.

That is, the magnetoresistive alloy of the present invention is made of Fe, Co, Ni, Cu, and is characterized in that its composition is selected in the range of an average number of electrons of 27.6 to 27.8, and exhibits a magnetoresistance effect. Is what you do.

Here, the average number of electrons is a value obtained by averaging the number of electrons of each atom constituting the alloy by weighting the composition. That is, when the composition of the magnetoresistive alloy is Fe _w Co _x Ni _y C _z (where w, x, y, and z represent the ratio of each atom in atomic%), the average number of electrons is , It is obtained from the following equation (1).

According to experiments performed by the present inventors, this average number of electrons was set to 27.6
If the composition of each atom is set so as to be 27.8, the anisotropic magnetic field is small (that is, excellent in soft magnetic properties), and the magnitude Δρ / ρ of the magnetoresistance effect is a large value of 3 to 4%. There was found.

The above-described magnetoresistive alloy is usually formed by a vapor phase plating technique such as sputtering, and is often used as a magnetic material for an MR head in a thin film state. In this case, an alloy in which the composition of each atom is adjusted in advance to a value determined from the average number of electrons may be used as the evaporation source (target), or the target of each atom may be prepared individually and its area and The composition may be controlled by adjusting the applied output and the like. Furthermore, the average number of electrons is 27.6 in advance.
The composition may be controlled by combining the targets of the binary alloy set to be 27.8 and adjusting the area, applied output, and the like. For example, Fe _0.15
By combining an alloy target of Ni _0.85, an alloy target of Co _0.3 Ni _{0.7, and} an alloy target of Co _0.65 Cu _0.35 (the average number of electrons in each alloy is 27.7), a quaternary alloy with an overall average electron number of 27.7 is always obtained. A membrane can be obtained.

[Action]

The addition of Co to the Fe-Ni alloy increases the magnetoresistance effect, and the addition of Cu improves the soft magnetic properties deteriorated by the addition of Co.

In particular, the composition of these quaternary alloys has an average electron number of 27.6.
If it is set to be about 27.8, the same soft magnetic property as that of the Fe—Ni alloy is secured, and the magnitude of the magnetoresistance effect Δρ /
ρ also has a large value of 3 to 4%.

〔Example〕

Hereinafter, the present invention will be described based on specific experimental results.

Example 1 In this experimental example, a thin film magnetic material was formed in a pseudo ternary system of Ni, Cu and Fe-Co, and its soft magnetic characteristics and the optimum range of the magnetoresistance effect were examined.

The sputtering conditions at the time of film formation are as follows.

Sputtering conditions RF magnetron sputtering Ultimate vacuum 2.0 × 10 ^-6 _Torr Input power 300W Gas pressure 1.2mTorr (pure Ar) Under the above conditions, a film was formed on a glass substrate in a stripe shape with a width of 2mm and a length of 40mm. And The film thickness is 1500 ± 100
Å.

The soft magnetic properties were evaluated by measuring an anisotropic magnetic field. The anisotropic magnetic field Hk is determined by the BH loop tracer to
The H loop was measured and determined (unit: Oe). On the other hand, the magnitude of the magnetoresistance effect Δρ / ρ is such that a current flows in the length direction of the sample, and a magnetic field of 20 (Oe) and 30 (Oe) is applied to the current vertically and parallel to the sample film surface. In addition, the resistance change was measured, and Δρ / ρ (unit: Oe) was obtained.

FIG. 1 is a pseudo-ternary composition diagram showing the distribution of anisotropic magnetic field in a pseudo-ternary system of Fe _0.3 Co _0.7 and Ni, Cu, and FIG. 2 shows the distribution of the magnitude Δρ / ρ of the magnetoresistance effect. It is a pseudo ternary composition diagram shown.

FIG. 3 is a pseudo-ternary composition diagram showing the distribution of anisotropic magnetic field in a pseudo-ternary system of Fe _0.5 Co _0.5 and Ni, Cu.
The figure shows a pseudo 3 showing the distribution of the magnitude of the magnetoresistance effect Δρ / ρ.
It is an original composition figure.

FIG. 5 is a quasi-ternary composition diagram showing the distribution of anisotropic magnetic field in the quaternary system of Fe _0.7 Ni _0.3 and Ni, Cu.
FIG. 6 is a pseudo-ternary composition diagram showing the distribution of the magnitude Δρ / ρ of the magnetoresistance effect.

In each drawing, the straight line a indicates that
A straight line b represents a composition having an average electron number of 27.7, and a straight line c represents a composition having an average electron number of 27.8.

Referring to these drawings, in each case, the area between the straight line a and the straight line c, that is, the average number of electrons is 27.6 to 27.8.
It can be seen that anisotropic magnetic field is small and good soft magnetic characteristics are exhibited at the composition as follows.

Example 2 In this experiment, the average number of electrons was fixed at 27.7, the optimum range was further examined, and the influence of the heat treatment was examined. The sputtering conditions for forming each sample are the same as those in Experimental Example 1.

The targets are an alloy target of Fe _0.15 Ni _0.85, an alloy target of Co _0.3 Ni _{0.7, and} an alloy target of Co _0.65 Cu _0.35 (the average number of electrons in each alloy is 27.7)
By combining these, a ternary composition diagram was drawn as a pseudo-ternary system, and its characteristics were examined. Note that the region represented by this ternary composition diagram has a composition in which the above alloy targets are combined, and therefore, the average number of electrons is 27.7 in each case. The thickness of each sample was 0.
14 to 0.16 μm.

