JP4082590B2 - Demagnetizing method and manufacturing method for perpendicular magnetic recording disk, and demagnetizing device for perpendicular magnetic recording disk - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for demagnetizing a perpendicular magnetic recording disk mounted on a magnetic disk device such as a perpendicular magnetic recording system HDD (hard disk drive), a method for manufacturing a perpendicular magnetic recording disk including the demagnetizing method, and an implementation thereof. The present invention relates to a demagnetizing device.
[0002]
[Prior art]
Usually, in manufacturing a magnetic disk, it is manufactured through the following processes and shipped to the market. That is, it includes a disk substrate manufacturing process, a film forming process, an inspection process, a demagnetizing process, and a shipping process. Thereafter, it is assembled and completed as an HDD by an HDD (hard disk drive) manufacturing process.
Here, the demagnetization process is a magnetization signal generated or recorded on the disk surface by a previous process so as not to cause a failure in a subsequent process (for example, a servo write process or a clock write process in the HDD manufacturing process). And a process of eliminating noise.
Examples of the signal and noise to be erased include a test pattern signal recorded during recording / reproduction inspection and signal quality inspection in the inspection process, and noise (most of which is AC noise) generated in the film formation process.
As an erasing method, a DC erasing method or an AC erasing method is used. (For example, Patent Document 1)
[0003]
[Patent Document 1]
JP-A-10-105901 [0004]
[Problems to be solved by the invention]
In recent years, magnetic disk devices such as HDDs have rapidly increased their recording capacity with the development of the IT industry. With recent magnetic disks, a recording capacity of 60 gigabits or more per square inch is becoming feasible.
Such a high information capacity is realized by improving the information recording density of the magnetic disk.
However, when trying to realize such a high information recording density, a longitudinal magnetic recording method (longitudinal magnetic recording method or horizontal magnetic recording method), which is a recording method for HDDs and magnetic disks currently on the market, is also called. ) Has proved difficult to realize due to factors such as the manifestation of thermal fluctuation disturbances.
[0005]
In order to solve this problem, a magnetic disk for the perpendicular magnetic recording system has been actively researched instead of the in-plane magnetic recording system. This is because the perpendicular magnetic recording system is less susceptible to thermal fluctuations and is suitable for increasing the recording density.
However, in the perpendicular magnetic recording disk, since the design concept such as the film material and the film thickness is significantly different from that of the currently popular in-plane magnetic recording disk, the manufacturing cost is increased. Instead, there is a problem that the spread to the market is hindered.
[0006]
By the way, as a demagnetizing method for a perpendicular magnetic recording disk, no new method has been implemented at present, and a permanent magnet similar to a conventional general in-plane magnetic recording disk (also referred to as a longitudinal magnetic recording disk) is used. It is considered that the spiral type demagnetization method can be applied. As a conventional spiral-type degaussing method using a permanent magnet for a longitudinal magnetic recording disk, for example, the technique of Patent Document 1 can be cited.
[0007]
Here, a typical demagnetization method for a longitudinal magnetic recording disk will be described with reference to FIG.
In the case of a longitudinal magnetic recording disk, as shown in FIG. 10, a magnetic disk 31 is mounted on a spindle motor 35 and rotated, and a magnetic field in a direction along the disk surface from the magnetic pole of the permanent magnet 30 (parallel to the disk surface). The permanent magnet 30 is moved from the inner peripheral side of the magnetic disk 31 to the outer peripheral side, or from the outer peripheral side to the inner peripheral side, while this magnetic field acts on the magnetic disk 31 against the disk surface. By moving it, as shown in FIG. 11, the magnet trajectory (= demagnetization trajectory) 33 is spirally drawn on the magnetic disk 31 and demagnetized.
[0008]
However, when the same method as the conventional longitudinal magnetic recording disk described above is applied to demagnetization of a perpendicular magnetic recording disk, for example, in the case of a 2.5 inch type magnetic disk, about 10 seconds are required to erase the entire disk surface. It will take a long time.
