JPS6246418A - Bias impression type magnetic head - Google Patents

Abstract

PURPOSE:To increase the sensitivity of a bias type magnetic head and to reduce malfunction by providing the head with distribution increasing the amplitude of an AC magnetic field in accordance with a greater distance separated from a magnetic recording medium. CONSTITUTION:The bias type magnetic head is constituted of a bias magnetic field impressing magnetic pole 8, a bias magnetic field exciting coil 9, a head magnetic pole 1, a polarizing laser beam 6, and a magnetic recording medium 4. The head magnetic pole 1 is projected from the leading end surface of the magnetic field 8. To actuate the head magnetic pole 1, a high frequency current is supplied to the coil 9 and an AC bias magnetic field is impressed to the horizontal direction of the head magnetic pole surface. The distribution of the amplitude of the AC magnetic field is increased in accordance with the distance separated from the magnetic recording medium 4. Since a gradient is formed in the bias magnetic field, an area sensing a recording signal can be successively expanded on the head magnetic pole 1, so that the sensitivity of the head can be increased and malfunction can be reduced.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a magnetic storage device that has a high recording density and can obtain a sufficiently large reproduction output even when the amount of magnetic flux generated from the medium is reduced. It concerns a sensitive magnetic head.

(Prior Art) The principle of a magnetic head conventionally used in a magnetic recording device is as follows. A method (electromagnetic induction type) in which the magnetic flux generated from the magnetic recording medium is guided by a head magnetic pole with high magnetic permeability, and the time change in magnetic flux is detected as a voltage generated at both ends of a coil wound around the bed magnetic pole; The main method used was to change the direction of magnetization of the head pole depending on the magnetic field generated, and detect this change in magnetization using the magnetoresistive effect or the magneto-optical effect. In these heads, the magnetization of the head magnetic pole changes only by an amount that is balanced with the Zeeman energy due to the magnetic field generated from the medium.6 In other words, in terms of the operating mechanism, they can be classified as passive elements.

On the other hand, as a method of changing the magnetization of the head pole more than the change in magnetization caused by the magnetic field generated from the medium, a head to which a magnetic bias is applied has been proposed, such as Japanese Patent Application No. 58-87557.59-78357. This principle is the 8th
As shown in the figure, a magnetic thin film pattern with a single domain structure having uniaxial magnetic anisotropy is used as the head magnetic pole 1, and it is difficult to magnetize an alternating current magnetic field (bias magnetic field) 2 having an amplitude greater than the anisotropic magnetic field of the head magnetic pole. It adds to the direction. The magnetization 3 of the head magnetic pole is once saturated in the direction of difficult magnetization due to the bias magnetic field, but at the next moment, the bias magnetic field strength becomes 0, so that it rotates in the direction of easy magnetization 5. At this time, since only the magnetic field generated from the recording medium acts on the head magnetic pole as the driving force for magnetization rotation, in principle, the head magnetization is rotated by an infinitesimal magnetic field. This rotation of magnetization can be detected as a rotation of the polarization plane of the reflected light or transmitted light of the polarized light irradiated to the head magnetic pole, so that signal analysis can be performed. In addition,
6 is incident polarized light, and 7 is reflected polarized light.

(Problem to be Solved by the Invention) However, when the above head is actually operated, there are cases where the magnetization does not necessarily reverse in the direction of the signal magnetic field if the uniaxial magnetic anisotropy in the head magnetic pole is dispersed. This included problems such as the occurrence of Additionally, if an external magnetic field (disturbance) with a magnitude greater than the signal magnetic field is applied at the moment when the bias magnetic field strength becomes 0, the magnetization of the head magnetic pole will rotate in a direction close to the direction of the magnetic field of the disturbance, resulting in malfunction, etc. There was also a problem.

An object of the present invention is to provide an external alternating current magnetic field to the head magnetic pole.
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Add the field t6. :ni'r"". If the sensitivity is set to 1216
1. Disturbances, dispersion of magnetic anisotropy of "Do"7 material, etc. 1° 1j'''-6M!114'!&M'J>;a -1i
−6°2′<v*; b=hb=.

be.

