JPH05205257A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improved durability and enhance track density in a magnetic recording medium which performs magnetic recording onto a plurality of recording tracks which are formed on a continuous magnetic layer on a non-magnetic substrate. CONSTITUTION:A recording track is formed by changing magnetic characteristics at a desired part of a continuous magnetic layer locally so that a saturated magnetization Ms of the magnetic layer of a recording track 5 is larger than the saturated magnetization Ms of the magnetic layer in a region 4 between tracks which are sandwiched by the recording tracks 5 and so that a coercive force Hc of the magnetic layer of the recording track 5 is smaller than the coercive force Hc of the magnetic layer of the region 5 between tracks. For example, ion is implanted or laser is applied externally to changing magnetic characteristics locally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a hard disk, and more particularly to a magnetic recording medium suitable for recording and reproducing a signal with a high track density.

[0002]

2. Description of the Related Art In recent years, magnetic recording devices such as hard disk devices have been widely used as large-capacity external storage devices that can be randomly accessed in the computer field.
Further, with the expansion of use, there is an increasing demand for a large recording capacity and a high recording density. Therefore, in order to meet such demands, research and development have been conducted from various fields.

Generally, as a hard disk device, a plurality of magnetic disks each having a magnetic layer provided on a non-magnetic substrate are stacked and mounted on a single rotating shaft, and a recording / reproducing head is mounted on an arm and each disk is mounted. It is known that the arm is arranged on a surface and the arm is moved by an actuator to position the head.
When information is recorded / reproduced by the hard disk device having such a structure, the head does not directly contact the disk surface rotating at high speed, but is configured to access a desired position on the disk surface in a slightly floating state. It is arranged.
Then, a signal is recorded or reproduced by the head with respect to concentric tracks on the disk surface.

In order to meet the demand for larger recording capacity in the above-mentioned hard disk device, the recording density is improved by increasing the linear recording density of the disk, that is, the density in the track direction, or the track density is increased. Attempts have been made to increase the recording density by increasing the recording density.

In order to increase the linear recording density, the spacing between head media is made as small as possible so that the magnetic field from the head does not spread and the separation loss is reduced.
Measures such as increasing the coercive force Hc of the medium to sharpen the magnetization transition of the medium have been taken. Therefore, in the small hard disk drive, the spacing between the head media is narrowed by the time the head flying height falls below 0.15 μm, and the coercive force Hc of the media is also increased up to about 1,400 Oe. And now, by these measures, the recording density is improved to a considerable extent.

On the other hand, in order to increase the track density, it is necessary to narrow the track width of the head. Therefore, in order to improve the recording density by increasing the track density, the development focus is to improve the reproducing sensitivity of the head so that a sufficient reproducing output can be maintained even if the head has a narrow track width. I've been burned.

However, even if a head having a sufficiently good reproduction sensitivity is obtained, it is difficult to avoid the phenomenon that the recording track is widened by the leakage magnetic field from the track end of the head when performing magnetic recording. It was This phenomenon has been an obstacle in increasing the track density. In order to prevent such a phenomenon, the track end surface of the head core has been processed so as to be parallel to the track length direction, or the upper and lower head cores have the same width to minimize the positional deviation. The solution was taken.

As described above, conventionally, research for improving the track density has been conducted mainly by improving the head. However, in recent years, magnetic recording media suitable for recording with high track density have been actively developed. For example, in 1989, IBM proposed a discrete track system in which a magnetic layer was formed only in the track area of the medium surface (IE
EE Transactions OnMagnetics, Vol.25, No.5, pp 3
381-3383,1989). According to this method, since the magnetic layer is not formed in the area other than the track area on the disk, the recording track width is kept constant regardless of the magnitude of the leakage magnetic field from the magnetic head. Further, it becomes possible to narrow the track interval to the very limit determined by the head position control accuracy and the crosstalk amount between adjacent tracks. Therefore, it is possible to increase the track density without being significantly affected by the processing accuracy for narrowing the track width of the head.

[0009]

However, in the magnetic recording medium of the discrete track system, there is a step difference of 0.02 to 0.05 μm between the track area and the non-track area on the surface of the medium due to the presence or absence of the magnetic layer. Therefore, there is a problem that interference between head media is likely to occur during head seek. Especially, when the flying height of the head is as small as 0.1 μm or less, the unevenness of the medium surface as high as 0.02 to 0.05 μm causes a problem that the seek durability is significantly lowered. In addition, since the magnetic material is discontinuous in a width of about several μm, the mechanical strength at the edge of the film is lower than that of the continuous film, which is also a problem in terms of durability.

Therefore, in order to avoid the above-mentioned inconvenience caused by the unevenness of the medium surface, a method of narrowing the track width without causing unevenness on the medium surface has also been proposed. For example, a method of forming tracks and separating the tracks from each other by filling a groove formed on a substrate with a magnetic material (Japanese Patent Laid-Open No. 2-189715: Magnetic disk and its manufacturing method and recording device, Japanese Patent Laid-Open No. 2-189715). 201
730: magnetic recording medium). Unlike the above-mentioned methods, these methods have no unevenness on the surface of the medium, and thus have no adverse effect on seek durability and the like. However, since the magnetic substance is deposited in the groove formed on the substrate made of a different material and the magnetic substance is interrupted by the track width, the adhesive force between the magnetic substance and the material forming the groove is still small. .. Therefore, film peeling is likely to occur due to contact with the head, and the problem in terms of durability has not been solved.

