JPH0648525B2 - Perpendicular magnetic recording / reproducing magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an improvement of a recording / reproducing head for perpendicular magnetic recording.

[Summary of the Invention] The present invention provides a main magnetic pole film of a magnetic recording head for perpendicular magnetic recording with a notch at the end portion in the track width direction.
By fixing the magnetic anisotropy of the main magnetic pole film, the reproduction output of the head can be stabilized and the reproduction efficiency can be improved.

[Prior Art] In the conventional read / write head for perpendicular magnetic recording, the track end of the main magnetic pole film is machined or etched to be a straight line as shown in FIGS. 4 (i) and (ii). It was

In the magnetic head for perpendicular magnetic recording, the main magnetic pole film is usually subjected to heat treatment or the like so that its easy axis of magnetization is in the track width direction.

The reason for providing such magnetic anisotropy will be described below.

If the magnetic flux flows from the recording medium to the main magnetic pole film if the longitudinal direction is set as the easy magnetization axis, the magnetic moment of the main magnetic pole film flows due to the domain wall motion because the direction of the flowing magnetic flux and the direction of the easy magnetization axis match. Try to match the direction of the magnetic flux. As is well known, when domain wall movement occurs, Barkhausen noise is generated, and the reproduction output is apt to be unstable because the domain wall movement is not reproducible. Moreover, since the frequency response of the domain wall movement is poor, the reproduction efficiency of the high frequency signal is low.

On the other hand, if the track width direction is the easy axis of magnetization,
Since the direction of the flowing magnetic flux and the direction of the hard axis coincide with each other, the magnetic moment of the main magnetic pole film tends to coincide with the direction of the flowing magnetic flux by rotating. In this case, since the domain wall movement does not occur, the above phenomenon does not occur.

For this reason, the axis of easy magnetization of the main magnetic pole film is made to be in the track width direction.

When magnetic anisotropy is imparted to the main magnetic pole film in this way, the magnetic domain structure formed by alternating-current magnetization of the main magnetic pole film has magnetostatic energy due to generation of magnetic poles, domain wall energy, and return magnetic domain (where the magnetic moment is the main magnetic pole). The structure is such that the total sum of the magnetic anisotropy energies stored in the length direction of the film, that is, the region facing the hard axis direction) is minimized. Therefore, when the shape of the main magnetic pole film is made the same and the anisotropic magnetic field Hk is changed, the magnetic domain structure is changed as shown in (i) and (ii) of FIG. (However, here, the relationship between the length L of the portion of the main magnetic pole film held by the non-magnetic material and the track width W is such that L is necessary to some extent in consideration of the life of the main magnetic pole.
Wants to be as small as possible for high density recording,
Consider the case of L> W. As can be seen from these figures, when the anisotropic magnetic field Hk is small, the domain wall is reduced and the size of the return magnetic domain is large as compared with the case where Hk is large. This is because the magnetic anisotropy energy per unit volume of the magnetic film becomes smaller as the anisotropic magnetic field Hk becomes smaller, and thus the total energy becomes smaller when the reflux magnetic domain is made larger.

By the way, the reproduction efficiency of the head is better as the magnetic permeability μ is larger.
Since the smaller the anisotropic magnetic field Hk is, the larger μ is, the smaller the Hk is, the better the reproduction efficiency is. However, as described above,
The reflux magnetic domain becomes larger. Since the magnetic moment in the reflux magnetic domain is saturated due to the increase of anisotropic energy, it has a poor response to the external magnetic field. That is,
If the anisotropic magnetic field Hk is made too small, the reflux magnetic domain becomes large and the reproducing efficiency deteriorates.

This means that there is an anisotropic magnetic field Hk that maximizes the reproduction efficiency when the shape of the main magnetic pole film is fixed.

Next, if the track width W is reduced while keeping the anisotropic magnetic field Hk and the length L of the main magnetic pole film constant, the demagnetizing field in the track width direction increases and the magnetostatic energy increases. Therefore, the reflux magnetic domain becomes large. That is, the reproduction efficiency becomes poor.

As described above, the relationship between the reproduction efficiency and the anisotropic magnetic field Hk is calculated by the track width W.
Is shown as a parameter, it becomes as shown in FIG.

In the conventional technique, when a head having a narrow track width is produced, the reproducing efficiency is lowered if the track width W is reduced while the anisotropic magnetic field Hk is constant (reproducing efficiency is Q from point P in FIG. 3).
4) (i), the anisotropic magnetic field Hk is increased.
As in i), the area ratio of the reflux magnetic domain was made small (regeneration efficiency changed from point Q to point R).

[Problems to be Solved by the Invention] However, such a method of increasing the anisotropic magnetic field Hk causes a decrease in reproduction efficiency as can be seen by comparing the reproduction efficiency at the R point and the reproduction efficiency at the P point.

Therefore, the present invention does not reduce the magnetic permeability μ, that is,
The purpose is to reduce the size of the reflux magnetic domain while keeping the anisotropic magnetic field Hk small.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a magnetic head for perpendicular magnetic recording / reproducing in which a length of a portion of a main magnetic pole film held by a non-magnetic substrate is formed larger than a track width. In the above, one or more notches are provided at the end of the main magnetic pole film portion in the track width direction.

[Operation] When the magnetic moment in the vicinity of the above-mentioned cut portion is oriented in the length direction of the main magnetic pole film, magnetization is generated, and the magnetostatic energy is increased as compared with the case where there is no cut, and the magnetic moment is reduced in order to reduce this energy. Since the return magnetic domain becomes smaller toward the track width direction, the reproduction efficiency is improved.