(Means for Solving the Problems) A feature of the present invention for achieving the above object is that a head core made of a magnetic material having uniaxial magnetic anisotropy is faced to a magnetic recording medium, and the magnetic field generated from the magnetic recording medium is In a magnetic head that applies an alternating magnetic field from the outside to the head core in a substantially orthogonal direction and detects rotation of the magnetic field within the head core corresponding to recording on a magnetic recording medium, the amplitude of the alternating magnetic field varies depending on the distance from the magnetic recording medium. A bias application type magnetic head has a distribution that becomes stronger as the distance increases.

On the other hand, in the prior art, the bias magnetic field is uniformly applied to the entire head pole, and this point is the main difference from the present invention.

(Function) According to the present invention, the strength of the bias magnetic field applied to the head magnetic pole is such that when the bias magnetic field increases, the tip of the magnetic pole (the part near the medium) saturates last, while when the bias magnetic field decreases, the strength of the bias magnetic field applied to the head magnetic pole saturates last. It has a slope that decreases from the tip of the magnetic pole. Therefore.

Even if the bias magnetic field at the tip of the head becomes 4#yo and becomes sensitive to the signal magnetic field, the bias magnetic field is applied to most of the area of the head magnetic pole, so this area will not become unstable due to disturbance. do not have. In other words, the signal magnetic field is affected sequentially starting from the tip of the head. Therefore, a magnetic head that does not malfunction even when there is a disturbance or dispersion of magnetic anisotropy can be obtained.

(Embodiment) Fig. 1 shows an embodiment of the present invention, in which 8 is a magnetic pole for applying a bias magnetic field, 9 is a coil for excitation of a bias magnetic field, 1 is a head magnetic pole, 6 is a polarized laser beam, and 4 is a magnetic recording medium. . The head magnetic pole is arranged so as to protrude from the tip end surface of the bias magnetic field applying magnetic pole. To operate this, a high frequency current is passed through the bias magnetic field excitation coil, and an alternating current bias magnetic field is applied in the horizontal direction of the head magnetic pole surface. : As shown in Figure 2, the change in the amplitude of the AC bias magnetic field on the head pole surface becomes smaller toward the tip of the head pole. I bias magnetic field excitation current is large j ft 6314 case 1°""" tip part 7゛ last 1° saturation 5 ('ゞ ! The value of Ias magnetic field is less than the anisotropic magnetic field Hk of the head magnetic pole l k fJ !), - F12.
Ia xm*h<, wo, 1; "'°"""Tip part 7゛6 sequential 1""Lower J: 24 M area
:,′ expands.

Figure 3 shows the difference in operating mechanism between (a) the conventional bias magnetic field application method (uniform magnetic field) and (b) the bias magnetic field application method according to the present invention. When applying a magnetic field, when the bias magnetic field (Hb) applied to the head magnetic pole decreases, if a disturbance (Hi) is applied in the opposite direction in addition to the magnetic field from the recording medium (signal magnetic field 1Hs), Hb becomes O. At time (a-2), the head is in the middle of the magnetic pole.

In some cases, the area of the region where the magnetization is oriented in the Hi force direction (shown in a grid pattern) is larger than the region where the magnetization is oriented in the Hs force direction (hatched area). In such a case, the region where the magnetization is aligned in the HS direction is unstable and is absorbed by the region where the magnetization is aligned in the Hi force direction, and the direction of magnetization of the head pole is detected and output by rotating the deflection plane of the polarized beam. In this method, the output signal is incorrect. Furthermore, when viewed microscopically, the magnetic anisotropy within the head pole is usually not completely uniform in size and direction but is dispersed. (a-3) If the axis of easy magnetization is not perpendicular to the recording medium but tilted as shown in the figure, the magnetization in the head pole will have a uniaxial anisotropic direction when the bias magnetic field (Hb) becomes 0. A situation may also occur in which the rotational torque acts in the opposite direction to the recording signal. In such a case, if the torque generated by the easy magnetization tilting from the perpendicular direction is greater than the torque caused by the signal magnetic field, the output of the head will correspond only to the bias magnetic field and will not reflect the recorded information. Become. That is, when the bias magnetic field strength is made uniform on the head pole as in the past, at the moment when no bias magnetic field is applied (Hb=O), magnetization easily rotates in the axial direction according to the -axis anisotropy energy. As a trigger for this, a signal magnetic field is applied to the tip of the head.

