JPH0341881B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a perpendicular thermal (optical) magnetic recording method in which information is written using the Curie point or compensation point of a perpendicular magnetic recording medium.

Conventionally, in magnetic recording, in order to improve the magnetic recording density, it is essential to reduce the size of the magnetically recorded bit patterns, but if the interval λ of the bit patterns is reduced, the There is a law that states that the distance δ between the magnetic head and the magnetic recording medium must be made small. This is because the magnetic field lines of a small magnet extend farther in proportion to the size of the magnet. Therefore, the following equation holds between the interval λ between the bit patterns, the interval δ between the magnetic head and the magnetic recording medium, and the level D (decibel) of the read output electrical signal of the magnetic head.

D≒-55δ/λ (decibel: dB) ...(1) As can be seen from this equation (1), the level D of the read output electrical signal is determined when the distance δ between the magnetic head and the magnetic recording medium is zero (the magnetic head is When the output electrical signal is in close contact with the magnetic recording medium), the interval δ
When the value of is A, it is reduced by some decibels from that value. For example, when the bit pattern spacing λ is 1 μm, the value of the spacing δ between the magnetic head and the magnetic recording medium is
Even if it were 0.4 μm, the value of this reduction would be 22 decibels, which would reduce the output voltage by about 1/10. Therefore, in order not to reduce the output voltage of the magnetic head, the value of δ/λ must be maintained at about 0.2 to 0.4.

FIG. 1 is a diagram showing the configuration of a conventional perpendicular magnetic recording head based on the above principle.
-Cr film, MnBi film, Tb-Fe film, Gd-Fe film,
This is a magnetic head for performing perpendicular magnetic recording and reproduction of information on a perpendicular magnetic recording medium M in which a rare earth-transition metal based amorphous magnetic thin film such as a Dy-Fe film is formed on a substrate by vapor deposition, sputtering, etc. This magnetic head consists of a main magnetic pole 3 having a permalloy strip 1 surrounded by a protective material 2 such as plastic material.
An auxiliary magnetic pole 5 is provided in which a coil 4 is provided on a high magnetic permeability ferrite material that faces the main magnetic pole 3 with the perpendicular magnetic recording medium M interposed therebetween.

Figure 2 shows the conventional perpendicular thermo-(optical) magnetic recording method (also called magneto-optical recording method as it uses a laser beam etc. as a heating means) for high-density magnetic recording, similar to the one in Figure 1. This is an explanatory diagram, in which a laser beam from a recording laser device 6 is applied to the perpendicular magnetic recording medium M according to information.
The perpendicular magnetic recording medium M is condensed and irradiated with a condensing lens 7 to raise the temperature of the perpendicular magnetic recording medium M to the Curie point to lower its holding force, and the external magnetic field from the coil 8 reverses the magnetic moment in the direction of the magnetic field. This is a method of recording information using

The conventional high-density magnetic recording method using the magnetic head shown in FIG. 1 has problems such as maintaining a gap between the perpendicular magnetic recording medium M and the magnetic head and wearing out the contact portion.

Furthermore, in the perpendicular thermomagnetic recording method shown in FIG. 2,
Because it cannot be made smaller than the wavelength of the heat ray due to the diffraction phenomenon of the spot of the heat ray such as a laser beam,
There were also limits to high-density magnetic recording.

Therefore, the inventors of the present invention continuously heated a minute portion on a perpendicular magnetic recording medium to a temperature higher than the Curie point, moved the heated minute portion, and when the temperature reached the vicinity of the Curie point, applied Perpendicular heat (light) that magnetizes in the direction of the magnetic field and retains its magnetization when the temperature further decreases, making perpendicular magnetic recording possible with dimensions smaller than the dimensions of the heated minute portion.
A magnetic recording method was developed and proposed.

FIG. 3 is a diagram showing an example of an apparatus for carrying out the perpendicular thermal (optical) magnetic recording method. In the figure, 11 is a heat ray source such as a semiconductor loser,
It emits light continuously. 12 is a lens system that focuses heat rays such as laser light emitted from this heat ray source 11, and 13 is a perpendicular magnetic recording medium that is magnetized only in the direction perpendicular to its film surface (perpendicular magnetic anisotropy); It is arranged to allow high-speed movement.
14 is a coil for controlling the bias magnetic field, and 15 is a signal source for causing a current corresponding to information to flow through the coil 14.

The perpendicular magnetic recording medium 13 preferably has a low Curie point Tc (at least 70°C), and is made of a thin film of MnBi, heavy rare earth-transition metals such as Tb-Fe, Gd-Fe,
It is composed of amorphous thin films such as Dy-Fe, Gd-Co, and Ho-Co. Moreover, the coercive force Hc rapidly decreases from slightly below the Curie point Tc.

FIG. 4 is an enlarged view of the position P on the perpendicular magnetic recording medium 13 shown in FIG.
3 indicates point P before movement, and the solid circle circle indicates point P after movement.

Next, the operation of this implementation device will be explained.