FIG. 7 shows a state of anisotropic magnetism in a state where sputtering is performed, and FIG. 8 shows a state of the magnitude Δρ / ρ of the magnetoresistance effect at that time. Similarly, FIGS. 9 and 10 show the anisotropic magnetic field after annealing at 300.degree.
11 and 12 show the anisotropic magnetic field after annealing at 400 ° C., and Δρ / ρ, and FIGS. 13 and 14 show 500 ° C.
Respectively show the anisotropic magnetic field and Δρ / ρ after annealing.

As is clear from these drawings, the region on the left side of the drawing shows very good soft magnetic characteristics. On the other hand, the magnitude Δρ / ρ of the magnetoresistance effect shows a very large value in the lower right region in the figure.

Therefore, if the composition is selected with emphasis on either the soft magnetic characteristics or the magnetoresistive effect according to the application, it is possible to obtain unprecedented good characteristics, and in the intermediate region between these, it is comparable to Fe-Ni alloy. Soft magnetic characteristics and a magnetoresistive effect comparable to a co-Ni alloy.

The above tendency does not change even when heat treatment is applied. Especially
Annealing up to about 400 ° C. shows no deterioration in soft magnetic properties, and the magnitude of the magnetoresistance effect Δρ / ρ is in the direction of improvement.

Example 3 In this experimental example, the characteristics (anisotropic magnetic field, magnetoresistive effect) of a representative sample to which the present invention was applied were measured using Fe-Ni alloy or Co-
Shown in comparison with Ni alloy. The sputtering conditions, film thickness, and the like are the same as in Experimental Example 1. Here, the heat treatment described in the table is an annealing treatment at 300 ° C. for 1 hour.

As is clear from this table, each sample to which the present invention is applied has a smaller anisotropic magnetic field than the Fe-Ni alloy (of course,
-Much smaller than Ni alloy. ), The value of the magnetoresistance effect is comparable to that of the Co-Ni alloy.

〔The invention's effect〕

As is clear from the above description, in the present invention
Since the composition range of the quaternary alloy composed of Fe, Co, Ni, and Cu is set to a range in which the average number of electrons is 27.6 to 27.8, Fe-Ni
Soft magnetic properties comparable to or better than that of the alloy can be obtained, and at the same time, a large magnetoresistance effect of 3 to 4% can be obtained.

Therefore, when the magnetoresistive alloy of the present invention is used for an MR head, a drastic improvement in sensitivity can be expected, and it is possible to cope with high density recording and narrow track.

[Brief description of the drawings]

FIG. 1 is a pseudo-ternary composition diagram showing the distribution of anisotropic magnetic field in a pseudo-ternary system of Fe _0.3 Co _0.7 and Ni, Cu, and FIG. 2 shows the distribution of the magnitude Δρ / ρ of the magnetoresistance effect. It is a pseudo ternary composition diagram shown. FIG. 3 is a pseudo-ternary composition diagram showing a distribution of anisotropic magnetic field in a pseudo-ternary system of Fe _0.5 Co _0.5 and Ni, Cu, and FIG. 4 shows a distribution of the magnitude Δρ / ρ of the magnetoresistance effect. It is a pseudo ternary composition diagram shown. FIG. 5 is a pseudo-ternary composition diagram showing the distribution of anisotropic magnetic field in the pseudo-ternary system of Fe _0.7 Co _0.3 and Ni, Cu. FIG. 6 shows the distribution of the magnitude Δρ / ρ of the magnetoresistance effect. It is a pseudo ternary composition diagram shown. FIG. 7 is a characteristic diagram showing a state of an anisotropic magnetic field in a quasi-ternary system composed of Fe _0.15 Ni _0.85 , Co _0.3 Ni _0.7 and Co _0.65 Cu _0.35 while being sputtered, and FIG. FIG. 9 is a characteristic diagram illustrating a state of an anisotropic magnetic field after annealing at 300 ° C., and FIG. 10 is a characteristic diagram illustrating a state of an anisotropic magnetic field after annealing at 300 ° C. FIG. 11 is a characteristic diagram showing a state of Δρ / ρ, FIG. 11 is a characteristic diagram showing a state of an anisotropic magnetic field after annealing at 400 ° C., and FIG.
A characteristic diagram showing a state of Δρ / ρ after annealing at 0 ° C.
FIG. 13 is a characteristic diagram showing a state of an anisotropic magnetic field after annealing at 500 ° C., and FIG. 14 is a graph showing Δρ /
FIG. 4 is a characteristic diagram showing a state of ρ.

Continuation of the front page (72) Inventor Koichi Aso 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (56) References JP-A-64-68982 (JP, A) JP-A-49- 17325 (JP, A) JP-B-62-54865 (JP, B2) JP-B-44-1070 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 19/00-19 / 07 H01L 43/10 H01F 1/12-1/153

Claims (1)

(57) [Claims] 1. A magnetoresistive alloy comprising Fe, Co, Ni, and Cu and having a composition selected from the range of an average number of electrons of 27.6 to 27.8, and exhibiting a magnetoresistive effect.