Embodiment of the Invention Next, an embodiment of the present invention will be described with reference to the drawings.

An embodiment of a recording / reproducing head for perpendicular magnetic recording according to the present invention will be described with reference to FIG. 1. The head includes a main magnetic pole film 1 made of a soft magnetic thin film and an adhesive 6 so as to sandwich the soft magnetic thin film 1. It is composed of two soft magnetic substrates 2 and 3 and two non-magnetic substrates 4 and 5 and a winding 7 which are bonded together by.

FIG. 2 shows a portion of the head of FIG. 1 from which the soft magnetic substrate 3, the non-magnetic substrate 5, the adhesive 6 and the winding 7 are removed, and particularly the shape of the main magnetic pole film 1 is shown in perspective.

The feature of the present invention resides in the shape of the main magnetic pole film 1. One or more of the main magnetic pole film is provided at the end portion in the track width direction of the portion sandwiched between the non-magnetic substrates 2 and 3 as shown in FIG. The notch 8 is provided. The notches 8 can be formed by forming the soft magnetic thin film 1 on the entire surface by, for example, a sputtering method and then removing unnecessary portions by etching.

Next, the operation of the present invention will be described.

In the conventional technique, the length L of the main magnetic pole film 1 and the track width W are L
It is assumed that, when a head having a shape such that> W is created, the anisotropic magnetic field Hk is set to a certain magnitude and the magnetic domain structure shown in FIG. 4 (i) is obtained. As described in the section of the problem of the prior art, if the return magnetic domain is too large, the reproduction efficiency is lowered. Therefore, in order to reduce the return magnetic domain, the anisotropic magnetic field Hk is increased in the prior art to increase the anisotropic magnetic field Hk in FIG. The magnetic domain structure shown in ii) was used.

The present invention is characterized in that the notch 8 is made at the end of the track at an interval of d as described above without increasing the anisotropic magnetic field Hk. When a notch is made, when the magnetic moment near the notch is oriented in the length direction, magnetization can be made at the notch, so the magnetostatic energy is increased compared to when the magnetic moment is oriented in the length direction without the notch. It will be. Therefore, in order to reduce the magnetostatic energy, the magnetic moment tends to move in the track width direction. That is, the return magnetic domain becomes smaller than that when there is no cut.

The larger the number of cuts, that is, the smaller the gap d between the cuts, the larger the increase in the magnetostatic energy due to the cuts. Therefore, by making d small to some extent, the return magnetic domain can be made smaller. A magnetic domain structure as shown in FIG. 4 (iii) can be obtained. That is, by making a cut, the return magnetic domain can be reduced without increasing the anisotropic magnetic field Hk as in the conventional technique.

[Effects of the Invention] As described above, according to the present invention, the return magnetic domain can be reduced even when the anisotropic magnetic field Hk is reduced. That is, it is possible to prevent the reproduction efficiency of the head from being lowered by the return magnetic domain. FIG. 5 compares the relationship between the anisotropic magnetic field Hk of the magnetic head according to the present invention and the reproducing efficiency with that of the magnetic head according to the prior art. However, it is assumed that the length L of the main magnetic poles of both heads and the track width W are the same. As shown in this figure, the reproducing efficiency of the magnetic head according to the present invention is higher than that of the prior art by the anisotropic magnetic field Hk.
It is understood that when the values are equal, the reflux efficiency is improved due to the small reflux magnetic domain.

Next, assuming that the reproducing efficiency of the conventional magnetic head having the magnetic domain structure of FIG. 4 (i) is at the position indicated by point A in FIG.
In the prior art, the anisotropic magnetic field Hk is increased so that the magnetic field is located at the point B in FIG. However, if the present invention is applied, the regeneration efficiency at point A in FIG. 5 can be increased to the regeneration efficiency shown at point C. Further, by using the present invention and the prior art together, it is possible to increase the reproduction efficiency shown at point D,
It is possible to obtain a reproducing efficiency higher than the reproducing efficiency (point B) of the magnetic head only by the conventional technique.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of a magnetic head using the present invention, and FIG. 2 shows the shape of the main magnetic pole film 1 which is a characteristic part of the present invention in which the substrate on one side of the head of FIG. 1 is removed. FIG. 3 is a perspective view showing the anisotropic magnetic field H of the conventional magnetic head.
FIG. 4 is a diagram showing the relationship between k and the reproduction efficiency using the track width W as a parameter. FIG. 4 shows an example of the shape of the tip of the main magnetic pole film and a domain pattern of the prior art, and the shape of the tip of the main magnetic pole film according to the present invention. Front view showing examples and magnetic domain pattern examples,
FIG. 5 is a diagram comparing the relationship between the anisotropic magnetic field Hk of the magnetic head according to the present invention and the reproducing efficiency with that of the conventional magnetic head. 1 ... Main magnetic pole film, 2, 3 ... Soft magnetic substrate, 4, 5 ... Non-magnetic substrate 6 ... Adhesive, 8 ... Notch.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isamu Horiuchi 5329 Shimosuwa-cho, Suwa-gun, Nagano Sankyo Seiki Seisakusho Co., Ltd. (56) Reference JP-A-58-199422 (JP, A)

Claims (1)

[Claims] 1. A perpendicular magnetic recording / reproducing magnetic head in which a length of a portion of a main magnetic pole film held by a non-magnetic substrate is larger than a track width, and an end portion of the main magnetic pole film portion in a track width direction. A magnetic head for perpendicular magnetic recording / reproducing, characterized in that one or more notches are provided in the.