JPS6372102A - Thin film magnetic circuit - Google Patents

Abstract

PURPOSE:To obtain a thin film core with excellent radio frequency characteristics which provides excellent results when it is employed in a thin film magnetic head and a thin film transformer by a method wherein a thin film magnetic circuit which is composed of an annular thin film conductor layer and annular thin film cores provided adjoining to both the surfaces of the conductor layer is employed. CONSTITUTION:An annular conductor layer 11 is provided so as to be sandwiched by annular cores 10 composed of thin magnetic films. When these cores 10 are annealed in a magnetic field, the AC magnetic field is applied along the direction 12 perpendicular to the thin magnetic film surface. After those cores 10 are formed by a lithography technology or the like, the AC magnetic field is applied to the cores at a predetermined annealing temperature. At that time, the magnetic field intensity is selected to be as large as possible but without exceeding the extent of 4piMs wherein Ms denotes the saturation magnetization of the core. In this process, the magnetic core films are not vertically magnetized because of a reverse magnetic field. On the other hand, the AC magnetic field induces an AC current along the annular path in the conductor layer 11 and the induced current produces an AC magnetic field 13. With this constitution, the distribution of radial easy-to-magnetize axes can be obtained and any parts of the flux flow paths 7 operate along the difficult-to-magnetize axes so that a core with excellent radio frequency operation can be obtained.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a thin film magnetic core, and in particular, it is an object of the present invention to provide a thin film magnetic core with excellent high frequency characteristics that can be used in thin film magnetic heads and thin film transformers to obtain good results. .

BACKGROUND OF THE INVENTION Conventionally, in magnetic cores used at high frequencies, especially in magnetic cores formed of thin films, the axis of easy magnetization of the magnetic thin film 3 is aligned in a direction 2 approximately perpendicular to the direction 1 in which magnetic flux flows, as schematically shown in FIG. It is known that if the direction 1 in which the magnetic core is used becomes the axis of difficulty in magnetization, high high frequency magnetic permeability can be obtained in that direction. This is because when used in the direction of the difficult axis of magnetization, the response to changes in the external magnetic field is mainly performed by rotation of magnetization, resulting in high high frequency magnetic permeability.

Known methods for imparting such specific anisotropy include evaporation in a magnetic field, sputtering in a magnetic field, and annealing 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.

On the other hand, magnetic cores used in magnetic heads, transformers, etc. are usually formed in a substantially ring shape because the magnetic flux always forms a loop. If such a ring-shaped magnetic core is, for example, the magnetic core of a thin-film magnetic head configured as shown in FIG. 8 (the coil is not shown), if anisotropy is imparted by the magnetic field 5 in a single direction, In any part of the magnetic flux flow 6, the magnetic core can be operated in the direction of the hard axis, which is very advantageous.

However, as shown in FIG. 9, in the case of a magnetic core formed in a loop pattern within one thin film formation surface, in order to obtain movement in the direction of the difficult magnetization axis at all positions along the magnetic flux path, 8, it is necessary to have a radial easy axis distribution of magnetization. However, it is not easy to provide such anisotropy using ordinary magnetic field application means. A known method for solving this problem is to provide an axis of easy magnetization in a direction 9 perpendicular to the film surface of the magnetic core as shown in FIG. In this way, motion in the direction of the hard magnetization axis can be obtained over all seven paths. However, this method has a problem in that it is difficult to apply an effective magnetic field against an extremely large demagnetizing field in a direction perpendicular to the film surface to impart desired anisotropy.

Problems to be Solved by the Invention As described above, it is difficult with the prior art to provide such anisotropy as to obtain high magnetic permeability at high frequencies to a thin film magnetic core of the form shown in FIG. 9.

Means for Solving the Problems In the present invention, a ring-shaped thin film conductor layer and a ring-shaped thin film magnetic core are provided adjacent to each other on at least one surface of the conductor layer, and when annealing the ring-shaped magnetic core, An alternating magnetic field is applied in a direction substantially perpendicular to the thin film surface.

The AC magnetic field during operational annealing is applied perpendicularly to the thin film surface of the ring-shaped magnetic core, but due to the large demagnetizing field in the film surface direction, the magnetic field applied substantially perpendicular to the film surface of the magnetic core can be ignored. However, the applied alternating current magnetic field inevitably induces a wave in the ring-shaped conductive layer by electromagnetic induction, and the magnetic field generated by this alternating current acts to magnetize the ring-shaped magnetic core in the radial direction. Therefore, if annealing is performed under such conditions, the ring-shaped magnetic core can have a radial distribution of easy magnetization axes, that is, all paths along the flow of magnetic flux can be made to operate in the difficult magnetic direction.

Embodiment FIG. 1 shows an embodiment of the present invention. 10 in the same figure
is a ring-shaped magnetic core made of a magnetic thin film.

Further, 11 is a ring-shaped conductor layer formed to be sandwiched between the ring-shaped magnetic cores. Reference numeral 12 denotes the direction of an alternating current magnetic field to be applied when annealing the magnetic core as described above in a magnetic field, and this is a direction perpendicular to the surface of the magnetic thin film. Appropriate thin film technology,
After forming a magnetic core as shown in FIG. 1 using the ring graphie technique, the above-mentioned alternating current magnetic field is applied at a predetermined annealing temperature.

