JPS63253503A - Perpendicular magnetic field impressing device - Google Patents

Abstract

PURPOSE:To substantially obviate a decrease in a perpendicular magnetic component and to decrease eddy current loss by using a multi-layered structural body consisting of thin magnetic films and nonmagnetic films having an insulating characteristic as a magnetic pole and disposing the magnetic pole in such a manner that a horizontal magnetic field is perpendicular to the multi-layered films of the multi-layered structural body. CONSTITUTION:The magnetic pole consisting of the multi-layered structure is disposed to a perpendicularly magnetized medium 5. This multi-layered structural body is laminated with plural layers of the soft magnetic films 1 and the nonmagnetic layers 2. The multi-layered films of this multi-layered structural body face the perpendicularly magnetized medium 5. A coil 3 is wound around the magnetic pole consisting of the multi-layered structural body. The soft magnetic films 1 are formed of amorphous Zr-Co and the nonmagnetic layers of SiO2 by a sputtering method. The horizontal magnetic field 4 is impressed to the multi-layered film planes of unidirectional multi-layered structural body so that the film planes are held perpendicular to the horizontal magnetic field. A self-demagnetizing field acts in the direction perpendicular to the film plane and the inclination of a spin in the direction HM when a DC magnetic field HM is applied to the films is suppressed and, therefore, the perpendicular magnetic field component is hardly decreased. Since the magnetic films are thin, the eddy current loss is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application> The present invention relates to improving the performance of a magnetic field applying device in magneto-optical recording using a magnetic field modulation method and a magnetic head in perpendicular magnetic recording.

<Conventional Technologies and Problems> Magneto-optical recording has been actively researched because it promises higher recording density than current magnetic disks, and because information can be rewritten compared to optical disks. The principle of magneto-optical recording and reproducing is that a perpendicularly magnetized film is applied with a direct current external magnetic field in the direction you want to record, and then a laser is applied to the area where you want to write and heat is applied. As the temperature of the surface approaches the Curie temperature and the perpendicular magnetic anisotropy energy decreases, the magnetization is reversed in the direction of the external magnetic field. Recording is performed by maintaining this inversion. Further, when performing reproduction, the difference in magnetization direction due to the Kerr effect is read out by the difference in Kerr rotation angle (θK). That is, by passing the difference in the polarization plane of the reflected light (polarized light) through an analyzer, the magnetization direction of the medium can be detected as a difference in light intensity.

The principle of magneto-optical recording is as described above (however, in magneto-optical recording, recording is performed using light and a magnetic field, but there are also differences between the optical modulation method and the magnetic field modulation method due to the difference in the object of modulation. In other words, as shown in Figure 5,
Optical modulation involves applying an external magnetic field (bias magnetic field) in the opposite direction to a medium that has already been magnetized in a certain direction, converting information as flashing light, and recording by reversing the magnetization of the area that is hit by the light. In this method, laser light is continuously irradiated, and information is added as a reversal of the bias magnetic field, as in normal magnetic recording, and as the medium cools, the magnetic field is recorded as a sequence of magnetization reversals according to the direction of the bias magnetic field. There is a modulation method.

In these optical modulation methods and magnetic field modulation methods, it is necessary to create a fairly large magnetic field in the film thickness direction. In particular, the magnetic field modulation method requires a large magnetic field of tens to hundreds of 01, and a high frequency is required to increase the writing speed. Become. Specifically, a head for applying a magnetic field used for recording using the magnetic field modulation method is composed of a coil or a coil having a magnetic core for obtaining an alternating magnetic field (recording signal magnetic field) perpendicular to the medium surface. If the distance between the medium surface and the head is set to be several hundred or more, and a magnetic field of several +0 or more is applied to the medium surface, the cross-sectional area of the head must be on the order of square millimeters, and Mn -Z, it is necessary to use a magnetic core with high magnetic permeability such as ferrite.

