JPS63219114A - Heat treatment of magnetic thin film - Google Patents

Abstract

PURPOSE:To improve the high-frequency characteristics of a thin film magnetic core of a magnetic thin film pattern by simultaneously applying a fixed unidirectional magnetic field and a rotating unidirectional magnetic field to the film surface of the magnetic thin film pattern and performing a heat treatment. CONSTITUTION:When a fixed unidirectional magnetic field 3 is applied in a particular direction of the pattern of a thin film magnetic core 1 and the magnitude of the magnetic field 3 is made larger than the demagnitizing field, magnetization is provided in the magnetic field 3 direction. Further, when a rotating unidirectional magnetic field 4 is applied in superposition, a magnetic field having a peak in the magnetic field 3 direction is effectively added to the pattern independently of the change of the effective magnetic field due to the demagnitizing field. When a heat treatment is performed in such magnetic field, an easy magnetizing axis is given in the direction of magnetic filed 3, and an anisotropy is imparted which is somewhat diverging, centering on this axis. With this, the direction and magnitude of the anisotropy can be made to be desired ones, and a thin film head having excellent high-frequency characteristics is obtained using such thin film magnetic core.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of heat treatment in a magnetic field for a thin film magnetic core, and particularly aims to provide a thin film magnetic core with excellent high frequency characteristics that can be used in a thin film magnetic head to obtain good results. It is something.

Conventional technology Conventionally, in magnetic cores used at high frequencies, especially in magnetic cores formed of magnetic thin films, the axis of easy magnetization of the magnetic thin film is given in a direction approximately perpendicular to the direction in which magnetic flux flows, that is, the direction in which the magnetic core is used is difficult to magnetize. It is known that high frequency magnetic permeability can be obtained in that direction by arranging it to be axial. When used in the direction of the hard axis of magnetization, the response to changes in the external magnetic field is mainly caused by the rotational axis of magnetization, resulting in high high-frequency magnetic permeability.

Known methods for imparting such specific anisotropy to a magnetic thin film include evaporation in a magnetic field, sputtering in a magnetic field, and heat treatment in a magnetic field after film formation. At this time, the direction of the magnetic field is directed in the direction that should become the axis of easy magnetization. In addition, if the anisotropy imparted by these methods is too large and the magnetic permeability becomes low, first add a unidirectional magnetic field in the direction that should be the axis of easy magnetization, and then apply evaporation in a magnetic field or sputtering in a magnetic field. Alternatively, after the film is formed, heat treatment is performed in a magnetic field, and then heat treatment is performed in a rotating unidirectional magnetic field to reduce the magnitude of anisotropy.

The thin film magnetic core 1 of the thin film head usually has a shape as shown in FIG. 2, and is given anisotropy so that the track width direction 2 is the axis of easy magnetization. In manufacturing thin film heads, it is often necessary to provide anisotropy using the above-mentioned method after patterning a thin film magnetic core into the shape shown in FIG. In such a case, depending on the shape of the pattern of the magnetic thin film, the way in which the rotating unidirectional magnetic field is applied differs in the track width direction and in the direction perpendicular to the track width. As an extreme example, if the track width is extremely narrow, no magnetic field may be applied in the track width direction, and the direction of easy magnetization may be perpendicular to the track width.

The reason for this is the length W of the magnetic thin film pattern in the trunk width direction.
This is because the magnitude of the demagnetizing field in the track width direction and the direction perpendicular to the track width direction differs because the track width and the length W2 in the perpendicular direction differ, and the magnitude of the magnetic field effectively applied to the magnetic thin film differs. .

Zunawaji, if the strength of a rotating unidirectional magnetic field applied from the outside is defined as the magnetic field strength effectively applied to the H1 magnetic thin film as Hff, then in the track width direction, in the direction perpendicular to the track width, approximately Reff = H-4yrMs- -2w2. Here, t is the thickness of the magnetic thin film, and 4πMs is the saturation magnetization of the magnetic thin film. Like the magnetic core of a normal thin film head lol
, < w2, then He ff, (Heff2
As a result, the rotating unidirectional magnetic field no longer applies uniformly to the magnetic thin film pattern. For this reason, the anisotropy initially imparted in the trunk width direction by heat treatment in a unidirectional magnetic field may disappear, or the anisotropy size may be reduced to reduce the anisotropy and improve magnetic permeability. )・Rolls may become difficult.

Problems to be Solved by the Invention With the prior art, it has been difficult to provide a thin film magnetic core with a pattern such as that used in a thin film head with such anisotropy as to provide high magnetic permeability at high frequencies.

The only way to solve the problem is to perform heat treatment by simultaneously applying a fixed unidirectional magnetic field and a rotating unidirectional magnetic field within the film plane of the magnetic thin film pattern.

A fixed, unidirectional magnetic field is applied in a particular direction of the pattern of thin film cores. By making the magnitude of this magnetic field greater than or equal to the magnitude of the demagnetizing field generated by the magnetic thin film pattern, the magnetization within the magnetic thin film pattern is directed in the direction of the applied magnetic field. Furthermore, if a separately rotating unidirectional magnetic field is superimposed and applied, a fixed unidirectional magnetic field is applied, regardless of the change in the effective magnetic field applied to the magnetic thin film pattern due to the difference in the magnitude of the demagnetizing field depending on the shape of the magnetic thin film pattern. A magnetic field having a peak in the direction of the magnetic field is effectively applied to the magnetic thin film pattern.

