JPH07129953A - Magnetic recording disk and magnetic recording method thereof - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To improve the direct current magnetization reproduction signal output in a magnetic layer etching type perpendicular magnetic recording disk, and to perform high speed direct current magnetic recording on the uneven signal portion of the magnetic recording disk. To do. In a so-called perpendicular magnetic recording medium having at least a perpendicular magnetic recording layer and a soft magnetic backing layer on a non-magnetic substrate, at least a part of a data track or a servo signal portion is magnetically unevenly formed. In addition, the magnetic recording disk is characterized in that only the perpendicular magnetic recording layer portion is removed in the concave portion. A magnetic recording method is characterized in that a DC magnetic field is collectively applied in the vertical direction of one or a plurality of the magnetic recording disks.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a non-magnetic substrate having at least a perpendicular magnetic recording layer such as CoCr having magnetic anisotropy in the vertical direction of the substrate and a soft magnetic backing layer such as permalloy. A magnetic layer etching type perpendicular magnetic recording disk in which at least a part of a data track or a servo signal portion of a so-called perpendicular magnetic recording medium is magnetically separated and formed by a lithographic method or the like to obtain a high DC magnetization reproduction signal. And a magnetic recording method capable of performing high-speed DC magnetization recording on the magnetic recording disk.

[0002]

2. Description of the Related Art In a magnetic recording disk such as a hard disk used for an external storage device for a computer, etc., the amount of stored information has increased in recent years, and therefore, it has been required to further increase the density of a signal recorded per unit area. It has come to be done. In order to improve such an areal recording density, it is necessary to improve both or either of the linear recording density and the track recording density.

In order to improve the linear recording density and the track recording density, it goes without saying that the reproduction output per unit track width and unit medium residual magnetization / film thickness product of the magnetic head is improved. Is to reduce the reproduction waveform width and medium noise, but to improve the track density,
It is considered that the reduction of fringing noise at the time of recording or reproduction and the improvement of tracking accuracy are the main problems, respectively.

As one of effective methods for dramatically improving the linear recording density, in recent years, a recording medium, which has magnetic anisotropy on a non-magnetic substrate and has a magnetic anisotropy at least in the vertical direction of the substrate, has been used.
A so-called perpendicular magnetic recording medium having a perpendicular magnetic recording layer such as oCr and a soft magnetic backing layer such as permalloy is used, and a single magnetic pole head is used as a recording / reproducing head.
A so-called perpendicular magnetic recording system has been proposed.

On the other hand, as an effective method for improving the track density on the recording medium side, by using a so-called discrete track type medium in which recording tracks are magnetically separated, fringing noise during recording or reproduction is used. There are known methods for avoiding the occurrence of. According to this method, it is possible to obtain a high-precision servo signal output without using an expensive servo writer by forming the servo signal portion separately at the same time and subjecting this portion to direct-current magnetization.

As a method for manufacturing such a discrete track type medium, a method of separately forming a signal recording portion by etching or demagnetizing a part of a magnetic layer formed on a flat substrate, and an injection molding method. A method is generally known in which a signal recording portion is preliminarily formed in a concavo-convex pattern by a method such as the above, and then a magnetic layer or the like is formed on the substrate.

As a magnetic recording layer for a discrete track type medium, CoCrTa or Co is formed on an underlayer such as Cr.
It is usual to use a so-called in-plane magnetic recording medium formed with CrNi, CoCrPt, etc.
As disclosed in No. 621, an example using a so-called perpendicular magnetic recording medium having a perpendicular magnetic recording layer such as CoCr having magnetic anisotropy in the vertical direction of the substrate and a soft magnetic backing layer such as permalloy is also used. is there.

However, in such a discrete track type perpendicular magnetic recording medium, when a part of the magnetic layer is etched by, for example, a general lithography technique, as disclosed in JP-A-04-310621, etc. In the concave portion on the magnetic disk, "the magnetic layer does not exist" is usually present as shown in FIG. This is described in USP 3,258,750 and JP-A-49-1023.
The same applies when an in-plane magnetized film is used for the magnetic recording layer, as disclosed in No. 03, etc.