Further, in order to reliably prevent the occurrence of unerased, it is necessary to provide a region that overlaps slightly at the edge portion of the magnet, so that additional time is required, and eventually it takes too much demagnetization time. There's a problem.
[0009]
In consideration of the above circumstances, the present invention provides a demagnetizing method and demagnetizing device for a perpendicular magnetic recording disk that can demagnetize the entire disk easily and at a much higher speed than conventional demagnetizing methods for longitudinal magnetic recording media. It is a first object to provide
Furthermore, by providing a method for manufacturing a perpendicular magnetic recording disk having a short manufacturing tact, that is, high production efficiency, based on the demagnetizing method or demagnetizing apparatus of the present invention, it is possible to provide an inexpensive perpendicular magnetic recording disk, A second object is to contribute to the spread of recording disks.
[0010]
[Means for Solving the Problems]
The inventors focused on the recording / reproducing method of the perpendicular magnetic recording disk, and conducted research on whether a simple and high-performance demagnetizing method for the perpendicular magnetic recording disk could be developed by using this recording / reproducing method. The inventors have found that the above-mentioned problems can be solved by the following invention, and have completed the present invention.
The present invention has the following configuration.
(Configuration 1)
A ring-shaped magnetic pole that generates a magnetic field perpendicular to the main surface of the perpendicular magnetic recording disk and that is paired across the disk surface is enlarged or reduced in diameter in the radial direction of the disk surface.
A method of demagnetizing a perpendicular magnetic recording disk, wherein a magnetic pole is moved to erase a recording signal and / or noise on the main surface .
(Configuration 2)
The perpendicular magnetic recording disk according to Configuration 1, wherein at least a soft magnetic underlayer and a ferromagnetic perpendicular magnetic recording layer are formed on a disk substrate.
(Configuration 3)
A method for manufacturing a perpendicular magnetic recording disk, comprising a demagnetizing step including the method for demagnetizing a perpendicular magnetic recording disk according to Configuration 1 or 2.
(Configuration 4)
A ring-shaped magnetic pole that generates a magnetic field perpendicular to the main surface of a perpendicular magnetic recording disk and that is paired across the disk surface is expanded or contracted to move the magnetic pole in the radial direction of the disk surface. A demagnetizing device for a perpendicular magnetic recording disk, wherein the recording signal and / or noise on the main surface is erased.
The present invention further includes the following configurations.
(Configuration 5)
A method for demagnetizing the perpendicular magnetic recording disk according to Configuration 1, comprising:
A ring that forms a pair with the upper and lower surfaces of the perpendicular magnetic recording disk with the perpendicular magnetic recording disk interposed therebetween, and that can be enlarged and reduced in diameter, and that generates a magnetic field perpendicular to the perpendicular magnetic recording disk surface. The perpendicular magnetic recording is characterized in that a disk-shaped magnet is disposed and the ring-shaped magnet is expanded or contracted to move the magnet in the radial direction of the perpendicular magnetic recording disk to demagnetize the disk surface. How to demagnetize the disk.
(Configuration 6)
The perpendicular magnetic recording disk according to any one of configurations 1 to 3, wherein a pinned layer for fixing the magnetization of the soft magnetic underlayer is formed between the disk substrate and the soft magnetic underlayer. Degaussing method of magnetic recording disk.
(Configuration 7)
A demagnetizing device for a perpendicular magnetic recording disk according to Configuration 4,
A ring that forms a pair with the upper and lower surfaces of the perpendicular magnetic recording disk with the perpendicular magnetic recording disk interposed therebetween, and that can be enlarged and reduced in diameter, and that generates a magnetic field perpendicular to the perpendicular magnetic recording disk surface. A magnet moving mechanism for demagnetizing the disk surface by moving the magnet in the radial direction of the perpendicular magnetic recording disk by expanding or reducing the diameter of the ring-shaped magnet. A demagnetizing device for a perpendicular magnetic recording disk.