The impedance of the 5-wire increases due to the increase in size and the use of a high permeability magnetic core, so when driving with AC, the drive current increases and the heat generated due to it, and the recording magnetic field is emitted spatially widely, so it is not suitable for servo drives. There were problems such as incomplete head position determination due to the effect on the voice coil of the head.

In other words, the perpendicular magnetic field applied from the outside requires a large value regardless of whether the optical modulation method or the magnetic field modulation method is used, and the magnetic field modulation method in particular poses difficulties in terms of M configuration.

In order to reduce the magnitude of such a vertical magnetic field, the use of a horizontal magnetic field has been considered. In other words, for a film that has uniaxial magnetic anisotropy in the direction perpendicular to the film surface, such as a magneto-optical medium,
The reversal of magnetization is thought to follow the so-called -pre-rotation mode, in which the spins are aligned and rotate in one stroke.

(Kobayasbi, 'r, Jpn, J people pp
1. phy, 20.1981. pp. 2089) It has been proposed that in such a film, if a magnetic field 1 is also applied parallel to the film surface, the magnetic field required to reverse the magnetization in the perpendicular direction can be reduced.

However, when viewed as a magnetic field applying device, a head configured to apply a magnetic field simultaneously in parallel and perpendicular directions to the film surface has not been devised in the past. I mean,
The soft magnetic material itself used as the magnetic pole is also magnetized in the direction of the magnetic field when a magnetic field parallel to the medium surface is applied, substantially reducing the magnetic permeability of the magnetic pole.

In other words, the vertical magnetic field is less likely to be excited.

A similar situation also holds true in so-called perpendicular magnetic recording heads, which magnetize the medium in a direction perpendicular to the film surface in magnetic recording that does not use light.

In view of the above-mentioned problems, the present invention provides a vertical magnetic field applying device for information writing, which applies a vertical magnetic field while applying a horizontal magnetic field to a film surface.

(Means for Solving the Problems) The present invention achieves the above object by applying a perpendicular magnetic field in a direction perpendicular to the film surface of a perpendicular magnetic recording medium by existing in a horizontal magnetic field parallel to the film surface. In the vertical magnetic field applying device, a multilayer structure of a magnetic thin film and an insulating nonmagnetic film is used as a magnetic pole, and the magnetic pole is arranged so that the horizontal magnetic field is perpendicular to the surface of the multilayer in the multilayer structure. It is characterized by

EMBODIMENTS> The present invention will now be described in detail with reference to FIGS. 1 to 4.

In FIG. 1, a magnetic pole made of a multilayer structure is arranged for a perpendicularly magnetized medium 4. This multilayer structure has a multilayer structure in which a large number of soft magnetic films 1 and nonmagnetic layers 2 are laminated. The multilayer film of this multilayer structure faces the perpendicular magnetization medium 4. A coil 3 is wound around this multilayered magnetic pole. In this case, 100 layers of an 8% Zr-92% CO amorphous film with a thickness of 0.5μ as the soft magnetic film and an SiO2 film with a thickness of 1μ as the nonmagnetic layer were formed by sputtering, and the coil was An example is one in which the wire is wound 50 times.

On the other hand, a horizontal magnetic field is applied perpendicularly to the film surfaces of the multilayers of the multilayer structure. That is, the multilayer structure is arranged so that the film surface is perpendicular to the horizontal magnetic field. In this case, the external magnetic field, which is a horizontal magnetic field, may be any uniform DC magnetic field, and a magnetic field generated by a permanent magnet or a Helmholtz coil is used. Here, the horizontal magnetic field is applied perpendicularly to the film surface so that the magnetization and self-demagnetization in the film thickness direction of the soft magnetic film 1 cancel each other out, suppressing the spin rotation of the magnetic moment caused by the external magnetic field. This is to minimize the influence of external magnetic fields.