There is no particular description of the method of direct-current magnetizing the uneven signal portion when the magnetic recording layer is a perpendicular magnetic recording medium, but when the magnetic recording layer is an in-plane magnetic recording medium. In general, a method of direct-current magnetizing the convex magnetic layer using a magnetic head is used.

[0010]

A so-called perpendicular magnetic recording layer having a perpendicular magnetic recording layer of CoCr or the like having a magnetic anisotropy at least in the substrate vertical direction and a soft magnetic backing layer of Permalloy or the like on a non-magnetic substrate. In a magnetic recording medium, a magnetic layer etching type perpendicular magnetic recording disk in which at least a part of a data track or a servo signal part is separately formed by etching a part of a magnetic layer, for example, as described above, However, in the case where the servo signal is formed unevenly so that the magnetic layer does not exist and the signal portion is DC magnetized, there is a problem that the DC magnetization reproduction output is very low.

The recess of the conventional magnetic layer etching type perpendicular magnetic recording disk as described in Japanese Patent Laid-Open No. 04-310621 is supposed to be used as a guard band provided between tracks, and thus, such a structure is used. It is considered that no problem has occurred, but when a servo signal is obtained by direct-current magnetizing the convex portion in the circumferential direction of the magnetic recording disk, such a problem occurs.

Further, in the case where the uneven signal portion of the magnetic layer etching type perpendicular magnetic recording disk is DC magnetized by using the magnetic head, after the disk is chucked by the spindle or the drive, the magnetic head is placed over the entire recording area. It is necessary to DC-magnetize the concavo-convex signal portion by flying, and for example, considering the productivity of the disk when recording a servo signal using this method,
This is better than the recording method using a normal servo writer, but there is a problem that it is still insufficient.

[0013]

According to the present invention, Co having a magnetic anisotropy is provided on a non-magnetic substrate at least in the vertical direction of the substrate.
In a so-called perpendicular magnetic recording medium having a perpendicular magnetic recording layer such as Cr and a soft magnetic backing layer such as permalloy, at least a part of a data track or a servo signal portion is magnetically separated by unevenness by a lithography method or the like. The magnetic recording disk is characterized in that only the perpendicular magnetic recording layer portion is removed in the recess.

Further, according to the present invention, in the above magnetic recording disk, by applying a DC magnetic field to one or a plurality of disks simultaneously in the disk vertical direction, the perpendicular magnetic field of each magnetic recording disk is increased. A magnetic recording method is characterized in that the recording layer is collectively DC magnetized.

[0015]

The magnetic recording disk according to the present invention can obtain a high DC magnetic reproduction signal output, especially in a magnetic layer etching type perpendicular magnetic recording disk for high recording density, and the magnetic recording method according to the present invention is It enables high-speed DC magnetization recording on recording disks.

[0016]

EXAMPLES The present invention will be described below based on specific examples, but it goes without saying that the present invention is not limited to these examples.

In all of the present Examples and Comparative Examples, first, an in-line static opposed DC magnetron sputtering apparatus was used on a crystallized glass substrate for a hard disk having an outer diameter of 65 mm, an inner diameter of 20 mm and a plate thickness of 0.89 mm. ,
Substrate heat treatment is performed to make the backing layer 1 μm and the magnetic layer 0.
A magnetic recording disk for perpendicular magnetic recording was produced by forming 1 μm.

A Nb-based permalloy NiFeNb alloy was used for the backing layer and a CoCr alloy was used for the magnetic layer as the target, and a film was formed using Ar gas. However, all film forming conditions were such that the background pressure in the chamber before introducing Ar gas was 2 × 10 ⁻⁶ Pa and the Ar gas pressure during sputtering was 0.
The applied power density was 2 Pa and the input power density was 30 kW / m ² .

