JP2002279615A - Magntic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a satisfactory recording and reproducing characteristics corresponding to high recording density. SOLUTION: A magnetic domain controlling layer 12 consisting of a Mn based anti-ferromagnetic material, an intermediate layer 13 consisting of a non-magnetic conductive material, a backing layer 14 consisting of a soft magnetic material and a magnetic recording layer 15 in which a magnetic domain is formed corresponding to a recorded magnetic signal are successively laminated on a substrate. The magnetic domain controlling layer 12 and the backing layer 14 are magnetically fixed through the intermediate layer 13. Thus, the generation of the domain wall displacement in the backing layer 14 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium having a magnetic recording layer in which magnetic domains are formed in accordance with a magnetic signal to be recorded, and more particularly to a magnetic recording medium suitable for use in a perpendicular magnetic recording system.

[0002]

2. Description of the Related Art Conventionally, a magnetic recording medium such as a magnetic disk or a magnetic tape has been used as a medium for recording image information and audio information used in various information processing apparatuses such as a computer apparatus. The magnetic recording medium includes a magnetic recording layer formed of a magnetic material, and a magnetic head of the recording / reproducing apparatus applies an external magnetic field that modulates according to a signal to be recorded. Is formed. Then, the direction of the magnetization in the magnetic domain formed in the magnetic recording layer is detected by the magnetic head, so that the recorded signal is reproduced.

[0003] In recent years, there has been a further demand for higher recording densities in the field of magnetic recording, and a perpendicular magnetic recording system has attracted attention as a technique satisfying such requirements. The perpendicular magnetic recording method is a recording method in which recording is performed by magnetizing in the thickness direction of the magnetic recording layer, unlike the longitudinal magnetic recording method in which recording is performed in the in-plane direction of the magnetic recording layer. In recent years, a technique of performing recording by a perpendicular magnetic recording method on a magnetic recording medium that has adopted a longitudinal magnetic recording method has attracted attention.

Accordingly, research and development on a so-called perpendicular double-layer film type magnetic recording medium aiming at improving the efficiency of a recording process as a magnetic recording medium compatible with such a perpendicular magnetic recording method has been advanced.

[0005] A perpendicular two-layer film type magnetic recording medium has a structure in which a magnetic recording layer made of a hard magnetic material and a backing layer made of a soft magnetic material are laminated. In a perpendicular double-layer film type magnetic recording medium, the backing layer has a function of concentrating the magnetic flux of the external magnetic field applied to the magnetic recording layer, thereby improving the recording efficiency.

[0006]

By the way, in a perpendicular double-layered magnetic recording medium having the above-mentioned structure, the magnetic domain wall moves in the backing layer made of a soft magnetic material. There was a problem that noise was generated. If spike noise is generated as described above, it becomes impossible to accurately detect a signal recorded at high density.

Accordingly, an object of the present invention is to provide a magnetic recording medium having good recording / reproducing characteristics corresponding to an increase in recording density by controlling the movement of a domain wall in a backing layer.

[0008]

According to the magnetic recording medium of the present invention, a magnetic domain control layer made of a Mn-based antiferromagnetic material, an intermediate layer made of a nonmagnetic conductive material, a soft magnetic material A backing layer made of a hard magnetic material, and a magnetic recording layer in which magnetic domains are formed according to a magnetic signal to be recorded are sequentially laminated, and the magnetic domain control layer and the backing layer are
It is characterized by being magnetically coupled via the intermediate layer.

In the magnetic recording medium according to the present invention configured as described above, the magnetic domain control layer and the backing layer are magnetically coupled via the intermediate layer. By controlling the magnetic coupling force generated between the layers, the movement of the domain wall generated in the backing layer can be suppressed. A desired strength of the magnetic coupling force between the magnetic domain control layer and the backing layer can be easily obtained by appropriately setting the thickness of the intermediate layer.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. Hereinafter, a magnetic disk 10 having a cross-sectional structure as shown in FIG. 1 will be described as one configuration example to which the present invention is applied. The magnetic disk 10 is a magnetic recording medium on which signals are recorded by forming magnetic domains magnetized in the thickness direction of the magnetic recording layer with respect to the magnetic recording layer. This is the magnetic recording medium employed.