When heat treatment is performed in such a magnetic field, the easy axis of magnetization is mainly in the direction of the fixed magnetic field, and the anisotropy is slightly dispersed around this axis.

Embodiment FIG. 1 shows an embodiment of the present invention. In the figure, reference numeral 1 denotes a thin film core of a thin film head made of a magnetic thin film. Also,
3 is a fixed unidirectional magnetic field H8, which is applied in the track width direction 2. Furthermore, 4 is a rotating unidirectional magnetic field HR.

The effect of this will be explained below using FIG.

A unidirectional magnetic field Hs fixed in the X direction in Fig. 3 is applied, and a unidirectional magnetic field HR rotating around the origin O is further applied.
is added. When H8 and HR are combined, the tip of the combined magnetic field HT moves on the circumference of the radius HR centered on the coordinate point (Hs, O). That is, in the X direction, Hs at maximum
+ While there is a period when the unidirectional magnetic field of HR is applied,
No unidirectional magnetic field is applied in the X direction at all. When such a magnetic field is applied to the magnetic thin film pattern, the magnetization within the magnetic thin film vibrates so as to be tilted in the ±yX direction with the X direction as the center. Therefore, when such a heat treatment in a magnetic field is performed, anisotropy is imparted, which has an axis of easy magnetization mainly in the X direction, with the anisotropy slightly dispersed around this axis. Therefore, when used in the X direction, a high high-frequency magnetic permeability can be obtained without causing a decrease in magnetic permeability due to excessive availability.

Furthermore, it is also possible to control the magnitude of anisotropy imparted by changing the magnitude of HR. That is, when HR is small, H8 becomes dominant and the anisotropy imparted becomes large. When HR is large, HR is dominant and the anisotropy imparted becomes small.

Conventional technology requires evaporation in a magnetic field, sputtering in a magnetic field, and heat treatment in a magnetic field with a fixed unidirectional magnetic field after film formation before heat treatment in a magnetic field with a rotating unidirectional magnetic field. According to the invention, this is no longer necessary.

In the present invention, the characteristics of the present invention are more fully exhibited in materials that can be effectively imparted with anisotropy by heat treatment in a magnetic field after film formation is completed. Therefore, rather than materials such as permalloy and sendust, which are difficult to impart anisotropy to unless a magnetic field is applied during film formation, it is preferable to use materials such as amorphous alloys, which easily rearrange atoms when heat treated in a magnetic field. It is desirable to practice the invention.

Next, specific examples will be described.

After forming a Go-Nb-Zr amorphous alloy magnetic thin film by sputtering, a magnetic thin film pattern as shown in FIG. 1 was formed using lithography technology. Thereafter, the above magnetic field was applied at a predetermined heat treatment temperature. The track width of the magnetic thin film pattern is 507 zm, the film thickness is 5 μm, and the saturation magnetization is 12K.
G, and the magnitude of the demagnetizing field in the track width direction is 1.2K.
Since it is about Oe, the size of Hs is 1.5KOe
And so. Further, the size of HR was set to 0.5 KOe. The above heat treatment in a magnetic field made it possible to impart anisotropy with an axis of easy magnetization in the track width direction.

Furthermore, a magnetic thin film pattern of the same shape is
．． When heat treatment was performed by applying a magnetic field with an HR of 1.5 KOe and an HR of 1.5 KOe, smaller anisotropy than the former could be imparted in the track width direction.

The electromagnetic conversion characteristics of a thin film head using a thin film magnetic core manufactured by performing heat treatment in a magnetic field as described above had good high frequency characteristics.

Effects of the Invention According to the present invention, after patterning a magnetic thin film, the direction and magnitude of magnetic anisotropy can be set to a desired value, and a thin film head with excellent high frequency characteristics can be produced using such a thin film core. can get.

[Brief explanation of the drawing]

FIG. 1 is a plan view illustrating a heat treatment method for a magnetic thin film in one embodiment of the present invention, FIG. 2 is a perspective view showing a thin film magnetic core, and FIG. 3 is a diagram showing the state of a magnetic field in this embodiment. It is. 1... Thin film magnetic core, 2... Trap and width direction, 3... Fixed unidirectional magnetic field, 4...
...Rotating unidirectional magnetic field. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 I -- Thin y @ 1; Width 1 No. Figure 3

Claims (4)

[Claims] (1) A method for heat treatment of a magnetic thin film, characterized in that heat treatment is carried out while simultaneously applying a unidirectional magnetic field fixed within the film plane of a magnetic thin film pattern and a unidirectional magnetic field rotating within the film plane. (2) The method for heat treatment of a magnetic thin film according to claim 1, wherein the magnitude of the fixed unidirectional magnetic field is approximately equal to or greater than the magnitude of the demagnetizing field generated by the magnetic thin film pattern. (3) Claim 1, characterized in that the magnitude of anisotropy imparted to the magnetic thin film pattern is controlled by changing the magnitude of the rotating unidirectional magnetic field.
A method for heat treatment of a magnetic thin film as described in . (4) The method for heat treatment of a magnetic thin film according to claim 1, wherein the magnetic thin film is an amorphous alloy.