JPS62249408A - Ferromagnetic thin film - Google Patents

Abstract

PURPOSE:To facilitate a control of magnetic anisotropy by impressing stress upon a ferromagnetic thin film and providing the thin film with magnetic anisotropy after forming such thin film. CONSTITUTION:When uniaxial stress sigma is impressed inside a film face of ferromagnetic thin film, uniaxial magnetic anisotropy K is given in parallel with sigma. If a magnetostrictive constant of ferromagnetic thin film is lambdas, K is shown by =3lambdassigma/2. In addition, lambdas of Fe-Co-Si system alloy thin film which is vacuum deposited with a photoceram substrate is -0.5X10<-6> and its easy magnetizing direction is in parallel with a longitudinal direction and then its magnetic anisotropic constant K is shown by K=6.25X102erg/cm<3>. Subsequently, when a substrate 13 is bent by using a jig 11 and stress such as sigma=1.20X10<9>g/cm<3>is impressed upon the ferromagnetic thin film 14, the magnetic anisotropic constant is shown by K=-2.30X10<2>erg/cm<3>. Moreover, variation of magnetic anisotropy K is -9.0X10<2>erg/cm<3> and is shown by K=-2.5X10<2>erg/cm<3>. Magnetic anisotropy, therefore, is given in an optional direction by impressing stress upon the ferromagnetic thin film after forming such ferromagnetic thin film and its degree can be controlled by that of stress sigma.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ferromagnetic thin film in which the direction and magnitude of magnetic anisotropy are controlled.

[Conventional technology]

BACKGROUND OF THE INVENTION With the increasing density of magnetic recording, a magnetic head using a ferromagnetic thin film having a high saturation magnetic flux density and a high dielectric constant is strongly desired. Generally, among the above-mentioned ferromagnetic thin films, the magnetic permeability of a thin film having uniaxial magnetic anisotropy at high frequencies is small in the direction of easy magnetization and large in the direction perpendicular to the direction of easy magnetization (direction of difficult magnetization). Therefore, in a magnetic head that operates by a magnetic flux flowing in the in-plane direction of a ferromagnetic thin film attached to a substrate, it is desirable that the direction in which this magnetic flux flows is the direction in which magnetization is difficult.

Therefore, controlling the direction and magnitude of the magnetic anisotropy of a ferromagnetic thin film is extremely important in manufacturing a magnetic head.

Conventionally, as a method for controlling magnetic anisotropy, Japanese Patent Application Laid-Open No. 59
As shown in Japanese Patent Laid-Open No. 59-63706, striped unevenness is formed in a predetermined direction on the magnetic film surface, or
As shown in No. 3707, there was a method of periodically changing the composition of the magnetic film. However, all of the above conventional methods require a photoresist process, which takes a lot of time.

It was also a technically difficult method.

[Problem that the invention seeks to solve]

The present invention provides a magnetic anisotropy control technique that does not require a technically difficult and time-consuming process such as a photoresist process.

[Means for solving problems]

In the present invention, the inverse magnetostriction effect of a ferromagnetic thin film is utilized in order to impart magnetic anisotropy of any magnitude in any direction within the film plane of the ferromagnetic thin film.

When a uniaxial stress σ is applied within the film plane of a ferromagnetic thin film, a uniaxial magnetic anisotropy ΔK is imparted parallel to σ. If the magnetostriction constant of the ferromagnetic thin film is λS, then Δ is expressed by the following relation: 3λSσ Δ=−. Therefore, as shown in the above equation, the magnitude of the uniaxial magnetic anisotropy ΔK can be controlled by changing the magnitude of the uniaxial stress σ applied, and the uniaxial magnetic anisotropy ΔK can be controlled by changing the direction of the uniaxial stress σ applied. The direction of anisotropy can be controlled.

[Effect]

In other words, if a ferromagnetic thin film is deposited on a substrate with a strain applied to it by, for example, curving the substrate in advance, then when the strain on the substrate is removed after film formation, stress σ will be applied to the ferromagnetic thin film. applied. By controlling the direction and magnitude of σ.

Magnetic anisotropy of any magnitude can be imparted to a ferromagnetic thin film in any direction. Therefore, the method of the present invention is very simple and the time required for the process is short.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

[Example 1] 10 yn X 3 mm X 0, 3 m t
Fe −
A Go-Si alloy was vacuum deposited. Fa-Go-
The composition of the 8i alloy thin film is F e 5za7c in weight%.
o o, ss i te, a, and the film thickness is 1.8
0 μm, and the magnetostriction constant λS was −o, 5×10 −s.