As shown in FIG. 1, the magnetic disk 10 has a magnetic domain control layer 12 made of a Mn-based antiferromagnetic material, an intermediate layer 13 made of a nonmagnetic conductive material, and a
A backing layer made of a soft magnetic material and a magnetic recording layer made of a hard magnetic material are sequentially laminated.

The substrate 11 is formed, for example, of a metal material, a glass material, or a resin material into a substantially disk shape with a predetermined thickness. The diameter of the substrate 11 is, for example, 3.5 inches. In the magnetic disk 10, each layer is formed by being laminated on the main surface of a substrate 11, and this substrate 11 functions as a support, so to speak.

The magnetic domain control layer 12 is formed as a thin film on the substrate 11 using a Mn-based antiferromagnetic material. The magnetic domain control layer 12 is magnetically coupled to the backing layer 14 via the intermediate layer 13, and has a function of suppressing the movement of the domain wall generated in the backing layer 14. The magnetic domain control layer 12 is made of FeMn, IrMn, RhMn, PtMn, N
It can be formed of at least one kind of antiferromagnetic material selected from iMn, NiO or the like.

The intermediate layer 13 has a function of controlling a magnetic coupling force generated between the magnetic domain control layer 12 and the backing layer 14. For example, at least one selected from Cu, Au, Ag, and Ru is used. A thin film of a predetermined thickness is formed on the magnetic domain control layer 12 by a kind of non-magnetic conductive material.
In the magnetic disk 10, the magnetic coupling force generated between the magnetic domain control layer 12 and the backing layer 14 can be easily increased by appropriately selecting the material forming the intermediate layer 13 and the thickness of the intermediate layer 13. Can be controlled.

The backing layer 14 is formed of a soft magnetic material on the intermediate layer 13 and has a function of concentrating a magnetic flux of an external magnetic field applied to the magnetic recording layer 15 to magnetic domains. That is, in the magnetic disk 10, when an external magnetic field is applied in the thickness direction of the magnetic recording layer 15 (vertically) as shown by an arrow A in FIG. Through the backing layer 14 through
As shown by the arrow B in the middle, the magnetic flux flows in the in-plane direction in the backing layer 14. Therefore, the magnetic disk 10
Then, the magnetic flux is prevented from flowing in the in-plane direction in the magnetic recording layer 15, and the magnetic domains 15 a formed in the magnetic recording layer 15 are precisely magnetized in the thickness direction of the magnetic recording layer 15 as shown in FIG. Can be formed.

The magnetic recording layer 15 is formed on the backing layer 14 from a hard magnetic material in the form of a thin film. In the magnetic disk 10, a magnetic domain 15a is formed in the magnetic recording layer 15 according to a signal to be recorded.

The magnetic disk 10 constructed as described above
Since the magnetic domain control layer 12 and the backing layer 14 are magnetically coupled via the intermediate layer 13, it is possible to suppress the movement of the domain wall generated in the backing layer 14. Therefore, generation of spike noise in the reproduced signal can be prevented, and a signal recorded at high density can be detected with high accuracy.

The magnetic disk 10 can be formed by sequentially forming each layer on the substrate 11 by a thin film forming technique such as sputtering in the same manner as various magnetic disks widely used in the past.

The axis of easy magnetization of the backing layer 14 can be controlled by applying an external magnetic field during the formation of the backing layer 14, or by performing a heat treatment in a magnetic field after the formation. Is fixed in the direction of. At this time, for example, the backing layer 14 is formed at an appropriate temperature in a radial magnetic field, and is cooled after heating to provide a radial easy axis of magnetization on the disk-shaped substrate 11. desirable. When the backing layer 14 is subjected to a heat treatment in a magnetic field, the temperature is preferably set to 250 ° C.

Next, a recording / reproducing apparatus for recording / reproducing on / from the magnetic disk 10 will be described. In the following, as one configuration example of such a recording / reproducing apparatus, FIG.
The magnetic disk device 20 as shown in FIG.