(Configuration 8)
A demagnetizing device for a perpendicular magnetic recording disk according to Configuration 7,
As the ring-shaped magnet, a chain-shaped magnet that is deformable between two modes of a reduced-diameter shape and an enlarged-diameter shape by connecting a large number of small magnets in a freely rotatable manner is used. To demagnetize perpendicular magnetic recording disks.
(Configuration 9)
A demagnetizing device for a perpendicular magnetic recording disk according to claim 7,
A demagnetizing device for a perpendicular magnetic recording disk, wherein an elastic magnet whose circumference can be expanded and contracted is used as the ring-shaped magnet.
[0011]
The method of demagnetizing a perpendicular magnetic recording disk according to the present invention, for example, as shown in FIG. 1, is performed by sandwiching the perpendicular magnetic recording disk 1 between both main surfaces (upper surface and lower surface in FIG. 1). And a ring-shaped magnetic pole (for example, a magnet) that generates a magnetic field perpendicular to the disk surface through the disk surface with respect to the surface of the perpendicular magnetic recording disk. ) 2 and the ring-shaped magnetic pole 2 is enlarged or reduced in diameter, the magnetic pole 2 can be moved in the radial direction on the surface of the perpendicular magnetic recording disk 1 to demagnetize the disk surface.
[0012]
In this case, in order to generate a magnetic field perpendicular to the surface of the perpendicular magnetic recording disk 1, the magnetic poles on both main surfaces (upper surface and lower surface in FIG. 1) have magnetizations reversed from each other. Specifically, the N pole (S pole) of the top magnetic pole and the S pole (N pole) of the bottom magnetic pole are made to face each other.
By adopting such a demagnetizing method, it is possible to carry out a demagnetizing method using the characteristics of the perpendicular magnetic recording disk easily and at high speed.
[0013]
Based on the degaussing method of the present invention, the recording signal and / or noise of the perpendicular magnetic recording layer formed on the perpendicular magnetic recording disk can be erased efficiently.
In particular, when the paired magnetic poles move on the disk surface, DC erasure (direct current erasure) can be performed by fixing the magnetization of the magnetic poles (having magnetizations reversed with respect to each other) on the paired main surfaces. Become. By performing DC erasure, the perpendicular magnetic recording layer is uniformly erased by the DC component, so that the test pattern signal recorded during the recording / reproduction inspection and the signal quality inspection, and noise generated during the film formation process In many cases, AC noise) can be reliably eliminated.
[0014]
As an aspect of the degaussing device for realizing the demagnetizing method of the perpendicular magnetic recording disk of the present invention, for example, both main surfaces (for example, the upper surface and the lower surface) of the perpendicular magnetic recording disk are paired with the perpendicular magnetic recording disk interposed therebetween. A ring-shaped magnetic pole (for example, a magnet) capable of expanding and contracting and generating a magnetic field perpendicular to the perpendicular magnetic recording disk surface is disposed, and the ring-shaped magnetic pole is expanded or contracted. Thus, there is an embodiment in which a magnet moving mechanism for moving the magnetic pole in the radial direction of the perpendicular magnetic recording disk and demagnetizing the disk surface is provided.
[0015]
Specifically, as the ring-shaped magnetic pole, a chain-shaped magnet that can be deformed between two modes of a reduced-diameter shape and an enlarged-diameter shape by connecting a large number of small magnets rotatably is used. The aspect which used the elastic body magnet which circumference length can expand / contract as said ring-shaped magnetic pole and said ring-shaped magnetic pole can be mentioned preferably.
According to the present invention, since the magnetic pole is moved in the radial direction of the perpendicular magnetic recording disk by expanding or reducing the diameter of the ring-shaped magnetic pole (for example, magnet), the entire surface of the disk can be obtained without rotating the perpendicular magnetic recording disk. Can be demagnetized at high speed without any remaining unerased.
