JPS5877208A - Multi-layer magnetic thin film and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent the generation of a closed circuit magnetic domain by a method wherein the easy magnetizing axis of each magnetic layer is alternately and obliquely crossed when magnetic layers having uniaxial magnetic anisotropy are stacked through a magnetic insulating layer. CONSTITUTION:A multi-layer magnetic thin film is formed by stacking magnetic layers 602, 604 having uniaxial magnetic anisotropy through a magnetic insulating layer 603. At that time, the direction of easy magnetizing axis of each magnetic layer is established to alternately and obliquely cross. For example, the easy magnetzing axis is directed to the (a) or (b) direction alternately forming an angle of psi each other. When a magnetic field is applied to the multi-layer magnetic thin film in the (h) direction, the magnetization of each magnetic layer directs to the directions of Ma, Mb respectively. Therefore, when a core side face is established on a bisector at the angle psi, the core width direction component of the magnetization can alternately be directed to the opposite direction respectively. This can prevent the generation of a closed circuit magnetic domain.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer magnetic thin film and a method for manufacturing the same.
ii. A magnetic thin film and a method for manufacturing the same.

For example, it is reported in NATtJRF that the coercive force of a N i -p 6 alloy thin film is significantly reduced by laminating the thin non-magnetic layer through an extremely thin non-magnetic layer, that is, a magnetic insulator 1-.

194.1035 (1962), and it is therefore a well-known fact that this material is suitable as a high-frequency magnetic core material for thin-film magnetic heads and the like.

A magnetic head using such a multilayer magnetic thin film is, for example, formed by forming a first permalloy (Nlpe alloy) layer 2 on a substrate 1, as shown in FIG. 3. Magnetic insulating non-magnetic layer of the electrically insulating and multilayer magnetic thin film for forming active camps above. Second permalloy layer 4
．． Electrical insulating layer 51 Current conductor 6. Electrical insulation layer7.
Third permalloy layer8. It consists of a nonmagnetic layer 91 and a fourth permalloy layer 10. Here, the first and second permalloy layers form a first multilayer magnetic thin film magnetic core.

The third and fourth permalloy layers serve as the 7% second multilayer magnetic thin film magnetic core. In such a conventional magnetic head, the direction of the axis of easy magnetization in the layer plane of each permalloy layer is set parallel to the magnetic recording medium facing surface 11 (perpendicular to the plane of the paper in FIG. 1), and the high frequency of the magnetic core is It has been devised to ensure the characteristics.

By the way, when the axis of easy magnetization is set parallel to the surface facing the magnetic recording medium, the above-mentioned magnetic thin film will form a closed magnetic domain such that the magnetization forms a closed magnetic path on the side surface of the magnetic thin film, as schematically shown in FIG. 12 occurs, which impairs the magnetic core characteristics, which is a particular drawback of thin-film magnetic heads.

The disadvantage of this is that the core width becomes narrower.

This becomes more noticeable as the core thickness increases. especially.

As the core thickness increases, the occurrence of the closed magnetic domain becomes more noticeable because the influence of the demagnetizing field when magnetization is directed in one width direction becomes stronger as the core thickness increases.

An object of the present invention is to provide a multilayer magnetic thin film that eliminates such drawbacks.

Another object of the present invention is to provide a method for manufacturing a multilayer magnetic thin film that eliminates the above-mentioned drawbacks.

The above-mentioned drawbacks of conventional magnetic thin films arise because the direction of magnetization is not necessarily different in the FJ direction, not only in the case of single-layer films but also in the case of multi-layer films. In the multilayer magnetic thin film according to the present invention, by selecting an appropriate direction for the core side surface when forming the core, it is possible to alternately direct the core width direction components of the magnetization inside each magnetic layer in substantially opposite directions. Similarly, the direction of the axis of easy magnetization inside each magnetic layer is determined.