By changing the CoCr target composition of the perpendicular magnetic recording layer, three types of magnetic recording disks 1, 2 and 3 having different magnetic characteristics of the perpendicular magnetic recording layer were produced. Table 1 shows that only the perpendicular magnetic recording layer of these magnetic recording disks was directly sputtered on the crystallized glass substrate to measure the coercive force in the perpendicular direction of the film and the saturation magnetization measured by using a sample vibrating magnetometer (VSM). Indicates the amount.

[0020]

[Table 1] Below, first, regarding the magnetic recording disk according to the present invention,
A description will be given based on a specific example.

Example 1 Part of the perpendicular magnetic recording layer of the magnetic recording disk 1 was etched by a general lithographic method.

That is, after coating the entire surface of the magnetic recording disk with photoresist, as shown in FIG. 1, the convex portion length is 5 μm in a radial direction from the center of the substrate in the circumferential direction of the substrate.
The resist was patterned by exposure so that a uniform pattern having a recess length of 5 μm was formed on a part of the magnetic recording disk.

Next, using the resist as a mask, the protective film layer and the perpendicular magnetic recording layer alone are removed by anisotropic etching by the ion milling method with respect to the groove portion in FIG. 1, followed by oxygen plasma treatment and acetone cleaning. The magnetic layer etching type perpendicular magnetic recording disk was manufactured by removing the resist.

However, the concavo-convex pattern shown in FIG. 1 used in the present embodiment is not intended for an actual hard disk drive system, and tracking is not particularly required when measuring the reproduction output of the concavo-convex portion. In particular, it is manufactured for an experiment so that the projections can be continuously formed radially in the disk radial direction so that the reproduction output can be measured over the entire track width of the reproducing head.

Therefore, if a good reproduction output is obtained in such an experimental pattern, it is clear that a good reproduction output can be obtained even if the concavo-convex pattern is formed as a servo signal or the like. FIG. 2 shows a conceptual diagram of a cross section in the circumferential direction of the magnetic recording disk according to this embodiment.

Comparative Example 1 In the same manner as in Example 1, the protective film layer, the perpendicular magnetic recording layer and the soft magnetic backing layer of the magnetic recording disk 1 were removed in the groove portion in FIG. The conceptual diagram of the cross section in the circumferential direction of the magnetic recording disk according to this comparative example is the same as FIG.

After each of the magnetic disks of Example 1 and Comparative Example 1 was chucked on a spin stand, a single pole head having a track width of 10 μm, a main pole length of 0.3 μm and a number of turns of 30 was processed into a microslider. At a relative speed of 6 m / sec (head flying height of 0.06 μm), a large recording current of about 40 mA was applied to the magnetic head to direct-current magnetize all the convex portions of the magnetic layer on the magnetic disk in the direction perpendicular to the film. After recording the magnetization, the reproduction output was measured.

Table 2 shows the reproduction outputs of the DC magnetizing signals of Example 1 and Comparative Example 1 when the reproduction output of Comparative Example 1 was set to 0 dB.
Shown in.

[Table 2]

As is clear from the results of Table 2, C having a magnetic anisotropy on at least the substrate vertical direction on the non-magnetic substrate.
At least a part of a data track or a servo signal portion of a so-called perpendicular magnetic recording medium having a perpendicular magnetic recording layer such as oCr and a soft magnetic backing layer such as permalloy is magnetically formed by a lithographic method or the like by magnetic separation. In the magnetic layer etching type perpendicular magnetic recording disk thus obtained, by removing only the perpendicular magnetic recording layer portion in the concave portion, compared with the conventional magnetic layer etching type perpendicular magnetic recording disk having no magnetic layer in the concave portion. ,
It is possible to obtain a very high DC magnetization reproduction output.