In addition, since the present invention does not require the rotational operation of the disk, even if the disk substrate is a glass disk, for example, there is no danger of scratching and cracking and scattering of fragments. The protective cover for prevention can also be omitted. A ring-shaped magnet (permanent magnet or electromagnet) can be arranged as the ring-shaped magnetic pole.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 2 shows the configuration of the ring-shaped magnet 12 in the degaussing device of the first embodiment. This ring-shaped magnet 12 is formed in a chain shape as shown in (a) by sequentially connecting a large number of small magnets 12a as shown in (b), and is reduced in diameter by being folded. It becomes a shape and becomes a diameter-expanded shape by expanding. Then, the ring-shaped magnet 12 is radially expanded (in the direction of the arrow) from the outer peripheral side to the inner peripheral side and from the inner peripheral side to the outer peripheral side of the perpendicular magnetic recording disk 1 by being folded or unfolded. Can be moved to.
[0017]
FIG. 3 shows an example of a magnet moving mechanism 10 that moves the ring-shaped magnet 12 in the radial direction of the perpendicular magnetic recording disk 1 by expanding or reducing the diameter. In this mechanism 10, the height position of the ring-shaped magnet 12 is fixed, and can move only in the radial direction by expanding and contracting.
In order to move the ring-shaped magnet 12, the magnet moving mechanism 10 adopts an umbrella-bone-like structure. That is, the magnet moving mechanism 10 includes a guide rod 13 disposed on the center line of the perpendicular magnetic recording disk 1, and a slide ring 14 provided on the guide rod 13 so as to be slidable up and down. The base end of each aggregate 15 is connected, and a ring-shaped magnet 12 is connected to the tip of each aggregate 15 so as to be rotatable.
[0018]
According to the magnet moving mechanism 10, as shown in (a), the ring-shaped magnet 12 can be narrowed (reduced in diameter) by sliding the slide ring 14 upward. Moreover, as shown in (b), by sliding the slide ring 14 downward, the ring-shaped magnet 12 can be widened (expanded shape).
In the degaussing device of this embodiment, the ring-shaped magnet 12 is disposed so as to be paired with each other on both main surfaces (for example, an upper surface and a lower surface) of the perpendicular magnetic recording disk 1. The magnet moving mechanism 10 is also arranged in the same manner. In this case, the ring-shaped magnets 12 on the upper and lower surfaces of the perpendicular magnetic recording disk 1 are arranged with magnetic poles so as to generate a magnetic field perpendicular to the perpendicular magnetic recording disk surface. Further, the upper and lower magnet moving mechanisms 10 are linked by the interlocking means so that the upper and lower ring-shaped magnets 12 move in a paired manner.
[0019]
In such a configuration, the ring-shaped magnet 12 is expanded or contracted by the sliding operation of the slide ring 14 of the magnet moving mechanism 10. Then, by moving the ring-shaped magnet 12 in the radial direction of the perpendicular magnetic recording disk 1, the entire surface of the disk can be demagnetized without being erased at high speed without rotating the perpendicular magnetic recording disk 1. Also, since the perpendicular magnetic recording disk 1 does not need to rotate, there is no danger of cracking and scattering even if the glass disk is scratched. You can also
In addition, although the permanent magnet is assumed as the ring-shaped magnet 12, an electromagnet can also be used.
[0020]
FIG. 4 shows the configuration of the ring-shaped magnet 22 in the degaussing device of the second embodiment. The ring-shaped magnet 22 is an elastic magnet in which a magnetic material is mixed with an elastic material that expands and contracts like rubber. As shown in (a), the ring-shaped magnet 22 has a reduced diameter shape by contracting the circumference according to its own elasticity, and a diameter-expanding shape by extending the circumference by its own elasticity. Then, by contracting or extending, the ring-shaped magnet 22 moves in the radial direction (arrow direction) from the outer peripheral side of the perpendicular magnetic recording disk 1 to the inner peripheral side and from the inner peripheral side to the outer peripheral side. Be able to. As shown in (b), the ring-shaped magnet 22 can be configured to generate a predetermined magnetic force by stacking a plurality of ring-shaped thin plate magnets 22a magnetized in the thickness direction.
[0021]
In the degaussing device according to the present embodiment, the ring-shaped magnet 22 is disposed on both main surfaces (for example, the upper surface and the lower surface) of the perpendicular magnetic recording disk 1 so as to make a pair. Further, the above-described magnet moving mechanism 10 is assembled to the ring-shaped magnet 22 and arranged in the same manner.