Namely, in the multilayer magnetic thin film according to the present invention, magnetic layers having -axis magnetic anisotropy are laminated with magnetic insulating layers interposed therebetween, and the directions of the easy axes of magnetization inside each of the magnetic layers are alternately obliquely crossed. It's set up just fine. For example, as shown in Figure 3, the easy axes of magnetization inside each magnetic layer are alternately ψ
When applying a sufficient magnetic field in the h direction to such a multilayer magnetic thin film (a magnetic field larger than the anisotropic magnetic field of the magnetic anisotropy of each magnetic layer), , h, and the angle θ between a and b, and θ1 are both smaller than 90', select the h direction, apply the above magnetic field, and then remove the applied magnetic field, the magnetization inside each magnetic layer will change. is the direction in which the applied magnetic field direction component of each approximate axis of easy magnetization is parallel to the applied magnetic field, that is, @ M s
Turn towards 9M b. Therefore, a direction and b
By setting the core side surface perpendicular to the bisector of the angle ψ formed by the direction, by applying the magnetic field as described above,
The core width direction components of the magnetization inside each magnetic layer can be directed in substantially opposite directions alternately, so that the demagnetizing field in the core width direction is also weak, and the generation of the closed magnetic domains described above can be eliminated. By the way, in a normal magnetic thin film having -axis magnetic anisotropy, the direction of the local easy axis of magnetization is within a certain range of angles around the direction of the average easy axis of magnetization, although it also depends on the fabrication properties. It is dispersed throughout. This dispersion angle can be determined, for example, by measuring the residual total magnetic moment when a sufficiently strong magnetic field H is applied to the magnetic thin film and removed by increasing the angle α formed with the average easy axis of magnetization, as shown in Figure 4. from where it dropped to 90%.

Angle change Δα until reaching 90% of the saturation value on the opposite side
It can be defined as 1/2 of (see Figure 5).

Thus, when defining the dispersion angle of the easy axis of magnetization,
If the above ψ is set to a value larger than the two dispersion angles, that is, Δα, and a sufficiently strong magnetic field is applied in the direction θ1 = θb, even if there is dispersion in the distribution of the local easy axis of magnetization, the above Thus, the magnetization of each layer can be directed in the directions of M and Mb, respectively, and the generation of closed magnetic domains can be prevented. However, if the magnetic permeability in the h direction is as high as possible,
In addition, in order to ensure magnetic field response with good linearity, ψ
It is desirable that ψ be as small as possible. Therefore, by setting ψ approximately equal to Δα, it is possible to obtain a multilayer magnetic thin film that has high magnetic permeability in the h direction and does not generate closed magnetic domains. .

The multilayer magnetic thin film according to the present invention as described above is as follows.

Vacuum deposition, commonly used to form thin films on a suitable substrate (either magnetic or non-magnetic).

May Shima CV D (chemical vapor
When a magnetic material and a magnetically insulating material are alternately deposited by a method such as deposition, a magnetic field is applied during each magnetic field formation, and the direction of the applied magnetic field is alternately changed by a predetermined angle. can. The above-mentioned applied magnetic field does not necessarily have to be a static magnetic field, but may include a magnetic field that oscillates around a specific axis, a magnetic field in which the tip of the magnetic field vector traces an elliptical trajectory, and other internal fields in the process of forming each magnetic layer. A magnetic field may be applied such that the direction in which magnetization stays the longest is alternately changed.

The effect of the present invention is also achieved when the magnetic layers have substantially equal thicknesses and have substantially equal saturation magnetic flux densities.

It is clear that this can be particularly ensured by making the number of magnetic layers even, since the free magnetic poles that appear on the side surfaces when the core is formed as described above cancel each other out. For the same reason, when the magnetic layer is composed of three layers, the thickness of the intermediate layer is made approximately equal to the sum of the thicknesses of the other two magnetic layers sandwiching the intermediate layer. It is also clear that this effect is expected.

When the multilayer magnetic thin film according to the present invention is placed under conditions such as a magnetic rad core material where the strength of an externally applied magnetic field changes with location and the internal magnetization is partially switched, the magnetization is switched. A domain wall occurs at the boundary between the switched and non-switched parts. At this time, under conditions in which the direction of the applied magnetic field does not change subtly but only the direction, if the type of domain wall that is stable in the state where no external magnetic field is applied is a Neel domain wall, the above boundary will have a 360°
There is a problem in that the zero domain wall is accumulated every cycle of the switch, and this portion deteriorates the responsiveness of magnetization to an external magnetic field. This problem can be alleviated if the type of domain wall that is stable in the absence of an external magnetic field is a cross-tied domain wall rather than a Neel domain wall, and it does not occur at all if it is a Bloch domain wall. Which type of domain wall is stable depends on the type of magnetic thin film, but when the film thickness is thin, the Neel domain wall is stable, sb, and as the film thickness increases,
It is well known that the cross-tied domain wall and then the Bloch domain wall become stable (for example, see Shokabo: Applied Physics Selection, "Thin Film", p.287-p.288).

In principle, the thickness of the magnetic insulating layer in the present invention is 2
~3 atomic layers is sufficient, but since it is difficult to actually form a film of this thickness without pores, it is usually several nm or more, preferably lQnm or more, and depending on the material. is preferably 1100n or more. In principle, any non-magnetic material may be used as the material for forming the magnetic insulating layer, but s8i0. , SiO,
Electrical insulating materials such as A-08, CO, A-e, Au
etc. metals.