As described above, the reason why the DC magnetization reproduction output of the magnetic recording disk of Example 1 according to the present invention is significantly higher than that of the magnetic recording disk of Comparative Example 1 is as follows.
In the magnetic recording disk of Comparative Example 1, since the soft magnetic backing layer is discontinuous, it is difficult for the magnetic flux to form a closed loop between the single magnetic pole head, the perpendicular magnetic recording layer, and the soft magnetic backing layer. While it becomes difficult for the magnetic flux of the medium to flow into the main magnetic pole of the head, in the magnetic recording disk of Example 1, the soft magnetic backing layer is continuous, and therefore the magnetic layer is not normally formed with irregularities. Like the perpendicular magnetic recording medium of, the magnetic flux easily forms a closed loop between the single magnetic pole head, the perpendicular magnetic recording layer, and the soft magnetic backing layer, and the magnetic flux of the medium easily flows into the main magnetic pole of the head. To be

However, when only the perpendicular magnetic recording layer is removed by the lithography method, it is extremely difficult to remove only the perpendicular magnetic recording layer without removing the soft magnetic backing layer. In the magnetic recording disk according to the present invention, a part of the perpendicular magnetic recording layer remains in the concave portion of the magnetic layer to such an extent that the direct current magnetization reproduction output is not significantly deteriorated, or the magnetic recording disk of the soft magnetic backing layer is formed. What is also included that is partly etched,
It is clear from the context.

Next, the magnetic recording method according to the present invention for the magnetic recording disk according to the present invention will be described based on specific examples. Example 2 Two magnetic recording disks of Example 1 were prepared and a cylindrical electromagnet having a diameter of 100 mm as shown in FIG. 3 was used.
6 for two discs simultaneously in the disc vertical direction
A perpendicular magnetic recording layer of each disk was collectively DC magnetized by collectively applying a DC magnetic field of 00 kA / m to the entire surface of the disk.

However, as an alternative, the electromagnet in FIG. 3 may be replaced with a permanent magnet, and the perpendicular magnetic recording layer may be DC magnetized by disposing a magnetic disk in the solenoid. The time required for DC magnetization recording of these two disks was about 30 seconds for attaching and detaching the disks and about 2-3 seconds for applying a magnetic field, which was about 30 seconds in total.

Further, the direct current magnetization signal reproduction output of each magnetic recording disk on which direct current magnetic recording was carried out in this way was measured using a single pole head, and in both disks, reproduction of +13 dB which is equal to or higher than that of Example 1 was reproduced. Output was obtained.

Comparative Example 2 Two magnetic recording disks of Example 1 were prepared, and each disk was chucked on a spin stand in the same manner as in Example 1, and then a single magnetic pole head was used. DC magnetization recording was performed by DC magnetizing all the convex portions of the magnetic layer on the magnetic disk in the direction perpendicular to the film.

The time required for DC magnetization recording of these two discs is about 2 minutes for each disc mounting, head loading, unloading operation, and removal, and about 5 seconds for magnetic field application. Yes, it took about 4 minutes with two disks.

As is clear from the above description, in the above-mentioned magnetic recording disk according to the present invention, by applying a DC magnetic field to one disk or a plurality of disks simultaneously in the disk vertical direction at once. , Compared with a general magnetic recording method in which DC magnetic recording is performed on disks one by one using a conventional magnetic head by using a magnetic recording method in which the perpendicular magnetic recording layers of each magnetic recording disk are collectively DC magnetized. Then, it can be seen that it is possible to perform high-speed DC magnetization recording on the magnetic recording disk.

Further, in this magnetic recording method, the larger the number of disks that are subjected to DC magnetization at one time,
It is clear from the context that it is possible to perform direct current magnetic recording on a magnetic recording disk at a higher speed than in the conventional magnetic recording method.

Next, in the magnetic recording method according to the present invention as described above, the magnetic recording method according to the present invention in which the perpendicular magnetic field strength required to obtain a sufficient reproduction output from the direct current magnetization of the convex portion is defined is concretely implemented. An explanation will be given based on an example.