When the sum of the shape magnetic anisotropy of the above ferromagnetic thin film and the magnetic anisotropy of the film itself was measured using a torque meter, the easy magnetization direction was parallel to the longitudinal direction of the ferromagnetic thin film, and the magnetic anisotropy The constant was 6.25×10”erg/a+?

Further, using a jig 11 as shown in FIG. 1, the substrate 13 was bent with screws 12, and stress was applied to the ferromagnetic thin film 14. In this case, the direction of the applied stress is 15 in Figure 1.
This is the direction indicated by .

In this example, σ=1.20X10g in this direction 15
When a stress of g/cJ was applied, the magnetic anisotropy constant of the ferromagnetic thin film was -2,30 The direction was the direction of easy magnetization, but because stress was applied, the longitudinal direction of the thin film became the direction of difficult magnetization.

On the other hand, the amount of change Δ in magnetic anisotropy calculated from Δ=3λSσ/2 is −9.0×10”erg/ffl,
Therefore, K is calculated to be = -2.5 x 10'' erg/ci, and this value almost agrees with the experimental results.

As mentioned above, by applying stress to the ferromagnetic thin film after forming the ferromagnetic thin film, magnetic anisotropy can be imparted to the ferromagnetic thin film in any direction, and the magnitude thereof depends on the applied stress σ can be controlled by the size of the

[Example 2] A Ta thin plate with a thickness of 50 μm with a hole of 8 rmφ was placed on a Photolasem substrate manufactured by Corning Inc. with a size of 10 nnφX 0 and 3 tm t , and in this state Fe-G
o -Si alloy is formed on the substrate by sputtering method.
I did it. The film thickness was 1.52 μm, and the composition and magnetostriction constant were the same as in Example 1. The magnetic anisotropy constant of the 8 Imφ sputtered sample thus produced was measured using a torque meter and was found to be K=53 erg/aJ.

On the other hand, a photoceram substrate covered with a Ta thin plate with an 8-φ hole was mounted on a jig 11 as shown in FIG. 1, sputtering was performed in this state, and the substrate was removed from the jig 11 after sputtering was completed. That is, in this case, a uniaxial compressive stress is applied to the ferromagnetic thin film. Table 1 and FIG. 2 show the relationship between the magnetic anisotropy constant of the ferromagnetic thin film thus produced and the radius of curvature R of the substrate during sputtering.

As shown in Table 1 and FIG. 2, there is a nearly linear relationship between the reciprocal 1/R of the substrate curvature diameter and K, and it can be seen that by changing R, any K can be obtained.

Further, in this example, since λS is negative, the direction parallel to the compressive stress application direction was the easy magnetization direction.

As mentioned above, by applying stress to the ferromagnetic thin film after forming the ferromagnetic thin film, magnetic anisotropy can be imparted to the ferromagnetic thin film in any direction, and the magnitude of the magnetic anisotropy depends on the radius of curvature of the substrate. It can be controlled by the magnitude of R.

〔Effect of the invention〕

As explained above in detail, the ferromagnetic thin film of the present invention is provided with magnetic anisotropy of an arbitrary magnitude in an arbitrary direction.

Furthermore, the production of the ferromagnetic thin film of the present invention does not require a time-consuming process such as a photoresist process, which was conventionally required to impart magnetic anisotropy. Can be made in time.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the stress application method in the ferromagnetic thin film of the present invention, and FIG. 2 is a graph showing the relationship between the reciprocal of the radius of curvature of the substrate and the magnetic anisotropy constant in Example 2 of the present invention. . 11... Jig, 12... Screw, 13... Board, 1
4...Ferromagnetic thin film, 15...Stress direction. VJ, Figure T 2 Figure'/R (cm, -ri)

Claims (1)

[Scope of Claims] 1. A ferromagnetic thin film characterized in that magnetic anisotropy is imparted to the ferromagnetic thin film by applying stress to the ferromagnetic thin film after forming the ferromagnetic thin film. 2. The ferromagnetic thin film according to claim 1, wherein the ferromagnetic thin film is formed by a sputtering method or a vapor deposition method. 3. Claim 2, characterized in that the ferromagnetic thin film is formed on a substrate that has been previously strained, and stress is applied to the ferromagnetic thin film by removing the strain on the substrate after film formation. The ferromagnetic thin film described in . 4. The ferromagnetic thin film according to claim 3, wherein the film is formed on a substrate that has been strained by curving it, and after the film formation, the strain applied to the substrate is removed. .