Also in this case, the ring-shaped magnets 22 on the upper surface and the lower surface of the perpendicular magnetic recording disk 1 arrange the magnetic poles so as to generate a magnetic field perpendicular to the perpendicular magnetic recording disk surface.
Further, the upper and lower magnet moving mechanisms 10 are linked by interlocking means so that the upper and lower ring-shaped magnets 22 move in a paired manner.
In such a configuration, by the sliding operation of the slide ring 14 of the magnet moving mechanism 10, the ring-shaped magnet 22 is expanded or contracted using the elasticity of the magnet 22 itself.
Then, by moving the ring-shaped magnet 22 in the radial direction of the perpendicular magnetic recording disk 1, the entire surface of the disk can be demagnetized without being erased at high speed without rotating the perpendicular magnetic recording disk 1. Also, since the perpendicular magnetic recording disk 1 does not need to rotate, there is no danger of cracking and scattering even if the glass disk is scratched. You can also
[0022]
The present invention can be used for a perpendicular magnetic recording disk in which at least a perpendicular magnetic recording layer is formed on a disk substrate. This is because according to the present invention, demagnetization (erase of recording signal and / or noise) of the perpendicular magnetic recording layer can be performed efficiently and in a short time.
[0023]
Furthermore, the present invention is particularly suitable for use with a perpendicular magnetic recording disk in which a soft magnetic underlayer is interposed between the disk substrate and the perpendicular magnetic recording layer. When used for a perpendicular magnetic recording disk in which a pinned layer (a layer for fixing the magnetization of the soft magnetic underlayer) is interposed between the base layer and the base layer, an excellent effect can be obtained. According to the present invention, the demagnetization of the perpendicular magnetic recording layer can be efficiently performed in a short time, and at the same time, spike noise generated by the soft magnetic underlayer can be effectively erased.
[0024]
When the demagnetization method according to the present invention is applied to the perpendicular magnetic recording disk having such a film structure, it has been confirmed that there is an action of eliminating spike-like noise generated from the soft magnetic underlayer. In the conventional demagnetization shown in FIG. 10, spike-like noise generated by the soft magnetic underlayer was seen as shown in FIG. 7A. However, as shown in FIG. Noise can be eliminated.
The reason why the spike noise disappears is considered as follows.
[0025]
In the first place, spike noise is generated when a magnetoresistive element (MR element) used for a read element of a magnetic head passes through a domain wall of a soft magnetic underlayer as shown in FIG. 8 during signal reproduction. When a conventional demagnetization method is used for a perpendicular magnetic recording disk having a soft magnetic underlayer having a magnetic anisotropy in the radial direction as shown in FIG. 6, it cannot be demagnetized, or in the circumferential direction, that is, the hard axis direction. When demagnetized, the magnetization directions are not aligned as shown in FIG. 9A, and a domain wall is generated. However, when magnetized in the radial direction, that is, the easy axis direction by the method of the present invention, the magnetization directions are aligned as shown in FIG. Even after demagnetization, the magnetization state of the soft magnetic underlayer is maintained by the pinned layer (antiferromagnetic layer). Therefore, according to the present invention, a perpendicular magnetic recording disk having a soft magnetic underlayer can be reliably demagnetized at high speed without any unerasure, and at the same time, spiked noise can be effectively demagnetized. Conceivable.
Hereinafter, a method for manufacturing a perpendicular magnetic recording disk using the degaussing method and the degaussing device of the present invention will be described with reference to examples.
[0026]
Example 1
FIG. 5 shows a schematic cross-sectional view of a perpendicular magnetic recording disk 500 of this embodiment. At least a disk substrate 51 and a perpendicular magnetic recording layer 56 on which recording and reproduction are performed are provided.
The perpendicular magnetic recording layer 56 is DC erased (DC erased) by degaussing according to the present invention.