Assuming that the perpendicular magnetic recording medium 13 is moving at a high speed in the direction of the arrow, the moving distance of point P in the direction of the arrow is x, and heat rays are being irradiated from the heat ray source 11, after Δt seconds, The part of the hot ray spot (the part heated above the Curie point) indicated by the dotted circle A in FIG. 4 moves by Δx in the direction of the arrow, and comes to the position indicated by the solid circle B. Therefore, the shaded portion C is no longer heated by the heat ray irradiation, and its temperature decreases to below the Curie point. Here, as shown in FIG. 3, the magnetic field caused by the current flowing through the coil 14 is also applied to the shaded part C of the perpendicular magnetic recording medium 13, so that the temperature drops from the Curie point to room temperature. The hatched portion C once passes through a state where the coercive force Hc is extremely low near the Curie point, and is magnetized in the direction of the magnetic field received from the coil 14 at this time. Since the coercive force Hc of the perpendicular magnetic recording medium 13 increases rapidly as it moves away from the Curie point and approaches room temperature, the magnetization direction of the shaded portion C will be reversed even if the magnetic field from the coil 14 is subsequently reversed. It is retained without doing anything.

In this way, as shown in FIG. 5A, a crescent-shaped magnetized magnetic recording pattern is sequentially formed on the perpendicular magnetic recording medium 13. The magnetization of the shaded portion C in FIG. 5A is directed toward the front of the paper, and the magnetization of the non-hatched portion is directed toward the back. This magnetization state is set at the center of the recording track (x
When shown along the axis (on the axis), it becomes as shown in FIG. 5B.

It will be understood from the above description that the crescent-shaped magnetic recording pattern is much finer than the diameter of the hot ray spot.

However, in such a vertical thermal (optical) magnetic recording method, information is recorded in a crescent-shaped magnetic pattern, as shown in FIGS. 4 and 5A. As shown in Figure 6, the contours are jagged and deformed crescent-shaped magnetic patterns, and when such magnetic patterns are arranged in high density, the part between each magnetic pattern overlaps with the adjacent crescent-shaped magnetic pattern. There were some parts that came into contact with or overlapped with each other, resulting in bit errors.

It has been found that the cause of the deformed crescent-shaped magnetic pattern is that thermal diffusion occurs on the perpendicular magnetic recording medium before it is heated above the Curie point and written near the Curie point.

The present invention has been made to eliminate the above-mentioned drawbacks, and its features include continuously heating a minute portion on a perpendicular magnetic recording medium to a temperature higher than the Curie point, and cooling the heated minute portion. The purpose is to cool the microscopic portion rapidly, and when the temperature of this minute portion reaches near the Curie point, apply a write magnetic field to magnetize it in the direction of this magnetic field, and then maintain the magnetization by lowering the temperature.

Hereinafter, the present invention will be explained in detail with reference to Examples.

In FIG. 7, parts having the same functions as those in FIG. 3 are given the same symbols.

FIG. 7 is a diagram showing the configuration of an apparatus for implementing the perpendicular thermomagnetic recording method of the present invention. In the figure, 11 to 15
is the same as that in FIG. 3, so its explanation will be omitted here. 16 is a nozzle for forcibly cooling a heated minute portion of the perpendicular magnetic recording medium 13 to shorten the heat diffusion time; 17 is a nozzle 16;
18 is an air tank to which the hose 17 is connected, and this air tank 18
is filled with compressed air.

Next, the operation of this embodiment will be explained.

The operation of applying a write magnetism by irradiating a minute portion of the perpendicular magnetic recording medium 13 with a hot ray such as a laser beam is the same as that shown in FIG. 3, and therefore will not be described here.

After the perpendicular magnetic recording medium 13 is heated by heat ray irradiation, when the temperature decreases to around the Curie point, a portion of the surface of the perpendicular magnetic recording medium 13 heated by the heat ray spot irradiation is heated. Compressed air is blown from the air tank 18 through the hose 17 and nozzle 16, and when the perpendicular magnetic recording medium 13 is removed from the hot ray spot, its temperature drops rapidly, the heat diffusion time becomes shorter, and the magnetic pattern is deformed. recorded without being recorded.

In this embodiment, a method using compressed air and a nozzle is used as the forced cooling means, but it goes without saying that other known forced cooling methods may be used.

As explained above, according to the present invention, a perpendicular magnetic recording medium is heated and then forcibly cooled to shorten the time for thermal diffusion, so that a uniform crescent-shaped magnetic pattern can be obtained. As a result, even if the magnetic patterns are arranged at high density, there is no risk of the magnetic patterns coming into contact or overlapping each other, and bit errors can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a conventional perpendicular magnetic recording head, FIG. 2 is a diagram for explaining a conventional perpendicular thermomagnetic recording method, and FIG. 3 is a diagram showing a perpendicular thermomagnetic recording method according to the present invention. FIG. 4 is an enlarged view of point P, which is irradiated with the hot ray spot on the perpendicular magnetic recording medium shown in FIG. 3, and FIG. 6 is a detailed diagram of the magnetic recording state shown in FIG. 5, and FIG. 7 is a diagram showing the configuration of an apparatus for implementing the perpendicular thermomagnetic recording method of the present invention. It is a diagram. 11... Heat ray source, 12... Condensing lens system, 13
... Vertical thermomagnetic recording medium, 14 ... Coil, 15
...Signal source, 16...Nozzle, 17...Hose,
18...Air tank.

Claims (1)

[Claims] 1. Continuously heating a minute part on a perpendicular magnetic recording medium to a temperature higher than the Curie point temperature, and applying a magnetic field perpendicular to the recording surface of the perpendicular magnetic recording medium to an area wider than the heated minute part. , the vicinity of the heated microscopic part was forcibly cooled, and then the heated microscopic part was moved, and when its temperature reached the vicinity of the Kyrie point, it became magnetized in the direction of the applied magnetic field, and the temperature further decreased. At the same time, it retains its magnetization,
A perpendicular thermal (optical) magnetic recording method, characterized in that perpendicular magnetic information of a size smaller than the size of the heated minute portion is recorded.