JPH0573878A - Perpendicular magnetic disk - Google Patents

Abstract

PURPOSE:To provide the perpendicular magnetic disk having excellent recording and reproducing characteristics to allow high reproducing output to be obtd. over the entire surface of the magnetic disk varying in a head floating quantity between the inner peripheral part side and the outer peripheral part side relating to the perpendicular magnetic disk to be used for a magnetic disk device for recording and reproducing information by being combined with floating type magnetic head. CONSTITUTION:This perpendicular magnetic disk has two-layered films consisting of a soft magnetic lining layer 12 having high magnetic permeability and a perpendicular recording layer 21 consisting of Co-Cr on a disk substrate 11 and information is recorded and reproduced on it with the floating type magnetic head. The satd. magnetic flux density on the perpendicular recording layer 21 consisting of the above-mentioned Co-Cr is so set as to be high in the inner peripheral part 21a of the disk and to be low in the outer peripheral part 21b of the disk.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a perpendicular magnetic disk used in a magnetic disk device for recording / reproducing information in combination with a floating magnetic head.

In recent years, due to an increase in the amount of information processing in a computer system, information recording on a magnetic disk device used as an external storage device has also increased, and a smaller size and a larger capacity have been promoted, and a high density recording is required. Has been done.

Along with this, as a magnetic disk, for example, a magnetic recording layer of a type capable of much higher density recording than a magnetic disk of a horizontal magnetic recording type in which information is recorded by magnetizing the magnetic recording layer in the horizontal direction. As a magnetic disk for recording information by forming remanent magnetization in the direction perpendicular to the film thickness of the magnetic disk, a perpendicular magnetic recording type magnetic disk having a double-layer structure in which a soft magnetic backing layer having a high magnetic permeability and a magnetic recording layer are laminated. Has been proposed and is being put to practical use.

In such a perpendicular magnetic disk, since the peripheral speeds of the inner peripheral portion and the outer peripheral portion during rotation are different, the flying height of the magnetic head flying above the perpendicular magnetic disk is also different between the inner peripheral portion and the outer peripheral portion. Since it changes in proportion to the peripheral speed, it tends to be difficult to obtain high reproduction output and recording density over the entire surface of the magnetic recording layer. Therefore, there is a demand for a perpendicular magnetic disk capable of obtaining a high reproduction output and recording density over the entire surface of such a magnetic recording layer.

[0005]

2. Description of the Related Art A conventional perpendicular magnetic disk, that is, a perpendicular magnetic disk having a double-layered film structure is a non-magnetic disk composed of an aluminum disk having a NiP plated surface, as shown in the cross-sectional view of the main part of FIG. A high permeability soft magnetic backing layer 12 made of, for example, a Ni-Fe alloy film having a thickness of 1 μm and a perpendicular recording layer 13 made of Co-Cr having a thickness of 0.15 μm are laminated on a substrate 11 by a sputtering method. It consists of a composition.

[0006]

By the way, in the perpendicular recording system in which the perpendicular magnetic disk having the double-layer film structure and the single magnetic pole type perpendicular magnetic head as described above are combined, the output at the time of reproduction is the same as that of the perpendicular magnetic disk. As the saturation magnetic flux density (Bs) of the perpendicular recording layer 13 increases, the saturation magnetic flux density increases with the saturation magnetic flux density value, and when the reproduction output is saturated, the saturation magnetic flux density (Bs) value decreases the head flying height. It tends to increase with the increase.

Therefore, in order to increase the reproduction output in lowering the flying height of the perpendicular magnetic head, it is necessary to increase the saturation magnetic flux density (Bs) value of the perpendicular recording layer 13. However, an excessively high saturation magnetic flux density of the perpendicular recording layer 13 lowers the vertical anisotropy, and therefore a steeper head magnetic field than that of the magnetic head during recording cannot be obtained, which causes a problem of lowering the recording density. is there.

Further, the peripheral speed at the radial position of the perpendicular magnetic disk rotating at a constant speed is different, and the peripheral speed inevitably increases from the inner peripheral portion to the outer peripheral portion, and the perpendicular magnetic disk is proportionally increased. The flying height of the magnetic head that floats on the disk is small at the inner peripheral portion and changes greatly toward the outer peripheral portion.

Therefore, when the saturation magnetic flux density (Bs) value of the perpendicular recording layer 13 of the perpendicular magnetic disk is set relatively high,
High reproduction output is obtained at the inner peripheral portion where the head flying height on the disk surface is low, while on the other hand, the saturation magnetic flux density (Bs) value at which the reproduction output is saturated at the outer peripheral portion where the head flying height is high is the perpendicular recording layer 13 Original saturation magnetic flux density (Bs) set to
Since it is lower than the value, it is not possible to obtain the reproduction output corresponding to the saturation magnetic flux density (Bs) set to a relatively high value, and the perpendicular anisotropy is lowered and the head magnetic field is steeper than the perpendicular magnetic head. Cannot be performed, and the recording density decreases.

