JPH1097714A - Magnetic disk and magnetic disk device using the same - Google Patents

Abstract

(57) [Problem] To provide a magnetic disk suitable for high-density recording and a magnetic disk device with high recording density. SOLUTION: This magnetic disk includes a base 1, an underlayer 2 formed on the base 1, a recording layer 3 formed on the underlayer 2, and a protective film 4 formed on the recording layer 3. The recording layer has a two-layer structure of a plurality of magnetic bodies 5 and 6 having different fluctuation fields. According to the present invention, different information can be recorded on the surface layer side and the deep layer side of the recording layer, and high surface recording density can be achieved. Therefore, a magnetic disk device with a high recording density can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk and a magnetic disk drive using the magnetic disk, and more particularly to a magnetic disk having a thin film structure suitable for high recording density and a magnetic disk drive using the same.

[0002]

2. Description of the Related Art Conventionally, as this kind of magnetic disk,
2. Description of the Related Art A thin-film magnetic disk as shown in FIG. 2 is known. FIG. 2 is a sectional view showing a conventional example of a magnetic disk. In the figure, reference numeral 21 denotes a magnetic disk, and this magnetic disk 21 is formed, for example, on a substrate 1 made of Al.
r underlayer 2 made of, for example, CoC
It has a recording layer 3 made of r, and has a protective film 4 made of, for example, C on the recording layer 3. The magnetic disk having the above configuration is described in, for example,
No. 022617. In addition, the magnetic disk having the above-described configuration includes, for example, the first international conference on perpendicular magnetic recording, p. 36 (1989), instead of recording different information between the surface layer and the deep layer of the recording layer, one bit information is recorded from the surface layer to the deep layer.

In order to achieve a high recording density by using the conventional magnetic disk having such a configuration, it is necessary to reduce noise in order to secure S / N in response to a reduction in bit area. Instead, it is necessary to isolate and refine crystal grains in the magnetic film.

However, when the magnetic particles are miniaturized, the influence of the thermal fluctuation on the magnetic characteristics increases, and the magnetization reversal due to the thermal fluctuation tends to occur as the temperature increases or the magnetic field application time increases. As a result, the magnetization changes with the magnetic field application time, and the longer the magnetic field application time, the smaller the value of the magnetic field (coercive force) at which the magnetization becomes zero.
For example, when the magnetic field application time is 1 second (corresponding to the magnetic field application time when measuring with a sample vibrating magnetometer) (hereinafter referred to as the measured coercive force Hc), the magnetic field application time is 10 minutes.
In the case of nanosecond (corresponding to the recording magnetic field application time in the magnetic disk device), the former has a smaller value than the latter (hereinafter referred to as the recording coercive force H0).

FIG. 3 shows a characteristic diagram a of an example of the dependence of the coercive force on the applied magnetic field when the fluctuation field is small. A characteristic diagram b of an example of the dependence of the coercive force on the applied magnetic field when the fluctuation field is large is also shown. When the fluctuation field is small, the recording coercive force H0 is substantially equal to the measured coercive force Hc,
When the fluctuation field increases, the recording coercive force H0 becomes the measured coercive force H
significantly larger than c. This phenomenon has been known for a long time and is called magnetic viscosity. Regarding magnetic viscosity, for example, I-E-I-E-Transaction On
Magnetics MDG 20 pp754
(1984). According to IEICE technical report M-AR 95-13 (1995), it is evident that a medium having a larger fluctuation field indicating the magnitude of thermal fluctuation has a smaller magnetization reversal unit and a smaller medium noise. Have been.

However, when the fluctuation field increases with the noise reduction of the medium, the effect of the magnetic viscosity becomes remarkable. Therefore, as described above, the storage corresponding to the magnetic field application time when measuring with the sample vibrating magnetometer is used. The magnetic force (measured coercive force Hc) is significantly smaller than the coercive force (recording coercive force H0) corresponding to the recording magnetic field application time in the magnetic disk drive. Since it is necessary to increase the measured coercive force Hc in order to form and maintain the high-density recording magnetization, when the fluctuation field is large, the recording coercive force Hc is increased.
0 becomes extremely large, and saturation recording with a magnetic head becomes difficult.

Therefore, there is a limit in increasing the recording density in the conventional recording method for recording 1-bit information from the surface layer to the deep layer.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic disk suitable for high-density recording and a magnetic disk device with high recording density, which solves the problems of the prior art.