Here, the distance between the medium 5 and the magnetic pole tip was set to 500 degrees, and the magnetic field strength (H) in the direction perpendicular to the medium at a location 500 degrees away from the center of the magnetic pole tip surface was measured.
and horizontal magnetic field H8. Note that H2 is H, = OO,
It is normalized by the value at the time of .

In FIG. 2, H is 1000. The decrease in H is constant within the experimental error range up to approximately

That is, by using such a structure, it is possible to apply a signal magnetic field (alternating current) in the perpendicular direction and also apply a direct current magnetic field in the horizontal direction to a perpendicularly magnetized film such as a magneto-optical recording medium.

In the direction perpendicular to the film surface, the film's self-demagnetizing field (4π
M, , M, : @ Spontaneous magnetization of the magnetic film) acts, so when the town is added, the spin is suppressed from tilting in the direction of the town. In the range where is small (H, << 4πM,), H hardly decreases.
Since 2 is proportional to M and l, the above result is obtained.

In the case of this example, since the thickness of the magnetic pole is as thick as 150 tones, it is suitable as a magnetic field application device for writing using a magnetic field modulation method in magneto-optical recording. If the thicknesses of the layer and the nonmagnetic layer are reduced, it is suitable as a grass type magnetic head for perpendicular magnetic recording.

Figures 3 and 4 show other structural examples of magnetic poles.
The figure shows a closed magnetic path structure in which a magnetic path for returning magnetic flux is formed, and unlike the example in FIG. 1, magnetic flux is generated only on the medium side, and the magnetic flux utilization efficiency is good. Furthermore, in FIG. 4, the magnetic flux may be generated by a relatively large electromagnet (auxiliary magnetic pole) placed with the medium sandwiched between them, without winding a coil around the magnetic pole itself. In this case, if the auxiliary magnetic pole 6 is not made of a multilayer structure, the horizontal magnetic field applied to the auxiliary magnetic pole 6 needs to be set to be small enough to be practically acceptable. However, since the auxiliary magnetic pole 6 is separate from the recording magnetic pole, a large current may be passed therethrough to generate a strong magnetic force.

Furthermore, the structures shown in FIGS. 3 and 4 may be combined. In any case, by making the magnetic pole a multilayer structure of a magnetic thin film and a nonmagnetic film, and applying a uniform magnetic field perpendicular to the film surface, in addition to the signal magnetic field perpendicular to the medium,
Horizontal DC magnetic fields can be superimposed.

<Effects of the Invention> As explained above, the vertical magnetic field application device according to the present invention is shaped to apply a DC magnetic field (H,) perpendicularly to the magnetic pole surface, so that the vertical magnetic field component (H2) generated from the magnetic pole is
will hardly decrease if the town is small. Furthermore, even when H is a high-frequency magnetic field, the thin magnetic film has the effect of reducing eddy current loss.

[Brief explanation of the drawing]

Figures 1 to 4 show an embodiment of the present invention, where Figure 1 is a simplified perspective view of a multilayer structure, Figure 2 is a characteristic diagram showing the relationship between vertical and horizontal magnetic fields, and Figure 3 is a closed magnetic field. FIG. 4 is a perspective view of the path structure, FIG. 4 is a perspective view of the case with an auxiliary magnetic pole, and FIG. 5 is an explanatory diagram of two magneto-optical recording systems. In the figure, 1 is a soft magnetic film, 2 is a nonmagnetic film, 4 is a uniform horizontal magnetic field, and 5 is a vertically magnetized medium. Patent applicant: Agent of Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] A vertical magnetic field applying device that exists in a horizontal magnetic field parallel to a film surface of a perpendicular magnetic recording medium and applies a perpendicular magnetic field in a direction perpendicular to the film surface, comprising: a magnetic thin film and an insulating non-magnetic film; A vertical magnetic field applying device characterized in that a multilayer structure including a film is used as a magnetic pole, and the magnetic pole is arranged so that the horizontal magnetic field is perpendicular to the surface of the multilayer in the multilayer structure.