Semiconductors such as Bi, in some cases organic rings, can be used depending on the purpose.

The invention will be explained below with reference to examples.

As shown in FIG. 6, approximately 80% Ni
%, about 20% Fe and SiO were alternately vacuum-treated in a magnetic field by conventional means to produce a multilayer magnetic thin film with two magnetic layers. At this time, the first permalloy layer 6
Direction a of the applied magnetic field during formation of 02 and second permalloy layer 6
The angle ψ made with the direction of the applied magnetic field when forming 04 is 10',
5olO'.

Various multilayer magnetic thin films with different thicknesses of 200, 400.60", and 900" were fabricated. The thickness of the first and second permalloy layers was about 0.5 μm. 5sio layer 603
The thickness was approximately 0.1 μm. The thus obtained multilayer magnetic thin film was etched using a conventional etching method to produce a rectangular microelement as shown in FIG. 7, and a magnetic field was applied in the y direction (perpendicular to the bisector of the angle ψ). After applying the magnetic field to saturate the magnetization, we observed the magnetic domains that appeared in the device when the magnetic field was removed.

As a result, it was confirmed that magnetic domains were hardly generated in elements in which θ was 10' or more. For reference, the dispersion angle of the easy axis of magnetization in a single-layer permalloy film with a thickness of 0.5 μm, which was simultaneously prepared, was approximately 50, and the effect of the present invention was confirmed in a multilayer magnetic thin film with θ of 100 or more. That's why.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a thin film magnetic head that is an application example of the present invention, FIG. 2 is a diagram of magnetic domain patterns generated in a fine magnetic thin film element, and FIG. 3 is an easy axis of magnetization of the multilayer magnetic thin film of the present invention. 4 and 5 are vector diagrams and line diagrams for explaining the method of measuring the dispersion angle of the easy axis distribution of magnetization inside the magnetic thin film. FIG. This is a sectional view of a multilayer magnetic thin film in an example, and FIG. 7 is a partial view seen from the top when a fine element is formed using the multilayer magnetic thin film of the above example. 1.601...Substrate, 2, 4, 8, 10, 602°6
04... Magnetic layer (602 and 604 are permalloy layers), a, 9, 603... Magnetic insulating layer (603 first
Figure Z Figure ■ Mu Figure 2 <'FJ7 Continuation of old page 1 0 Inventor Yoshihiro Shiroishi Hitachi, Ltd. Central Research Laboratory, 1-280 Higashikoigakubo, Kokubunji City

Claims (1)

[Claims] 1. In a multilayer magnetic thin film formed by laminating magnetic layers having -axis magnetic anisotropy via magnetic insulating layers, the directions of the easy magnetization axes of the magnetic layers are alternately obliquely crossed. A multi-magnetic, thin film that is characterized by its unique properties. 2. The multilayer magnetic thin film according to claim 1, characterized in that the angle formed by the obliquely intersecting easy axes of magnetization is made larger than twice the dispersion angle of the easy axes of magnetization inside each magnetic element. . 3. The multilayer magnetic thin film according to claim 1, wherein the angle formed by the obliquely intersecting easy axes of magnetization is approximately twice the dispersion angle of the easy axes of magnetization within each magnetic layer. 4. Claims 1 to 3 of claim x, characterized in that the magnetic layer is composed of an even number of magnetic layers having substantially equal saturation flux density and thickness.
A multilayer magnetic thin film with 6 self-contributions to any of the terms. 5. Consisting of three magnetic layers in which the saturation magnetic flux density of each magnetic layer is approximately equal, and the thickness of the middle of the magnetic layers,
The multilayer magnetic thin film according to any one of claims 1 to 3, characterized in that the thickness is approximately equal to the sum of the thicknesses of two other magnetic layers sandwiching the magnetic layer. 6. The thickness of each magnetic layer is set to such a thickness that a cross-tie domain wall or a Bloch domain wall is the most stable type of domain wall when no external magnetic field is applied.
The multilayer magnetic thin film according to any one of items 1 to 5. 7. The multilayer magnetic thin film according to any one of claims 1 to 6, characterized in that a magnetic metal layer containing Ni and Fe as main components is used as the magnetic layer. 8. - A method for manufacturing a multilayer magnetic thin film in which magnetic layers having axial magnetic anisotropy are laminated via a magnetic insulating layer, in which a magnetic material and a magnetic insulating material are alternately deposited on a substrate to form a multilayer magnetic thin film. A method for producing a multilayer magnetic thin film, which comprises applying a magnetic field when forming each magnetic layer, and alternately changing the direction of the applied magnetic field by a predetermined angle layer.