[0009]

In order to achieve the above object, a magnetic disk according to the present invention comprises: a base layer formed on a substrate; a recording layer formed on the base layer; A magnetic disk having at least a protective film formed thereon, wherein the recording layer is formed of a laminated film in which a plurality of magnetic materials having different fluctuation fields are laminated, and the magnetic characteristics and recording conditions of the laminated film are optimized. Thus, different information can be recorded on the surface layer side and the deep layer side of the recording layer. That is, in the embodiment shown in FIG. 1, the substrate 1, the underlayer 2 formed on the substrate 1, the recording layer 3 formed on the underlayer 2, and the recording layer 3 formed on the recording layer 3 In the magnetic disk having at least the protective film 4, the recording layer 3 has a laminated structure having a magnetic field 5 adjacent to the underlayer 2 and having a high fluctuation field and a magnetic substance 6 adjacent to the protective film 4 and having a low fluctuation field. It is characterized by being composed of a film.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a magnetic disk and a magnetic disk device according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view schematically showing one embodiment of a magnetic disk according to the present invention. In FIG. 1, reference numeral 20 denotes a magnetic disk, which is a base 1, an underlayer 2 formed on the base 1, a recording layer 3 formed on the underlayer 2, and a protection layer formed on the recording layer 3. And a membrane 4.

The difference between this embodiment and the structure of the conventional example shown in FIG. 3 is that the recording layer 3 is not a single layer as in the conventional example,
It has a two-layer structure of a magnetic body 5 and a magnetic body 6 having different fluctuation fields, and records different information between the magnetic body 5 and the magnetic body 6. That is, the recording layer 3 is composed of a laminated film in which a plurality of magnetic materials having different fluctuation fields are laminated, and the magnetic material 5 in a portion adjacent to the underlayer 2 has a fluctuation field larger than other portions in the magnetic material 3. In this case, different information is recorded on the magnetic body 5 and the magnetic body 6 using a material having a high density. The recording layer material may be CoCr, CoCr.
Any of magnetic thin films such as Ta, CoCrPt, and CoCrPtTa may be used.

Such a magnetic disk is manufactured, for example, as follows. First, a 1 mm-thick plate made of Al is used as the base 1, and C
An r film is deposited by sputtering to a thickness of 30 nm, then a Co66Cr22Pt12 film to be a magnetic material 5 is deposited to a thickness of 20 nm by a sputtering method, and then Co78 to be a magnetic material 6
Cr16Ta6 is deposited to a thickness of 20 nm by a sputtering method, and C serving as a protective film 4 is deposited to a thickness of 5 nm by a sputtering method.
Deposit thickness. In this embodiment, the fluctuation field of the magnetic body 5 is 4
The fluctuation field of the magnetic body 6 is 0 Oersted and 5 Oersted. The coercive force (measured coercive force) of the medium measured by the sample vibration type magnetometer is about 2000 for both the magnetic material 5 and the magnetic material 6.
Oersted. As for the plurality of magnetic materials constituting the recording layer 3 having different fluctuation fields as in this embodiment, it is desirable that the magnetic material 5 having a high fluctuation field has a fluctuation field at least four times the fluctuation field of the magnetic material 6. .

Here, an example of a magnetic disk drive on which the magnetic disk of this embodiment is mounted will be described with reference to FIG. 4A and 4B are schematic configuration diagrams of one embodiment of a magnetic disk drive according to the present invention, in which FIG. 4A is a plan view, and FIG. 4B is a cross-sectional view taken along line AA ′ in the plan view. . In FIG. 2, reference numeral 20 denotes a magnetic disk, for example, a magnetic disk of a Co-based sputtering medium, 9 denotes a spindle motor for rotating and driving the magnetic disk 20, and 7 denotes a magnetic head for recording and reproducing signals on the magnetic disk. Reference numeral 8 denotes a so-called rotary actuator for moving the magnetic head 7 in the radial direction on the magnetic disk. Reference numeral 10 denotes a recording / reproducing signal processing system for processing recording / reproducing signals of the magnetic head, and a magnetic head. Head 7 and magnetic disk 20
Is a signal processing section comprising a control signal processing system for controlling the driving of the control signal. A plurality of magnetic disks are mounted on a spindle motor 9, and a magnetic head 7 is provided on each of the magnetic disks.

In the magnetic disk drive, the reproduced waveform signal is processed by the PRML method, and the magnetic head 7 is positioned by the servo track positioning method. The rotation speed of the spindle motor is 7,200 rpm. As the magnetic head 7, a self-induction type head was used for recording, and a magnetoresistive head was used for reproduction. The track width and gap length of the recording head are 1.3 microns and 0.4 microns, respectively. The track width and gap length of the read head are 1.1 microns and 0.2 microns, respectively. The areal recording density is 5 gigabits per square inch.

FIG. 5 and FIG. 6 schematically show a recording process when the present embodiment is carried out.

FIG. 5 schematically shows a recording process when new information is recorded only on the magnetic material 6 on the surface layer side.
FIG. 3 is a sectional view of a medium. It is assumed that the recording magnetization as shown in FIG. 5A is formed on an arbitrary track of the magnetic disk 20, and when new information is to be recorded only on the surface-side magnetic body 6 in FIG. As shown in (b), recording is performed on the magnetic body 6 with a head magnetic field that does not erase the magnetization of the magnetic body 5 on the deep layer side. As a result, a recording magnetization state as shown in FIG. 5C is formed.

