JPH04370501A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To increase reproduced output by allowing erasing magnetic field intensity He on a surface to satisfy a specified condition for the magnetic recording medium whose coercive force squareness ratio S* is over 0.8. CONSTITUTION:Above mentioned purpose is attained by making magnetic field intensity on the surface of the magnetic recording medium at a position a bit length portion distant from the center of a magnetic gap of a magnetic head to a training side He=28500(S*)<3>-70070(S*)<2>+57350(S*)-15060Oe for the magnetic recording medium whose coercive force squareness ratio S* is over 0.8.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device used in an external storage device for a computer or the like, and particularly to a combination of a magnetic head and a recording medium suitable for high-density magnetic recording.

0002

2. Description of the Related Art In recent years, there has been an increasing demand for higher densities in magnetic disk drives, and efforts are being made to develop and improve the performance of thin film media having high coercive force and thin film magnetic heads capable of writing to high coercive force media. Co-based magnetic materials such as CoCrNi and CoCrTa have high coercive force and have been put into practical use as thin film media. In particular, CoCrTa described in JP-A-1-133217 is known to have a coercive force squareness ratio S* of 0.8 to 0.9, a high coercive force of 1000 to 1500 Oe, and low noise. On the other hand, a thin film magnetic head consists of a magnetic core made of a magnetic thin film having a yoke structure and a conductive layer coil sandwiched between the magnetic core, and a magnetic pole portion at the tip of the core runs against the medium to perform recording and reproduction. In order to improve the recording and reproducing efficiency of the head and prevent magnetic saturation, it is desirable that the rear core has as wide a cross-sectional area as possible, and in order to perform high-density recording and reproducing, it is preferable that the cross-sectional area of the tip of the magnetic pole be as narrow as possible. Regarding the planar shape, see JP-A-55-
As described in No. 84019, the magnetic film of the rear core is designed to gradually expand with respect to the rectangular magnetic pole tip having a width approximately equal to the track width facing the medium.

0003

[Problems to be Solved by the Invention] This conventional technology has a problem in that when the recording capacity is increased by increasing the magnetomotive force of the head in order to sufficiently record on a high coercive force medium, the output decreases (Figure 2). . This phenomenon is known as the recording demagnetization phenomenon, and until now it has been known that media with a coercive force of 1000 Oe or less,
In combination with a thin-film magnetic head having sufficient recording ability to write on this medium, almost no recording demagnetization occurred. Recording demagnetization is caused by the broadening of the magnetic field distribution of the head when the magnetomotive force is increased, and it is thought that the problem will become more serious in the future as density increases and the coercive force of the medium increases. Recording demagnetization is also caused by poor S* of the medium.
The amount of demagnetization varies depending on the balance between the magnetic field distribution of the head and the S* of the medium. An object of the present invention is to improve a magnetic disk drive so that recording demagnetization is less likely to occur by controlling the magnetic field distribution of a magnetic head to an optimal value for S* of a magnetic recording medium.

0004

[Means for Solving the Problem] The above object is to provide a magnetic recording medium with a coercive force squareness ratio S* of 0.8 or more at a position separated by a bit length from the center of the magnetic gap of the magnetic head to the trailing side. The magnetic field strength on the surface of the magnetic recording medium is He≦28500(S*)3-70070(S*
)2+57350(S*)-15060Oe.

[0005]

[Operation] FIG. 3 shows the head magnetic field distribution in the medium running direction when the spacing is 0.2 μm, and the value at the center of the magnetic head. FIG. 4 shows the magnetization process of the medium due to this head magnetic field distribution. As shown in the figure, the magnetic field strength He at a position a bit length t away from the center of the magnetic gap of the magnetic head toward the trailing side corresponds to the erase magnetic field of the medium. When this erase magnetic field is large, the residual magnetization Mr of the medium decreases, and recording demagnetization corresponding to ΔM in FIG. 4 occurs. When He is controlled so as to satisfy the above relationship with respect to the coercive force squareness ratio S* of the medium, the decrease in Mr is suppressed and recording demagnetization is reduced.

[0006]

EXAMPLES Examples of the present invention will be described below. FIG. 5 is a plan view of a thin film magnetic head used in an embodiment of the present invention. 10 is a magnetic core formed by patterning a magnetic film of permalloy, amorphous or the like formed on a substrate by sputtering or the like using ion milling or the like using a photoresist as a mask, and 20 is a conductor coil. The upper magnetic layer and the lower magnetic layer of the magnetic core are in contact at 11 to form a yoke structure, and a conductor coil 20 provided between the upper and lower magnetic layers is completely insulated by a resin insulating layer. In this example, permalloy was used for the magnetic film. In addition, by changing the film thickness of the upper magnetic core from 1 to 3 μm, the magnetic field distribution can be improved.
In particular, various heads with different erase magnetic fields He were manufactured. The magnetic field distribution was measured using a magnetic field observation SEM (Intermag '90, Digest FP-05) developed by Shinada et al. that measures the bending of a scanning electron beam due to the magnetic field and processes the data. On the other hand, as a thin film medium, a film with a thickness of 50 nm was formed on a NiP substrate using a magnetron sputtering device.
A Cr base film of 60 nm is formed on top of this.
a A magnetic film was formed to produce a disk. Several types of media with different S* were produced by changing the sputtering conditions. Magnetic properties such as squareness ratio S* were determined from magnetization curves measured using VSM. The coercive force of all media is 1200O
It was controlled to be equal to or higher than e.