First, the theory underlying the present invention will be described below. In a region where the reproduction output from the convex DC magnetization is saturated with an increase in the applied magnetic field strength, the magnetization inside the perpendicular magnetic recording layer has a value close to the saturation magnetization amount Ms of the perpendicular magnetic recording layer. Therefore, the minimum value _Hmin of the required perpendicular magnetic field strength is the magnetic particle magnetic anisotropy inside the perpendicular magnetic recording layer, if the demagnetizing field coefficient inside the perpendicular magnetic recording layer is N (0 ≦ N ≦ 1). When the vertical orientation of is good, the self-demagnetizing field inside the perpendicular magnetic recording layer is taken into consideration and it is considered that it is expressed by the following equation.

H _min ≈Hc + N · Ms

Of course, since the vertical orientation of magnetic particle magnetic anisotropy inside the perpendicular magnetic recording layer varies depending on the medium in practice, the above formula is not exact, but CoCr used for perpendicular magnetic recording is used. It is considered that the above equation is approximately satisfied because the magnetic films such as the above usually have very good perpendicular orientation of magnetic particle magnetic anisotropy.

Therefore, assuming that the value of N does not vary greatly depending on the medium, the applied magnetic field strength H is (H-H
c) / Ms, and by examining the normalized magnetic field strength dependence of the reproduction output from the convex portion DC magnetization, the required DC magnetic field strength can be evaluated under the same conditions even among media having different magnetic characteristics. Things can be predicted.

Example 3 and Comparative Example 3 For each of the magnetic recording disks 2 and 3 shown in Table 1, only the protective film layer and the perpendicular magnetic recording layer were formed in FIG. 1 according to the same method as in Example 1. After removing the groove portions, the respective disks were collectively subjected to DC magnetization recording in the same manner as in Example 2, and the reproduction output of the DC magnetization signal was measured using a single magnetic pole head. At this time, the applied vertical magnetic field is 0-
It was changed between 600 kA / m.

FIG. 4 shows the normalized applied magnetic field (H-Hc) / Ms dependency of the reproduction output of the DC magnetizing signal. However, here, the reproduction output is the saturation output obtained when the applied magnetic field strength during magnetization is increased in each magnetic disk.
Standardized as 1.

As is apparent from FIG. 4, in the above-described magnetic recording method according to the present invention, the perpendicular coercive force of the perpendicular magnetic recording layer is Hc (A / m) and the saturation magnetization is Ms (A / M).
m), Hc + 0.5M in the disc vertical direction
It can be seen that by using a DC magnetic field larger than s, good DC magnetization reproduction output can be obtained even in media having different magnetic characteristics of the perpendicular magnetic recording layer.

The substrate material used in the present invention is aluminum,
Any tempered glass, crystallized glass, carbon, plastic, etc. may be used as long as they are generally used in this type of magnetic recording medium.

The soft magnetic backing layer used in the present invention is N
Any material such as iFe, NiFeNb, NiFeMo, etc. may be used as long as it is usually used for the backing layer of this type of magnetic recording medium.

The thickness of such a backing layer is preferably 0.1 μm or more and 10 μm or less. When the thickness of the backing layer is smaller than 0.1 μm, the magnetic flux is less likely to form a closed loop between the single magnetic pole head, the perpendicular magnetic recording layer, and the soft magnetic backing layer as the reluctance of the backing layer increases. A good reproduction output cannot be obtained, and when the thickness of the backing layer is larger than 10 μm, the internal stress of the film increases and cracks easily occur in the film.

The magnetic film used in the present invention is CoCr,
Any material, such as CoCrTa and CoPt, can be used as long as it is normally used in the perpendicular magnetic recording layer of this type of magnetic recording medium. The optimum value of the thickness of such a perpendicular magnetic recording layer varies depending on the wavelength of the signal to be recorded, the head used, etc., but is preferably 50 nm or more.