Therefore, the present invention has been made to solve such conventional problems, and provides a magnetic recording medium having a structure in which the track width is narrowed in order to increase the track density and which is excellent in durability. The purpose is to provide.

[0012]

The magnetic recording medium of the present invention is a magnetic recording medium for performing magnetic recording on a plurality of recording tracks formed on a continuous magnetic layer on a non-magnetic substrate. The saturation magnetization Ms is larger than the saturation magnetization Ms of the magnetic layer in the inter-track region sandwiched between the recording track and the recording track, and the coercive force Hc of the magnetic layer in the recording track is the magnetic property of the inter-track region. It is characterized in that the recording track is formed by locally changing the magnetic characteristics of a desired portion of the continuous magnetic layer so as to be smaller than the coercive force Hc of the layer.

In manufacturing the magnetic recording medium of the present invention configured as described above, a magnetic layer which is a continuous film is formed on a non-magnetic substrate by a conventional method such as a sputtering method or a vapor deposition method, and then a track is formed. Ions such as nitrogen ions and oxygen ions are implanted as impurities into the inter-regions from the outside by an ion implantation method or the like. Alternatively, after forming the magnetic layer as a continuous film,
The magnetic layer may be heat-treated by irradiating the portion to be the inter-track region with a laser.

[0014]

In the magnetic recording medium of the present invention, by providing a magnetic layer having different magnetic characteristics between the recording tracks, the recording tracks on the surface of the medium and the state of residual recording magnetization of the portions other than the recording tracks. Are configured to be significantly different. As a result, the recording signal can be correctly recorded only on the recording track portion, and the recording residual magnetization of the portion other than the recording track can be extremely reduced.

Saturation magnetization Ms of the magnetic layer in the recording track portion
Is larger than the saturation magnetization Ms of the magnetic layer in the track-to-track region sandwiched between the recording tracks. As a result, when signals are recorded in the recording track and the inter-track area with the same recording magnetic field, a sufficient recording magnetization remains in the recording track, while the saturation magnetization itself is small in the inter-track area. In addition, only a small recording magnetization remains. Therefore, it is possible to record a signal with a predetermined track width regardless of the magnitude of the leakage magnetic field from the magnetic head or even when the signal recording conditions are different.

Further, by making the coercive force Hc of the magnetic layer in the recording track portion smaller than the Hc of the magnetic layer in the inter-track region sandwiched between the recording tracks, the magnetic material in the portion other than the recording track is formed. Can be made hard to be magnetized. Therefore, it is possible to record a signal with a predetermined track width regardless of the magnitude of the leakage magnetic field from the magnetic head or even when the signal recording conditions are different.

That is, between the recording track and the track-to-track region, the magnetic characteristics of the magnetic layer and the saturation magnetization M are as described above.
By differentiating s from the coercive force Hc, the same effect can be obtained without cutting the magnetic layer, that is, when the recording tracks are separated with a predetermined width while maintaining the continuous film state. can get.

In order to make the magnetic characteristics of the recording track and the inter-track region different, a magnetic layer which is a continuous film is formed on a non-magnetic substrate according to a conventional method, and then a portion to be the inter-track region is formed. Ions are implanted from the outside. The ions injected into the magnetic material bond with atoms inside the magnetic material or enter between the magnetic material atoms, and change the magnetic characteristics of that portion. Alternatively, as another method, after the magnetic layer is formed as a continuous film, the portion to be the inter-track region is irradiated with a laser to heat-treat the magnetic layer. The laser irradiation changes the crystal structure of the magnetic material,
The magnetic properties such as coercive force are changed.

When the magnetic characteristics of the recording track and the inter-track area are made different by the above method,
The track interval can be narrowed to the very limit determined by the head position control accuracy and the crosstalk amount between adjacent tracks. Therefore, it is possible to increase the track density without being significantly affected by the processing accuracy for narrowing the track width of the head.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1 is a schematic view showing a part of the cross-sectional structure of a magnetic recording medium of one example of the present invention, showing a vertical section in a direction perpendicular to the length direction of a recording track. As shown in FIG. 1, a non-magnetic underlayer 2 made of Cr and having a thickness of 0.1 μm is formed on a glass substrate 1 having a diameter of 2.5 inches and a thickness of about 0.64 mm by a bias sputtering method in an argon gas atmosphere. Formed by. And on top of that, the thickness of CoCrTa is 0.03μ.
The m 3 magnetic layer 3 was formed by a DC magnetron sputtering method in an argon gas atmosphere with a small residual gas such as oxygen. After forming the magnetic layer 3, nitrogen ions as impurities were introduced into the inter-track region 4 from above the magnetic layer 3 by an ion implantation method at a vacuum degree of 10 ⁻⁴ Pa or less. At this time, the invading nitrogen ions are bonded to Co, Cr, etc. in the magnetic material in the inter-track region 4, particularly in the surface layer portion, and have a smaller saturation magnetization than the magnetic material in the recording track portion 5 which is not subjected to ion implantation. Become. After the ion implantation process, a 0.01 μm thick protective film 6 made of silicon oxide was formed on the magnetic layer 3.