As shown in FIG. 2, the magnetic disk drive 20 includes a chassis 2 provided inside a casing (not shown).
1, a spindle motor (not shown in FIG. 2) is provided, and a magnetic disk 10 is attached to a rotating shaft of the spindle motor so that a center axis thereof is aligned. The magnetic disk 10 is mounted on the chassis 21.
A head actuator 23 having a head slider 22 mounted on a magnetic head for recording and reproducing a magnetic signal is provided at the distal end.

In the chassis 21, a control circuit section 24 is provided on a surface opposite to the surface on which the magnetic disk 10 and the head actuator 22 are provided. The control circuit unit 24 includes a signal processing circuit that performs various kinds of signal processing and the like during recording and reproduction on the magnetic disk 10, a servo control circuit that performs servo control and the like of the magnetic head 22, a system controller circuit that controls the entire apparatus, and the like. Each circuit is realized by, for example, an electronic circuit configured by a semiconductor element or the like.

The magnetic disk 10 has a center hole 10a formed in a center portion having a substantially disk shape as a whole. The center hole 10a is fitted to a rotating shaft of a spindle motor and fixed by a clamper 25. In addition, the magnetic disk 10 controls the control circuit unit 24 when recording and reproducing magnetic signals.
In accordance with the rotation of the spindle motor, the driving of which is controlled at a predetermined speed in the direction of arrow C in FIG. The magnetic disk device 20 has a plurality of magnetic disks 10 mounted in this way.

The head actuator 23 includes a support arm 26 which is turned around a support shaft 25 and a voice coil motor 27 provided at one end of the support arm 26.
And a suspension 28 having a predetermined elasticity and extending from the other end, and a head slider 22 attached to the tip of the suspension 28.

The voice coil motor 27 is connected to the support arm 2
6 and the coil 27a
a and a magnet 27b attached to the chassis 21 at a position facing the a. And a magnetic field generated by supplying a current to the coil 27a;
Due to the magnetic action with the magnet 27b disposed opposite to the coil 27a, the support arm 26 is moved around the support shaft 25 in the direction of arrow D in FIG. Is rotatable by an angle of.

The suspension 28 has a head slider 22 attached to a tip end thereof. The head slider 22 is urged toward the main surface of the magnetic disk 10 by an elastic force while supporting the head slider 22.

The head slider 22 is mounted on the magnetic disk 10
An air lubrication surface (ABS surface) for generating a levitation force by an air flow generated by the rotation of the magnetic disk 10 is formed on the surface facing the magnetic disk 10. A magnetic head is mounted on the head slider 22 at the rear end side with respect to the traveling direction with respect to the magnetic disk 10.

In the magnetic disk drive 10 configured as described above, the head slider 22 is moved by the air flow generated by the rotation of the magnetic disk 10 to the magnetic disk 1.
The recording and reproduction with respect to the magnetic disk 10 are performed by the magnetic head mounted on the head slider 22 while flying at a predetermined flying height on the magnetic disk 10.

Next, a sample disk is prepared based on the magnetic disk 10 described above, and the magnetic coupling force acting between the magnetic domain control layer 12 and the backing layer 14 is changed by changing the thickness of the intermediate layer 13. That is, it is verified that the exchange coupling magnetic field can be changed.

First, a sample disk was prepared based on the magnetic disk 10. As this sample disk, Ta and NiFe were formed as a base layer with a thickness of 10 nm and 4 nm, respectively, on a silicon substrate corresponding to the substrate 11. The magnetic domain control layer 1 is formed on this underlayer.
IrMn is formed as a film having a thickness of 15 nm as an intermediate layer 1.
As No. 3, Cu was formed, and NiFe was formed as the backing layer 14 to a thickness of 5 nm. At this time, the film thickness of Cu corresponding to the intermediate layer 13 was 0 nm (corresponding to the case where the intermediate layer 13 was not formed), 0.5 nm, 1.0 nm, 1.
A plurality of sample disks were prepared at 5 nm and 2.0 nm. Each layer was formed by a sputtering method.

Next, the magnetization curve of each sample disk prepared as described above was measured at room temperature using a vibration sample type magnetization measuring device, and the magnetic domain control layer 12 and the backing layer 1 were measured.
4 was calculated. The result is shown in FIG.