When the thickness of the magnetic film is smaller than 50 nm, the residual magnetization amount when a signal is recorded on the magnetic film becomes extremely small, which causes a problem that the reproduction output of the signal remarkably deteriorates.

In the magnetic disk used in the present invention, it is preferable that a protective film layer mainly containing C, ZrO ₂ , SiO ₂ or the like is formed in the surface layer portion of the magnetic layer in the range of 10 nm to 50 nm.

When the thickness of the protective film is smaller than 10 nm, the durability of the magnetic disk when the magnetic head is contact-started / stopped with respect to the magnetic disk in an actual hard disk drive (so-called general C
When the thickness of the protective film is greater than 50 nm, the so-called “generally deteriorates SS characteristics” and the magnetic film easily becomes rusted. There is a problem that the so-called void loss increases and the reproduction output significantly deteriorates.

[0054]

As is clear from the above results, a perpendicular magnetic recording layer of Co--Cr or the like having a magnetic anisotropy at least in the substrate vertical direction and a soft magnetic backing layer of permalloy or the like are formed on a non-magnetic substrate. In a so-called perpendicular magnetic recording medium having a magnetic layer etching type perpendicular magnetic recording disk in which at least a part of a data track or a servo signal portion is magnetically separated by a lithographic method or the like, a perpendicular magnetic field is formed in the concave portion. By removing only the magnetic recording layer portion, a high DC magnetization reproduction signal output can be obtained, and in the magnetic recording disk, one disk or a plurality of disks can be simultaneously batched in the disk vertical direction. Then, by applying a DC magnetic field, the magnetic recording method of collectively DC-magnetizing the perpendicular magnetic recording layer of each magnetic recording disk is used. I, since it becomes possible to perform DC magnetization recorded at a high speed in a magnetic recording disk, it is possible to apply to the mass production of the magnetic disk device having a high storage capacity, its industrial value is very large.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a magnetic recording disk used in this experiment and its concavo-convex pattern.

FIG. 2 is a conceptual diagram (Example 1) of a cross section in the circumferential direction of a magnetic recording disk according to the present example.

FIG. 3 is a conceptual diagram (Example 2) of an example of a magnetic recording method according to the present invention.

FIG. 4 is a graph showing the normalized magnetic field dependence of the direct-current magnetization reproduction output of the magnetic layer unevenness type perpendicular magnetic recording disk according to the present invention (Example 3 and Comparative Example 3).

FIG. 5 is a conceptual diagram of a cross section in the circumferential direction of a conventional magnetic layer concavo-convex perpendicular magnetic recording disk (Comparative Example 1).

[Explanation of symbols]

 1 Substrate 2 High Permeability Backing Layer 3 Perpendicular Magnetic Recording Layer 4 Magnetic Recording Convex 5 Absent

Claims (3)

[Claims] 1. A so-called perpendicular magnetic recording medium comprising a perpendicular magnetic recording layer of CoCr or the like having magnetic anisotropy at least in the substrate vertical direction and a soft magnetic backing layer of permalloy or the like on a non-magnetic substrate. In a magnetic layer etching type perpendicular magnetic recording disk in which at least a part of a data track or a servo signal part is magnetically formed in a concavo-convex manner by a lithography method or the like, only the perpendicular magnetic recording layer part is removed in the concave part. A magnetic recording disk characterized by: 2. The magnetic recording disk according to claim 1, wherein a direct current magnetic field is applied to one or a plurality of disks simultaneously in the disk vertical direction at a time, thereby perpendicularizing each magnetic recording disk. A magnetic recording method characterized by collectively magnetizing a magnetic recording layer by direct current. 3. The magnetic recording method according to claim 2, wherein
Magnetic recording disk The perpendicular coercive force of the perpendicular magnetic recording layer is set to H
A magnetic recording method characterized in that a direct current magnetic field larger than Hc + 0.5 Ms is used when c (A / m) and the saturation magnetization amount are Ms (A / m).