Table 1 shows an inter-track region 4 into which nitrogen ions are implanted and a recording track portion 5 which is not implanted with nitrogen ions.
The following is a comparison of the saturation magnetization Ms and the coercive force Hc.

[0023]

[Table 1] As is clear from Table 1, CoCr was formed by nitrogen ion implantation.
The saturation magnetization Ms of the Ta magnetic body 3 decreases, and at the same time, the coercive force Hc
Has risen.

Embodiment 2 FIG. 2 is a schematic view showing a part of the cross-sectional structure of a magnetic recording medium of Embodiment 2 of the present invention, and shows a vertical cross section in a direction perpendicular to the length direction of a recording track as in FIG. ing. As shown in FIG. 2, a soft magnetic underlayer 8 made of FeN having a thickness of 0.2 μm was formed on a ceramic substrate 7 having a diameter of 2.5 inches and a thickness of 0.4 mm in an argon gas atmosphere containing 10% nitrogen. At RF
It was formed by the sputtering method. And on top of that, Co
The magnetic layer 9 made of Pt and having a thickness of 0.02 μm is set in an argon gas pressure.
It was formed by DC magnetron sputtering at 0.8 Pa.
Further thereon, a protective film 10 made of silicon nitride and having a thickness of 0.005 μm was formed. After the protective film 10 was formed, a laser was applied to the inter-track region 4 of the medium with a spot diameter of 1.0 μm to locally raise the temperature to several hundreds of degrees. By the laser irradiation, the crystal structure of the CoPt magnetic substance 9 was changed, the saturation magnetization Ms of the laser irradiation was lowered, and the coercive force Hc was increased.
Table 1 also shows changes in saturation magnetization Ms and coercive force Hc before and after laser irradiation.

Comparative Example In order to know the effect of the present invention, as a comparative example, a magnetic recording medium was manufactured in the same manner as in Example 1 except that the process of changing the magnetic characteristics of the inter-track region was not performed.

Then, the off-track characteristics of the magnetic recording media of Examples 1, 2 and Comparative Examples obtained as described above were evaluated. The off-track characteristics were evaluated by recording a signal on a medium formed into a 2.5-inch hard disk using a thin-film magnetic head, and then measuring the reproduction output while shifting the head position in the track width direction. FIG. 3 shows the measurement results of the media of Example 1 and the comparative example.

As is apparent from FIG. 3, in Example 1 in which the magnetic characteristics of the inter-track region were changed, compared with the untreated Comparative Example, the reproduction output was started when the off-track amount / track width value exceeded ± 0.5. Indicates that the track is sharply cut and sharply cut. Therefore, Example 1
Can be used in a higher track density state. When the off-track characteristics of the medium of Example 2 were measured in the same manner as in Example 1, the same measurement results as in Example 1 were obtained.

Further, with respect to the media of Examples 1, 2 and Comparative Example, the durability in the seek state of the head was examined. As a result, in the medium of Comparative Example, peeling of the magnetic film occurred after 200,000 seeks, whereas in the media of Examples 1 and 2, peeling of the magnetic film did not occur even after 5 million seeks. Showed excellent durability.

[0029]

As described above, according to the present invention, even when the leakage magnetic field from the track end of the magnetic head is large, the magnetic characteristics between the tracks on the medium are changed to change the track. It is possible to record a signal at a fixed width determined by the width and at a position without positional deviation. Therefore, the track pitch can be narrowed, and the track density can be increased. Further, since the magnetic material is a continuous film, a magnetic recording medium having good durability can be obtained even when the head is in a seek state.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic recording medium of Example 1 of the present invention.

FIG. 2 is a sectional view of a magnetic recording medium of Example 2 of the present invention.

FIG. 3 is a diagram showing off-track characteristics of Example 1 of the present invention and a comparative example.

[Explanation of reference symbols] 1 ... Glass substrate 2 ... Non-magnetic Cr underlayer 3 ... CoCrTa magnetic layer 4 ... Track area 5 ... Recording track portion 6 ... Silicon oxide protective film 7 ………… Ceramics substrate 8 ………… FeN soft magnetic underlayer 9 ………… CoPt perpendicular magnetic layer 10 …… Silicon nitride protective film

Claims (1)

[Claims] 1. A magnetic recording medium for performing magnetic recording on a plurality of recording tracks formed on a continuous magnetic layer on a non-magnetic substrate, wherein the saturation magnetization Ms of the magnetic layer of the recording tracks is:
Greater than the saturation magnetization Ms of the magnetic layer in the inter-track region sandwiched between the recording tracks and the recording tracks, and
The coercive force Hc of the magnetic layer of the recording track is smaller than the coercive force Hc of the magnetic layer of the inter-track region.
A magnetic recording medium, wherein the recording track is formed by locally changing the magnetic characteristics of a desired portion of the continuous magnetic layer.