As is clear from the results shown in FIG.
It can be seen that the exchange coupling magnetic field acting between the magnetic domain control layer 12 and the backing layer 14 greatly changes by changing the thickness of the intermediate layer 13. In FIG. 3, when the thickness of the intermediate layer 13 is 0 nm,
Exchange coupling magnetic field in the case where
[Oe], and the exchange coupling magnetic field when the thickness of the intermediate layer 13 was 2.0 nm was 3 [Oe].

Therefore, in the magnetic disk 10, it is apparent that the exchange coupling magnetic field acting between the magnetic domain control layer 12 and the backing layer 14 can be controlled by controlling the thickness of the intermediate layer 13. .

In the magnetic disk 10, the backing layer 1
4, the magnetization is saturated by an applied magnetic field of about several Oe,
By setting the thickness of the intermediate layer 13 to about 1 nm to 2 nm, the backing layer 14 can have a single magnetic domain structure, and the domain wall can be eliminated. Therefore, in the magnetic disk 10, spike noise can be prevented from being generated in the reproduction signal due to the movement of the domain wall, and the recording / reproduction characteristics can be improved.

The above results were obtained when NiFe was formed as the backing layer 14 to a thickness of 5 nm, but the material and the thickness of the intermediate layer 13 were not changed. May be appropriately selected according to the material and the thickness of the magnetic domain control layer 12 and the backing layer 14 so as to obtain an optimum exchange coupling magnetic field. Also in this case, as the magnetic domain control layer 12, a Mn-based antiferromagnetic layer having a relatively small thickness of about several nm to several tens of nm can be formed to make the backing layer 14 a single magnetic domain. .

In the above description, the case where the backing layer 14 is formed as a single layer has been described. However, the magnetic disk 10 may be formed by laminating the backing layer 14.

More specifically, as shown in FIG. 4, for example, as the backing layer 14, a first backing layer 20 and a second backing layer 21 each made of a soft magnetic material are used. Intermediate layer 2 formed of a magnetic conductive material
2 to form a stack. At this time, the first backing layer and the second backing layer are ferri-bonded by controlling the material and thickness of the intermediate layer 22.

In this case, since the first backing layer 20 and the second backing layer 21 are ferri-coupled to each other, the backing layer 14 has an effect of canceling each other's magnetic poles, thereby controlling the magnetic domains. Can be facilitated.

At this time, in the backing layer 14, the exchange coupling force controlled by the magnetic domain control layer 12 acts more remarkably on the first backing layer 20, and the magnetic coupling with the magnetic domain control layer 12 becomes stronger. I will. However, the first backing layer 20
The exchange coupling force between the magnetic layer 12 and the magnetic domain control layer 12 can be easily controlled by appropriately selecting the material and thickness of the intermediate layer 13.

Therefore, as shown in FIG. 4, when the backing layer 14 has a multilayer structure, the magnetic poles in the backing layer 14 can be canceled to easily control the magnetic domains. , The coupling force with the magnetic domain control layer 12 can be easily controlled. Therefore, by applying the present invention to the case where the backing layer 14 has a multilayer structure, it is easy to design the magnetic disk 10 more flexibly in accordance with desired magnetic characteristics.

In the above description, the magnetic disk 10 has been described as a magnetic recording medium employing a so-called perpendicular magnetic recording system, but the present invention is limited to application to a magnetic recording medium of the perpendicular magnetic recording system. However, the present invention can be applied to a magnetic recording medium of a longitudinal magnetic recording system, for example. Therefore, this case will be described below.

When the magnetic disk 10 is used as a longitudinal magnetic recording system, it is not particularly necessary to form the backing layer 14 below the magnetic recording layer 15. However, even in this case, as shown in FIG. 1, the magnetic recording layer 15 is formed thin, and the underlayer 1 is formed below the magnetic recording layer 15.
By forming 4, the magnetostatic energy can be reduced, and the free magnetic pole generated from the back side of the magnetic recording layer 15 can be short-circuited by the backing layer 14. Thus, when the recording density is increased, the stability of the magnetic domain can be improved. Therefore, it is desirable to provide the backing layer 14 even in the longitudinal magnetic recording system, especially when achieving a high recording density.