At this time, the magnetization of the majority of the region of the head pole that is not affected by the signal magnetic field is also placed in an unstable state, and this region also becomes sensitive to disturbances. in this way.

If the area outside the reach of the signal magnetic field undergoes magnetization reversal regardless of the signal magnetic field due to disturbance or dispersion of magnetic anisotropy, the area is overwhelmingly wider than the range of the signal magnetic field, so
At the next instant, the magnetic pole of the entire magnetic head reverses in the direction of the disturbance, resulting in a malfunction.

On the other hand, in the head according to the present invention, the bias magnetic field is given a gradient, so even if the tip of the head magnetic pole is in a state where it is sensitive to the signal magnetic field, the bias magnetic field is not applied to the tip of the head magnetic pole. Therefore, the region where the magnetization direction of the head magnetic pole is unstable can be limited to an extremely narrow region as shown by the dotted pattern in the figure (b). This region where the direction of magnetization is unstable gradually moves farther from the medium surface as Hb decreases, and the region sensitive to Hs expands. As a result, it is possible to develop a head that is less likely to malfunction even in the presence of disturbances or dispersion of magnetic anisotropy.

A specific example will be explained below. Head magnetic pole 1 in Figure 1
A 200A thick 80% Fg-20% B thin film pattern CM (CM 5 μm, height 10 μm) was prepared, and a 3 μm thick permalloy film pattern was created as the bias magnetic field yoke 8 in FIG. 1 by sputtering and subsequent photolithography. 80% F produced by sputtering method
The e-20%B thin film has an anisotropic magnetic field (Hk) of 1000 e
It has uniaxial magnetic anisotropy, and the easy axis direction is perpendicular to the recording medium. The head magnetic pole tip is 5μ from the yoke tip.
m sticking out.

The magnetic field generated from the yoke increases or decreases in proportion to the excitation current (I), and when ■≧50 μmA, a bias magnetic field of Hk or more is applied to the entire head pole as shown in FIG.

The recording medium has a track width of 50 μm and a recording bit length of 0.
An 80% Go-20% Cr alloy thin film tape on which a 2 μm signal was recorded in saturation was used. The coercive force of Go-Cr film is 100
00e, the film thickness is 0.5 μm. This tape was brought into contact with the above head and slid at a speed of 10 .mu./sec. A high frequency current of 5 MHz was applied to the excitation coil for the bias excitation field. The current value of this bias high frequency is O
The range was set to 60 mA. To detect the magnetization of the head magnetic pole, a 2 mW He-No laser beam is irradiated at an incident angle of 60°, and the biasing force of the reflected light is f7) @ L' knee 0, i,. ,□8. picture. □ 1 □ polarized light is S polarized light.

FIG. 4 shows the relationship between the bias excitation current value and the signal reproduction output. Since the reproduction output is a mixture of the output from the bias magnetic field and the output from the recording signal, the cutoff frequency M
Only the recording signal output was extracted by passing it through an H2 low-pass filter. Furthermore, the signal reproduction output is planned as 1 when the magnetization of the head magnetic pole is reversed while being saturated. I
It can be seen that when Hb = 50 mA, that is, when Hk = Hk, the reproduction output increases rapidly and reaches di-saturation. The error rate at this time was about 10-7.

On the other hand, in FIG. 1, instead of producing the yoke 8,
A Helmholtz coil was installed outside the head to apply a uniform bias magnetic field in the track direction.

In this case as well, although it was possible to reproduce the recorded information under the condition of Hb≧Hk, the error rate was 10-1 to 104, and the signal quality was poor.