When the saturation magnetic flux density (Bs) value of the perpendicular recording layer 13 is set to be relatively low so that a high reproduction output can be obtained in the outer peripheral portion where the head flying height on the disk surface is high, the head flying height is low. There is a problem that a high reproduction output cannot be obtained in the inner peripheral part.

In view of the above conventional problems, the present invention has an excellent recording / reproducing characteristic that a high reproducing output can be obtained over the entire surface of a magnetic disk having different head flying heights on the inner peripheral side and the outer peripheral side of the disk surface. The object is to provide a new perpendicular magnetic disk.

[0012]

In order to achieve the above-mentioned object, the present invention has a two-layer film including a soft magnetic backing layer having a high magnetic permeability and a perpendicular recording layer made of Co-Cr on a disk substrate, In a perpendicular magnetic disk in which information is recorded / reproduced by a floating magnetic head, the saturation magnetic flux density of the perpendicular recording layer made of Co-Cr is set to be high at the inner circumference of the disk and low at the outer circumference of the disk. And

Further, the saturation magnetic flux density is a value of the saturation magnetic flux density when the reproduction output is saturated at a varying head flying height. In addition, the above-mentioned Co-Cr perpendicular recording layer Cr
The content concentration is set to be low at the inner peripheral portion of the disc and high at the outer peripheral portion of the disc.

[0014]

In the magnetic disk of the present invention, as a result of investigating the relationship between the saturation magnetic flux density (Bs) and the head flying height of the perpendicular recording layer made of Co-Cr and the reproduction output or the recording density,
Change in head flying height with respect to magnetic disk, saturation magnetic flux density (Bs) of perpendicular recording layer, and standardized output (playback output)
As is clear from FIG. 2 showing the relationship with the above, when the head flying height decreases from 0.13 μm to 0.06 μm, for example, the saturation magnetic flux density (Bs) value of the perpendicular recording layer at which the reproduction output is saturated is about 3500 Gauss. It increases to 4500 Gauss and the reproduction output value increases accordingly.

Further, the change of the head flying height with respect to the magnetic disk and the saturation magnetic flux density (Bs) and recording density of the perpendicular recording layer
As is clear from FIG. 3 showing the relationship with (D ₅₀ : recording density when reproduction output becomes half of solitary wave output), as the head flying height increases, the recording density (D ₅₀ ) decreases and perpendicular recording Recording density increases as the saturation magnetic flux density (Bs) of the layer increases.
(D ₅₀ ) decreases.

From these figures, the change in the saturation magnetic flux density (Bs) depending on the flying height of the head has a remarkable effect on the recording / reproducing characteristics. Therefore, the saturation magnetic flux density (Bs) value of the perpendicular recording layer is changed according to the flying height of the head. It is necessary to set it optimally.

Therefore, based on FIG. 4 showing the relationship between the head flying height and the saturation magnetic flux density (Bs) value when the reproduction output is saturated, the saturation of the perpendicular recording layer in the disk radial direction where the head flying height changes. By setting the magnetic flux density (Bs) to the optimum value corresponding to the changing head flying height, a high reproduction output can be obtained over the entire disc surface, and the decrease in recording density due to the decrease in vertical anisotropy is minimized. Therefore, the perpendicular magnetic disk having excellent recording / reproducing characteristics can be obtained.

[0018]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a cross-sectional view of essential parts showing an embodiment of a perpendicular magnetic disk according to the present invention.

In the figure, 11 is a non-magnetic disk substrate made of an aluminum disk or the like having a surface plated with NiP. On the disk substrate 11, a Ni-film having a film thickness of 1 μm is formed on the disk substrate 11 by a sputtering method or the like as in the conventional case. A high magnetic permeability soft magnetic backing layer 12 made of an Fe alloy film is deposited, and the Cr content concentration on the surface of the soft magnetic backing layer 12 is as low as 20 at% in the inner peripheral portion 21a,
A Co-Cr film having a thickness of 0.15 μm having a Cr content concentration gradient that gradually changes so that the Cr content concentration in the outer periphery portion 21b increases from the inner periphery portion 21a toward the outer periphery portion 21b.
The perpendicular recording layer 21 made of is laminated.

With such a disk structure, the saturation magnetic flux density (Bs) of the perpendicular recording layer 21 is, for example, 4500 Gauss in the inner peripheral portion 21a where the head flying height is low, and the head flying height is increased from the inner peripheral portion 21a. It is set so that the saturation magnetic flux density (Bs) at the outer peripheral portion 21b decreases as it goes down toward the outer peripheral portion 21b where the amount becomes higher, and the inner peripheral portion of the perpendicular recording layer 21 is reduced. High reproduction output and high recording density are obtained at 21a, and reproduction output and recording density almost the same as those of the inner peripheral portion 21a are also obtained at the outer peripheral portion 21b.
Recording / reproducing characteristics are improved over the entire surface of the disc.