That is, even when the magnetic disk 10 is used as a longitudinal magnetic recording system, it is effective to reduce the thickness of the magnetic recording layer 15 and to provide the backing layer 14 in order to cope with a high recording density. At this time, the movement of the domain wall generated in the backing layer 14 becomes a problem as in the above description.

Therefore, in this case, by applying the present invention, the magnetic domain control layer 12 is provided, and the magnetic domain control layer 12 and the backing layer 14 are magnetically coupled to each other through the intermediate layer 13 so that the backing The movement of the domain wall generated in the layer 14 can be suppressed, and the recording / reproducing characteristics can be improved.

However, the effect provided by the backing layer 14 is slightly different between the perpendicular magnetic recording system and the longitudinal magnetic recording system.
That is, the backing layer 14 in the perpendicular magnetic recording system is
As an extension of the magnetic core in the magnetic head, a magnetic circuit is configured to improve recording efficiency, while
The backing layer 14 in the longitudinal magnetic recording method has an effect of short-circuiting leakage magnetic flux generated on the back surface side of the magnetic recording layer 15 to reduce magnetostatic energy and stabilize magnetic domains. In any case, it is desirable that the easy axis of the magnetic disk 10 be formed radially from the center of the disk.

The present invention is not limited to the application to a magnetic disk, but it goes without saying that the invention can be widely applied to various magnetic recording media such as a magnetic tape and a magnetic card.

[0047]

According to the magnetic recording medium of the present invention, since the magnetic domain control layer and the backing layer are magnetically coupled via the intermediate layer, a magnetic field generated between the magnetic domain control layer and the backing layer is provided. By controlling the dynamic coupling force, it is possible to suppress the movement of the domain wall generated in the backing layer. Therefore,
The magnetic recording medium according to the present invention can prevent spike noise from being generated in a reproduction signal, and can be used even when magnetic domains are formed at a high density corresponding to a high recording density. This makes it possible to ensure excellent recording and reproduction characteristics.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part showing a sectional structure of a magnetic disk shown as one configuration example to which the present invention is applied.

FIG. 2 is a schematic configuration diagram of a magnetic disk device shown as an example of a configuration of a recording and reproducing device that performs recording and reproduction on the magnetic disk.

FIG. 3 is a diagram showing an exchange coupling magnetic field acting between a magnetic domain control layer and a backing layer obtained when the thickness of an intermediate layer is changed in a sample disk prepared based on the magnetic disk.

FIG. 4 is a view showing a modification of the magnetic disk, and is a cross-sectional view showing an example in which a backing layer has a laminated structure.

[Explanation of symbols]

10 magnetic disk, 11 substrate, 12 magnetic domain control layer,
13 intermediate layer, 14 underlayer, 15 magnetic recording layer, 15
a magnetic domain

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Junichi Sugawara 6-35 Kita Shinagawa, Shinagawa-ku, Tokyo F-term in Sony Corporation (reference) 5D006 BB07 CA01 CA03 CA03 CA05 CA06

Claims (5)

[Claims] A magnetic domain control layer made of a Mn-based antiferromagnetic material, an intermediate layer made of a nonmagnetic conductive material, a backing layer made of a soft magnetic material, and a hard magnetic material, And a magnetic recording layer in which magnetic domains are formed in accordance with a magnetic signal to be formed is sequentially laminated, and the magnetic domain control layer and the backing layer are magnetically coupled via the intermediate layer. Magnetic recording medium. 2. The magnetic recording medium according to claim 1, wherein a magnetic signal is recorded on the magnetic recording layer with a direction of magnetization in the magnetic domain being a thickness direction of the magnetic recording layer. 3. The magnetic domain control layer is made of FeMn, IrM.
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is made of at least one antiferromagnetic material selected from n, RhMn, PtMn, NiMn, and NiO. 4. The magnetic recording medium according to claim 1, wherein the intermediate layer is formed of at least one non-magnetic conductive material selected from Cu, Au, Ag, and Ru. 5. The backing layer comprises a first backing layer and a second backing layer.
And a backing layer formed of a nonmagnetic conductive material.
2. The magnetic recording medium according to claim 1, wherein the first backing layer and the second backing layer are ferri-bonded with each other with an intermediate layer interposed therebetween.