In FIG. 5, reference numeral 51 denotes a disk substrate made of glass. An adhesion layer 52 has an action of promoting adhesion between the glass disk substrate 51 and the upper layer. Reference numeral 53 denotes a pinned layer having a function of pinning the magnetization of the soft magnetic underlayer 54. A soft magnetic underlayer 54 made of a soft magnetic material has magnetic anisotropy in the disk radial direction (that is, an easy magnetization axis is given in the radial direction), and perpendicular magnetic to the perpendicular magnetic recording layer 56. It has the function of promoting recording based on the mirror image effect. Reference numeral 55 denotes a nonmagnetic underlayer made of a nonmagnetic material and has a function of promoting the perpendicular orientation of the perpendicular magnetic recording layer 56. Reference numeral 56 denotes a perpendicular magnetic recording layer made of a ferromagnetic material. Reference numeral 57 denotes a protective layer for protecting the perpendicular magnetic recording layer 56 from impact. Reference numeral 58 denotes a lubricating layer for mitigating external impact.
Hereinafter, a method for manufacturing the perpendicular magnetic recording disk 500 of the present invention will be described.
[0027]
(Disc board manufacturing process)
First, a 2.5-inch disk (outer diameter 65 mm, inner diameter 20 mm, disk thickness 0.635 mm) made of mirror-polished aluminosilicate glass was chemically strengthened to obtain a glass disk substrate 51 for a magnetic disk.
(Film formation process)
An adhesion layer 52 to a protective layer 57 were sequentially formed on the glass disk substrate 51 by DC magnetron sputtering. First, an adhesion layer 52 of an hcp crystal structure made of Ti, an antiferromagnetic pin layer 53 made of an FeMn alloy, a soft magnetic underlayer 54 made of a CoTaZr alloy, a nonmagnetic underlayer 55 made of a NiTa alloy, and a CoPtCr alloy A perpendicular magnetic recording layer 56 and a protective layer 57 made of hydrogenated carbon were formed.
Next, an alcohol-modified perfluoropolyether lubricant was applied by a dip method to form a lubricating layer 58. A perpendicular magnetic disk formed as described above was obtained.
[0028]
(Inspection process and demagnetization process)
In order to inspect whether the obtained perpendicular magnetic recording disk has a function as a perpendicular magnetic recording disk, a glide inspection, a recording / reproducing inspection, and a signal quality inspection (error inspection) were sequentially performed. Prior to the recording / reproduction inspection, the demagnetization method of the aspect described in FIG. 2 was performed, and the noise generated during film formation (most of which was AC noise) was DC erased. Further, before the signal quality inspection, the demagnetization method was performed in the manner described with reference to FIG. 2, and the recording signal and noise during the recording / reproduction inspection were DC erased. Finally, the degaussing method of the aspect described in FIG. 4 was performed, and the recording signal and noise at the time of signal quality inspection were DC erased.
Since the time required for each demagnetization method was 1 second each, the entire demagnetization process required 3 seconds.
In the inspection process, no defect was found in the perpendicular magnetic recording disk, and it was found that the perpendicular magnetic recording disk was a good quality. Further, after the erasing process, the remaining recording signal or the like generated by the perpendicular magnetic recording layer was not observed, and the AC noise was erased with the DC noise remaining. Further, no spike noise generated by the soft magnetic underlayer was observed. When demagnetization was performed based on the demagnetization method of the longitudinal magnetic recording medium (in-plane magnetic recording medium) described with reference to FIG. 10, each demagnetization required 10 seconds, and therefore the entire demagnetization process required 30 seconds. did.
[0029]
In other words, if the demagnetization of the present invention is used, in the case of this embodiment, the time loss required for demagnetization can be shortened by 27 seconds per 2.5 inch type disk.
In this case, if 1000 discs are to be manufactured, the time can be shortened to 27000 seconds, that is, 7 hours and 30 minutes, so that it is possible to shorten the work time for almost one day.
Thus, the perpendicular magnetic recording disk 10 that can be shipped was completed. After that, the perpendicular magnetic recording disk was stored in a case, vacuum packed, and shipped to the market.