On the other hand, FIG. 6 is a cross-sectional view of a head / medium schematically showing a recording process when new information is recorded only on the deep magnetic material 5. If new information is to be recorded only on the magnetic material 5, the magnetic material 6 on the surface layer must be
The information already recorded on the same track portion of the above is reproduced by the reproducing head, and once stored in the cache memory,
As shown in FIG. 6B, recording is performed on the deep magnetic layer 5. At this time, as shown in FIG. 6C, magnetization similar to that of the magnetic body 5 is also formed on the magnetic body 6 on the surface layer side. Next, as shown in FIG. 6D, the information temporarily stored in the cache memory is recorded again on the magnetic body 6 with a head magnetic field that does not erase the magnetization of the deep magnetic body 5. Thereby, different information can be recorded in the magnetic body 5 and the magnetic body 6.

The magnetic disk 20 of this embodiment is the same as the magnetic disk drive shown in FIG.
When used in place of the above, the recording density per unit area of the magnetic disk (area recording density) is twice as large as that of the conventional example. Therefore, the magnetic disk 20 having the structure of the present embodiment
Was suitable for increasing the areal recording density.

In order to facilitate control of the film structure and magnetic characteristics of the magnetic material 5 and the magnetic material 6, a 3 nm thick Ti
Even with a magnetic disk (not shown) having a structure in which an intermediate layer made of Cr was provided, it was possible to achieve the same areal recording density as the magnetic disk shown in the figure.

[0021]

As is clear from the above embodiments, according to the present invention, a high linear recording density can be achieved without significantly increasing noise and recording current. Therefore, a magnetic disk device with a high recording density can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a magnetic disk according to the present invention.

FIG. 2 is a sectional view showing an example of a conventional magnetic disk.

FIG. 3 is a characteristic diagram showing an example of the dependence of a coercive force on an applied magnetic field, wherein a characteristic diagram a is an example when the fluctuation field is small, and a characteristic graph b is an example when the fluctuation field is large.

FIGS. 4A and 4B are schematic diagrams showing one embodiment of a magnetic disk drive provided with a magnetic disk according to the present invention, wherein FIG. 4A is a plan view, and FIG. FIG.

FIG. 5 is a cross-sectional view of a head / medium schematically showing a recording process in a magnetic disk device having a magnetic disk according to an embodiment of the present invention.

FIG. 6 is a cross-sectional view of a head / medium schematically showing a recording process in a magnetic disk device having a magnetic disk according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Underlayer, 3 ... Recording layer, 4 ... Protective film, 5 ...
High fluctuation field magnetic material, 6 low fluctuation field magnetic material, 7 magnetic head, 8 magnetic head drive unit, 9 magnetic disk drive unit, 10 signal processing unit, 20 magnetic disk, 21 magnetic disk.

Claims (7)

[Claims] In a magnetic disk having at least a base layer formed on a substrate, a recording layer formed on the base layer, and a protective film formed on the recording layer, the recording layer has fluctuations. A magnetic disk comprising a laminated film in which a plurality of magnetic materials having different fields are laminated. 2. A method according to claim 1, wherein a fluctuation field of a magnetic substance adjacent to said protective film is set to be lower than a fluctuation field of another magnetic substance part in said recording layer. 2. The magnetic disk according to claim 1, wherein the magnetic disk is formed. 3. A method according to claim 1, wherein, of the plurality of magnetic materials constituting the recording layer, different information is recorded in a magnetic material portion adjacent to the protective film and in another magnetic material portion in the recording layer. 3. The magnetic disk according to claim 1, wherein: 4. A magnetic disk having at least a base layer formed on a substrate, a recording layer formed on the base layer, and a protective film formed on the recording layer, wherein the recording layer fluctuates. What is claimed is: 1. A magnetic disk, comprising: a laminated film in which a plurality of magnetic materials having different fields are laminated, wherein a non-magnetic material is laminated between respective magnetic materials constituting a recording layer. 5. A magnetic field adjacent to the protective film among a plurality of magnetic materials constituting the recording layer, wherein a fluctuation field of the magnetic material is set lower than a fluctuation field of another magnetic material portion in the recording layer. The magnetic disk according to claim 4, wherein the magnetic disk is formed. 6. A method according to claim 1, wherein, of a plurality of magnetic materials constituting said recording layer, different information is recorded in a magnetic material portion adjacent to said protective film and in another magnetic material portion in said recording layer. 6. The magnetic disk according to claim 4, wherein: 7. A magnetic disk drive unit for rotating at least one magnetic disk according to any one of claims 1 to 6, and recording / reproducing on / from the magnetic disk. A magnetic head, a magnetic head drive unit for driving the magnetic head in a radial direction on the magnetic disk, and a magnetic disk drive unit for processing a recording signal to the magnetic head and a reproduction signal from the magnetic head; A magnetic disk drive having a signal processing system for processing a control signal of a head drive unit.