The saturation magnetic flux density (Bs) described above is calculated by
The perpendicular recording layer 21 is changed to be lower toward the outer peripheral portion 21b than 21a.
As a method of forming a film, a soft magnetic backing layer 12 having a high magnetic permeability is formed based on the relationship between the Cr content and the substrate temperature and the saturation magnetic flux density (Bs) when forming the perpendicular recording layer shown in FIG. In the moving direction of the non-magnetic disk substrate 11 deposited, the disk substrate is moved.
A first mask source having a first mask plate having an annular opening corresponding to the inner peripheral portion of 11 and a first Co—Cr target having a Cr content of 20 at%, and a circle corresponding to the outer peripheral portion of the disk substrate 11. Second mask plate with annular opening and Cr content 24at
% Of a second Co-Cr target and a second sputtering source provided in parallel, first, the disk substrate 11 is moved in a state of being heated to 150 ° C. so as to face the first sputtering source, After sputtering the first Co—Cr target with a Cr content of 20 at%, 220
The soft magnetic backing layer 12 has a Cr content concentration on the inner periphery thereof by moving it while being heated to ℃, facing the second sputtering source, and sputtering a second Co—Cr target having a Cr content of 24 at%. It is possible to form the perpendicular recording layer 21 made of Co—Cr having the desired saturation magnetic flux density (Bs) distribution that is low at the portion 21a and gradually increases toward the outer peripheral portion 21b.

Further, the saturation magnetic flux density (Bs) described above is set to the inner peripheral portion.
The perpendicular recording layer 21 is changed to be lower toward the outer peripheral portion 21b than 21a.
As another method of forming the film, for example, a non-magnetic disk substrate 11 in which a soft magnetic backing layer 12 having a high magnetic permeability is adhered to a first Co—Cr target having a Cr content of 20 at% is disposed so as to face the disk. After the substrate 11 is heated to 220 ° C., it is sputtered through a first mask plate having an annular opening corresponding to the inner peripheral portion of the disc substrate 11, and then the disc substrate 11 is heated to 50 ° C. By depositing the perpendicular recording layer 21 made of Co-Cr by the method of sputtering through the second mask plate having the annular opening corresponding to the outer peripheral portion of the disk substrate 11, the Cr content concentration is also increased in the inner peripheral portion. Co-Cr having a desired saturation magnetic flux density (Bs) distribution that is low at 21a and gradually increases toward the outer peripheral portion 21b.
It is possible to form the perpendicular recording layer 21 of.

In the above embodiment, the saturation magnetic flux density (Bs) from the inner peripheral portion to the outer peripheral portion of the perpendicular recording layer was set to 4500 to 3500 Gauss.
However, the present invention is not limited to this example, and it is possible to optimally set the saturation magnetic flux density (Bs) value from the inner peripheral portion to the outer peripheral portion in accordance with the flying height of the head. Needless to say.

[0024]

As is apparent from the above description, according to the perpendicular magnetic disk of the present invention, the saturation magnetic flux density (B
s) is set to the optimum value corresponding to the varying head flying height, the high read output over the entire disk surface and the recording density resulting from the reduction of the vertical anisotropy due to the excessive saturation magnetic flux density (Bs). Has a merit that it is possible to realize a perpendicular magnetic disk having excellent recording / reproducing characteristics in which the deterioration of the magnetic field is suppressed to a minimum, and has a remarkable effect in practical use.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing an embodiment of a perpendicular magnetic disk according to the present invention.

FIG. 2 is a diagram showing a relationship between a change in head flying height, a saturation magnetic flux density (Bs) of a perpendicular recording layer, and a normalized output (reproduction output).

FIG. 3 is a diagram showing the relationship between the change in head flying height and the saturation magnetic flux density (Bs) and recording density (D ₅₀ ) of the perpendicular recording layer.

FIG. 4 is a diagram showing a relationship between a head flying height and a saturation magnetic flux density (Bs) value when a reproduction output is saturated.

FIG. 5 is a diagram showing the relationship between the Cr content and the substrate temperature at the time of forming the perpendicular recording layer and the saturation magnetic flux density (Bs).

FIG. 6 is a sectional view of relevant parts for explaining a conventional perpendicular magnetic disk.

[Explanation of symbols]

 11 Disk Substrate 12 Soft Magnetic Backing Layer 21 Perpendicular Recording Layer 21a Inner Perimeter 21b Outer Perimeter

Claims (3)

[Claims] 1. A disk substrate (11) has a two-layer film comprising a high magnetic permeability soft magnetic backing layer (12) and a perpendicular recording layer (21) made of Co-Cr. In the perpendicular magnetic disk on which is recorded and reproduced, the saturation magnetic flux density of the perpendicular recording layer (21) made of Co-Cr is
A perpendicular magnetic disk characterized in that the inner circumference (21a) of the disk is high and the outer circumference (21b) of the disk is low. 2. The perpendicular magnetic disk according to claim 1, wherein the saturation magnetic flux density is a value of the saturation magnetic flux density when the reproduction output is saturated at a varying head flying height. 3. The perpendicular recording layer (21) made of Co-Cr is Cr.
2. The perpendicular magnetic disk according to claim 1, wherein the content concentration is set to be low at the disk inner peripheral portion (21a) and high at the disk outer peripheral portion (21b).