[0030]
As the layer material of the perpendicular magnetic recording disk of the present invention, for example, a TiCr alloy or the like may be selected as the adhesion layer 2 in addition to Ti. In addition to the FeMn alloy, an IrMn alloy, a PtMn alloy or the like may be selected as the pinned layer 3, and as the soft magnetic underlayer 4, an FeCoB alloy or NiFe alloy may be selected in addition to the CoTaZr alloy. May be. Furthermore, as the nonmagnetic underlayer 5, for example, a CrTi alloy or a Ru alloy may be selected. As the perpendicular magnetic recording layer 6, for example, a CoPtCrTa alloy or a CoPtCrB alloy may be selected in addition to the CoPtCr alloy.
[0031]
【The invention's effect】
As described above, according to the present invention, demagnetization (erasing of recording signals and / or noise) of a perpendicular magnetic recording disk can be provided by an efficient and simple method, thereby increasing the production efficiency of the perpendicular magnetic recording disk. Thus, an inexpensive perpendicular magnetic recording disk can be provided.
[Brief description of the drawings]
1A and 1B are diagrams used for explaining the principle of the present invention, in which FIG. 1A is a side view and FIG. 1B is a plan view;
FIGS. 2A and 2B are explanatory views of a ring-shaped magnet in the degaussing device according to the first embodiment of the present invention, in which FIG. 2A is a plan view and FIG. 2B is an enlarged perspective view of its elements.
3A and 3B are schematic views of a magnet moving mechanism in the demagnetizing device, in which FIG. 3A is a perspective view showing a state in which the diameter of a ring-shaped magnet is reduced, and FIG.
4A and 4B are explanatory diagrams of a ring-shaped magnet in a demagnetizing device according to a second embodiment of the present invention, in which FIG. 4A is a plan view, and FIG. 4B is an enlarged view of its elements; It is an arrow view.
FIG. 5 is an explanatory diagram showing an example of a film configuration of a perpendicular magnetic recording disk.
FIG. 6 is an explanatory diagram of the magnetic anisotropy direction of the soft magnetic underlayer.
FIG. 7 is a diagram showing a difference in demagnetization effect between a conventional degaussing method and a degaussing method of the present invention.
FIG. 8 is an explanatory diagram of spike noise and domain walls.
FIG. 9 is a diagram showing a comparison between a magnetization direction and a domain wall after demagnetization by a conventional demagnetization method and a demagnetization method of the present invention.
FIG. 10 is a side view for explaining a conventional demagnetization method.
FIG. 11 is a plan view for explaining a conventional demagnetization method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Perpendicular magnetic recording disk 2 Ring-shaped magnet 12 Chain-shaped magnet 10 Magnet moving mechanism 22 Elastic body magnet 51 Disk substrate 52 Adhesion layer 53 Pin layer 54 Soft magnetic underlayer 55 Nonmagnetic underlayer 56 Perpendicular magnetic recording layer 57 Protective layer 58 Lubricating layer 500 Perpendicular magnetic recording disk

Claims (4)

A ring-shaped magnetic pole that generates a magnetic field perpendicular to the main surface of a perpendicular magnetic recording disk and that is paired across the disk surface is expanded or contracted to move the magnetic pole in the radial direction of the disk surface. A method for demagnetizing a perpendicular magnetic recording disk, wherein the recording signal and / or noise on the main surface is erased.   2. A method for demagnetizing a perpendicular magnetic recording disk according to claim 1, wherein at least a soft magnetic underlayer and a ferromagnetic perpendicular magnetic recording layer are formed.   A method for manufacturing a perpendicular magnetic recording disk, comprising a degaussing step including the method for demagnetizing a perpendicular magnetic recording disk according to claim 1.   A ring-shaped magnetic pole that generates a magnetic field perpendicular to the main surface of a perpendicular magnetic recording disk and that is paired across the disk surface is expanded or contracted to move the magnetic pole in the radial direction of the disk surface. A demagnetizing device for a perpendicular magnetic recording disk, wherein the recording signal and / or noise on the main surface is erased.

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