For example, FIG. 6 shows the results of investigating the magnetomotive force dependence of reproduction output using a combination of a thin film medium with an S* of 0.82 and various heads with different erasing magnetic fields He. The recording was performed at a spacing of 0.2 μm, a circumferential speed of 12.7 m/s, and a frequency of 9.
The frequency was 0.09MHz. At this time, the recording density is approximately 100M
b/m2. Also, the bit length is 0.7 μm, so it is 0.7 μm from the center of the magnetic gap of the magnetic head to the trailing side, and 0.2 μm from the medium facing surface of the head.
The erasing magnetic field He at a distant position was measured using a magnetic field SEM and is shown in the figure. In addition, when we measured the magnetic field strength at the gap center coordinates of the head at a position 0.2 μm away from the medium facing surface of the head, all values were 4000 to 6.
It was 000 Oe. As you can see from the figure, S* is 0.8
For the recording medium No. 2, when He is 260 Oe or less, almost no recording demagnetization occurs and the demagnetization rate is 0.1% or less, so the present invention is highly effective. Moreover, when He was 560 Oe or less, the demagnetization rate was 5% or less.

Similar experiments were conducted on a number of other media having different coercive force squareness ratios S*. As another embodiment of the present invention, for example, for a medium with S* of 0.95, He
If it is below 620 Oe, the demagnetization rate will be below 5%, and H
When e was set to 320 Oe or less, there was almost no demagnetization. Similar experiments were carried out on various S* media, and the critical magnetic field of the erasing magnetic field He at which demagnetization does not occur is determined. The results are shown in FIG. He=28500(S*)3-70070(S*)2+
Under the conditions below the dotted line, which can be approximated by 57350 (S*) - 15060, the demagnetization rate is 5% or less and He = 28500 (S
*)3-70070(S*)2+57350(S*)-
Under conditions below the solid line approximated by 15360, almost no recording demagnetization occurred and the demagnetization rate could be suppressed to 0.1% or less. In fact, as a result of measuring recording demagnetization using values throughout the area that satisfy these conditions, the demagnetization was 0.1
% or less, or 5% or less. By controlling the relationship between the coercive force squareness ratio S* of the medium and the erase magnetic field He of the magnetic head in this manner, recording demagnetization can be reduced. In the future, as recording densities advance and the coercive force of the medium increases further, the effects of the present invention will become more significant.

[0009]

According to the present invention, since the recording demagnetization phenomenon in a magnetic disk device can be reduced, the reproduction output can be increased and the performance of the device can be improved.

[Brief explanation of drawings]

[Figure 1] Coercive force squareness ratio S* of the medium that does not cause recording demagnetization
The relationship between the erasing magnetic field He of the head and the erasing magnetic field He is shown.

FIG. 2 shows a recording demagnetization phenomenon, which is a phenomenon in which the reproduction output decreases as the magnetomotive force increases.

FIG. 3 shows the medium traveling method component of the head magnetic field distribution at a spacing of 0.2 μm.

FIG. 4 shows the magnetization process of the medium due to the head magnetic field.

FIG. 5 shows a plan view of a thin film magnetic head used in an example of the present invention.

[Figure 6] For a medium with a coercive force squareness ratio S* of 0.82,
The results of measuring recording demagnetization using various heads with different erase magnetic fields are shown.

[Explanation of symbols]

S*... Coercive force squareness ratio of medium, He... Erase magnetic field of magnetic head, Mr... residual magnetization, ΔMr... amount of demagnetization, 10... magnetic core magnetic film, 20... conductor coil, 11... upper and lower magnetic film contact portion.

Claims (5)

[Claims] Claims: 1. A magnetic recording medium with a coercive force squareness ratio S* of 0.8 or more, and a magnetic field strength on the surface of the magnetic recording medium at a position separated by a bit length from the center of the magnetic gap to the trailing side of the magnetic head. He≦28500(S*)3-70
070(S*)2+57350(S*)-15060O
e, preferably He≦28500(S*)3-7007
1. A magnetic disk device comprising a combination of thin film magnetic heads of 0(S*)2+57350(S*)-15360 Oe. 2. The magnetic disk device according to claim 1, wherein the magnetic field strength on the surface of the magnetic recording medium at the center coordinates of the magnetic gap of the magnetic head is at least twice the coercive force of the medium. . 3. The magnetic disk device according to claim 1, wherein the magnetic field strength on the surface of the magnetic recording medium at the center coordinates of the magnetic gap of the magnetic head is 4000 Oe or more. 4. The magnetic disk device according to claim 1, wherein the spacing between the head media is 0.2 μm or less. 5. The magnetic disk device according to claim 1, wherein the magnetic disk device has a recording density of 100 Mb/m 2 or more.