(Example 2) In the head having the structure shown in Fig. 5, the head magnetic pole was set to 0.1
μm thick permalloy film pattern (width 5μm, height 20μm
m), and has a yoke shape for applying bias.

All conditions of the recording medium were the same as in Example 1. As a method of detecting the magnetization change of the head magnetic pole, an auxiliary magnetic pole 10 was provided on the back side of the recording medium. The auxiliary magnetic pole has a cross-sectional shape with a diameter of 5
M of 0 μm. -A coil is wound 500 times around a Zn ferrite cylinder. The change in magnetization of the head magnetic pole induces a voltage in the auxiliary magnetic pole, so that signals can be reproduced.

FIG. 6 shows the relationship between the bias magnetic field excitation current (I) and the reproduction output of the recording signal generated at the auxiliary magnetic pole.

The playback output increases rapidly from around I = 30 mA, and the output reaches I = 40
The permalloy head magnetic pole of this example is also formed by sputtering technology and photolithography, and is given uniaxial anisotropy of Hk=800e, but the reproduction output is saturated. The bias magnetic field is consistent with the value of Hk. The error rate when I=50 mA is on the order of 10-'. On the other hand, in this embodiment, if the bias applying yoke is not created and a Helmholtz coil is provided outside the head-medium system to apply a uniform bias magnetic field, the bias magnetic field will have a value similar to Hk. Signal output could be detected at times. However, the error rate at this time is 10-3, and the signal quality is poor.

It can be easily inferred from the above that,
Even in a so-called thin film head as shown in FIG. 7, the sensitivity of the head can be dramatically improved by applying an alternating current bias magnetic field according to the present invention. The thin film head shown in Figure 7 detects changes in magnetization by winding a coil around the head pole itself instead of using the auxiliary pole shown in Figure 5 to detect changes in magnetization, so there is no difference in principle. It is something.

(Effects of the Invention) As explained above, in the head according to the present invention, since the bias magnetic field is given a gradient, it is possible to gradually expand the area sensitive to the recording signal on the head magnetic pole from the tip. This makes it possible to increase the sensitivity of the head and reduce malfunctions. Furthermore, since the bias magnetic field becomes smaller on the recording medium, there is also the effect that there is less risk of erasing recorded information compared to the conventional uniform bias.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of a magnetic head according to the present invention that applies an unrestricted-Bailout magnetic field to the head magnetic pole, Figure 2 is the bias magnetic field distribution in the direction perpendicular to the medium surface, and Figure 3 is when the bias magnetic field is uniform. , and a conceptual diagram showing the state of magnetization reversal in the head magnetic pole when it is non-uniform. Fig. 4 is the relationship between the bias magnetic field excitation current and the reproduction output. Fig. 5 is a non-uniform magnetic field bias magnetic head using the auxiliary magnetic pole reproduction method. FIG. 6 is a schematic diagram of the relationship between bias current value and reproduction output, FIG. 7 is a schematic diagram of a ring type thin film head to which a nonuniform bias magnetic field is applied according to the present invention, and FIG. 8 is an already known head. FIG. 2 is a principle diagram of a magnetic head having a structure in which a parallel bias magnetic field is applied to a head magnetic pole. 1... Head magnetic pole, 2... Bias magnetic field, 3...
Magnetization, 4... Magnetic recording medium, 5... Direction of easy magnetization of the head. 6... Incident polarized light, 7... Reflected polarized light, 8... Yoke for applying bias magnetic field. 9... Bias magnetic field excitation coil, 10... Auxiliary magnetic pole, 11... Spiral coil,

Claims (1)

[Claims] (1) A head core made of a magnetic material having uniaxial magnetic anisotropy is faced to a magnetic recording medium, and an alternating magnetic field is applied to the head core from the outside in a direction substantially orthogonal to the magnetic field generated from the magnetic recording medium, so that the magnetic field inside the head core is A bias application type magnetic head for detecting rotation corresponding to recording of a magnetic recording medium, characterized in that the amplitude of the alternating magnetic field has a distribution that becomes stronger as the distance from the magnetic recording medium increases.