At this time, the magnitude of the magnetic field is made as large as possible without exceeding 4πMs, where Ms is the saturation magnetization of the magnetic core. At this time, the magnetic core membrane is not substantially magnetized in the perpendicular direction due to the demagnetizing field. On the other hand, the alternating magnetic field
This induces an alternating current to flow through it along its ring-shaped path, which in turn produces an alternating magnetic field as shown in FIG.

Since the direction of this alternating magnetic field is distributed approximately radially in the ring-shaped magnetic core, a distribution of radial easy magnetization axes as shown in FIG. The movement is in the axial direction. In this way, a magnetic core with excellent high frequency operation can be obtained.

Considering only the direction of the magnetic field generated from the ring-shaped conductive layer, the magnetic core 10 does not need to have a two-layer structure as shown in FIGS. It is desirable because it is easy to apply a magnetic field, and even after the annealing is completed, the upper and lower moments form a pair, making it stable in terms of energy and making it possible to maintain a more stable radial moment distribution.

As is clear from the above invention, it is not practical to use the method of imparting anisotropy by forming a film in a magnetic field in the present invention.
The features of the present invention are best exhibited in materials that can be effectively imparted with anisotropy by annealing in a magnetic field after film formation is completed. Therefore, materials such as Permalloy and Sendust, which are difficult to impart anisotropy to without applying a magnetic field during film formation, can be easily anisotropic by annealing in a magnetic field near the Curie point after film formation, such as amorphous magnetic materials. It is desirable to practice the present invention using materials that can impart properties.

FIG. 5 shows an embodiment in which the present invention is applied to a thin film transformer. In the figure, 10 is a ring-shaped thin film magnetic core, 11 is a ring-shaped conductor layer, and the former constitutes a magnetic circuit of a transformer. Again 1
6 is a primary winding of the transformer, and 16 is a secondary winding of the transformer, both of which are formed using thin film technology so as to interlink with the magnetic core 10 described above.

After the film formation is completed in this manner, annealing is performed while an alternating magnetic field is applied in a direction perpendicular to the film surface, as described in FIG. 1. The annealing temperature is set to a predetermined temperature for the material used for the thin film core. By doing so, the high frequency characteristics of the magnetic permeability along the direction of the signal magnetic flux flowing through the magnetic circuit of the transformer are improved, and a transformer with excellent high frequency characteristics can be obtained.

FIG. 6 shows an embodiment in which the present invention is applied to a so-called video type magnetic head. In the figure, reference numeral 17 denotes a magnetic helad core, which is formed in such a manner as to sandwich a conductive layer 18 therebetween. Reference numeral 19 denotes a front gap portion, and the left and right cores 17 are magnetically separated by a predetermined gap length at this portion, but the left and right conductor layers 18 are connected at this gap portion without being electrically disconnected. It is composed of The conductor layer 18 also exists in the pack gap portion 20.
are configured to be electrically connected.

Reference numeral 21 denotes a winding window, that is, the conductor layer 18 forms a ring-shaped conductor that uses the winding window as a medium heat source. When the magnetic herad core thus formed is annealed in an alternating current magnetic field in the direction 23 perpendicular to the core surface, the radial easy axis distribution of magnetization shown at 22 is obtained for the reason shown in FIG. As a result, high magnetic permeability can be obtained along the direction in which the signal magnetic flux flows in the head, and a magnetic head with excellent high frequency characteristics can be obtained.

Effects of the Invention According to the present invention, it is easy to impart magnetic anisotropy to any part of the ring-shaped thin-film magnetic core along the flow of magnetic flux so that the magnetic core moves in the direction of the difficult-to-magnetize axis. It can be used to form magnetic heads and transformers with excellent high frequency characteristics.

[Brief explanation of the drawing]

1 to 3 are respectively a perspective view, a sectional view, and a plan view of a thin film magnetic circuit according to an embodiment of the present invention, FIG. 4 is a sectional view of the same essential part, and FIGS. FIG. 6 is a perspective view showing still another embodiment of the present invention, FIG. 7 is a plan view explaining the conventional technique, and FIG.
This figure and FIG. 9 are perspective views of the same. 1o... Ring-shaped thin film magnetic core, 11...
Ring-shaped conductor layer, 12...Direction of application of alternating current magnetic field. Name of agent: Patent attorney Toshio Nakao and one other IO
- To Ringo K〉 1a Figure 2 Figure 47 Figure 5 Figure 9 Figure 6 Figure 7 - Figure 8 L Sea 1 Figure 9

Claims (3)

[Claims] (1) A thin film magnetic circuit comprising a ring-shaped thin film conductor layer and a ring-shaped thin film magnetic core disposed adjacent to at least one surface of the conductor layer. (2) The thin film magnetic circuit according to claim 1, characterized in that the thin film core is formed of an amorphous magnetic material. (3) The thin film magnetic circuit according to claim 1, characterized in that thin film magnetic cores are arranged on both sides of the conductor layer.