JPH03296938A - Magneto-optical recording medium and recording method - Google Patents

Abstract

PURPOSE:To obtain a medium for direct overwriting with large reproducing output by depositing a first magnetic layer and a second magnetic layer on a substrate in a manner that the layer 2 satisfies a specified condition. CONSTITUTION:On a substrate 2, the first magnetic layer 3 having perpendicular magnetic anisotropy and comprising rare earth-transition metal amorphous alloy and the second magnetic layer 4 comprising rare earth-transition metal amorphous alloy coupled with the layer 3 by exchange force are formed so as to satisfy the relations expressed by formulae I and II. In the formulae, Tc1 is the Curie temp. of the first magnetic layer 3, Tc2 is the Curie temp. of the second magnetic layer 4, Hc1 is the coercive force of the first magnetic layer 3, Hc2 is the coercive force of the second magnetic layer 4, Hw1(2) is the exchange force from the second magnetic layer 4 to the first magnetic layer 3, Hw2(1) is the exchange force from the first magnetic layer 3 to the second magnetic layer 4, Hini is the initial auxiliary magnetic field, and Hb is the recording magnetic field. Thus, the obtd. magneto-optical recording medi um has large reproducing output and can be used for direct overwriting.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magneto-optical recording medium and a recording method, and more specifically, to a magneto-optical recording medium that can be directly overridden and a magneto-optical recording medium using this magneto-optical recording medium. This relates to magnetic recording methods.

[Prior Art] FIG. 3(a) is a sectional view of a main part of a conventional magneto-optical recording medium and a recording device disclosed in, for example, Japanese Patent Application Laid-open No. 63-285740. Recording medium, (2
) is a transparent substrate, (3) is a first magnetic layer, and (4) is a second magnetic layer.
The magnetic layer is made of a ferrimagnetic material such as TbFe or TbFeCo. (7) is a laser beam for recording, erasing, and reproducing, and (8) is a single external magnet.

The magneto-optical recording medium (1) includes a substrate (2) and a first magnetic layer (3).
and a second magnetic layer (4), and a first magnetic layer (3).
An exchange force acts between the magnetic layer and the second magnetic layer (4), and the first magnetic layer (3) is a recording layer for retaining information.

The second magnetic layer (4) is made of a rare earth-transition metal magnetic material having a compensation temperature between room temperature and the Curie temperature.

FIG. 3(b) is a hysteresis characteristic diagram of the second magnetic layer (4) at room temperature, and the sublattice magnetization direction of the second magnetic layer (4) is in the sublattice magnetization direction of the first magnetic layer (3). Figure 3 (e
) is a characteristic diagram of the generated magnetic field of the external magnet (8), where the single external magnet (8) has a generated magnetic field distribution in a fixed direction toward the recording medium (1), and has a generated magnetic field distribution at the end directly below the laser beam (7). Hb,
A magnetic field called old ni is generated at the other end. Hini is the second magnetic layer (4) regardless of the magnetization direction of the first magnetic layer (3).
) and the second magnetic layer (4) maintains its magnetization direction immediately above the single external magnet (8). The magnetization direction of the first magnetic layer (3) changes only with the intensity of the laser beam (A) during recording and erasing.

For example, the first magnetic layer (3) uses a magnetic material in which the transition metal magnetic moment is dominant at room temperature. The exchange force works to align the sublattice magnetic moments of each magnetic layer, and the magnetization direction is the sum of the transition metal magnetic moment and the rare earth metal magnetic moment, which are in opposite directions, so below the compensation point of the second magnetic layer (4), The magnetization of each magnetic layer is stable in the direction in which they face each other, and the direction in which the magnetization in each magnetic layer is aligned is stable above the compensation point of the second magnetic layer (4).

Increase the output of the laser beam (7) to remove the first magnetic layer (3)
is aligned with the magnetization direction of the second magnetic layer (4) due to the exchange force, and when the sublattice magnetization direction of the second magnetic layer (4) is not changed by Hb, the magnetization direction of the second magnetic layer (4) is aligned with the first magnetic layer. Layer (3
) is transcribed. At this time, the second magnetic layer (4) is directed upward (
Since the transition metal magnetic moment is initialized in a downward direction), the magnetization direction of the first magnetic layer (3) is downward (the transition metal magnetic moment is downward), and the second magnetic layer (4) is initialized so that the transition metal magnetic moment is directed downward.
), the compensation temperature of the second magnetic layer (4) is also exceeded, and the magnetization direction of the second magnetic layer (4) is directed upward due to Hb (the transition metal magnetic moment is directed upward). The magnetization direction of the second magnetic layer (4) is the same as that of the first magnetic layer (3).
), and the magnetization direction of the first magnetic layer (3) is directed upward (
By changing the magnetization state of the first magnetic layer (3) simply by changing the output of the laser beam (7) in this way, the transition metal magnetic moment becomes upward)? ! ! Overrides are possible.

[Problems to be Solved by the Invention] Conventional magneto-optical recording media and recording systems are configured as described above and can be directly overridden, but it has been discovered that the same operation is possible even if the configuration of the magnetic layer is different. .

Further, the Curie temperature of the first magnetic layer serving as the reproduction layer is lower than the Curie temperature of the second magnetic layer, and if the laser power applied during recording is not increased, the reproduction output cannot be increased.

Furthermore, as shown in JP-A-1-100752, the Curie temperature of the first magnetic layer is higher than that of the second magnetic layer, and even if a recording medium with a small coercive force at room temperature is used, the magnetic field can be applied at high speed. Direct overrides are not possible without modulating .

This invention was made to solve the above-mentioned problems, and has a large playback output, and it can directly override by changing the output output of a single laser beam in an environment where a steady magnetic field is generated during recording. The purpose of the present invention is to obtain a magneto-optical recording medium and a recording method that can perform the following steps.

[Means for Solving the Problems] A magneto-optical recording medium according to the present invention includes: a first magnetic layer made of a rare earth-transition metal amorphous alloy having perpendicular magnetic anisotropy provided on a substrate; The first magnetic layer is provided in the magnetic layer.
A second magnetic layer made of a rare earth-transition metal amorphous alloy is bonded to the magnetic layer by exchange force, and Tc+ > Tc, where Tc: Curie temperature Tc of the first magnetic layer.
2: Satisfies the Curie temperature of the second magnetic layer, and at room temperature Hc, -Hvv,, +> I Hini I > HC
ltHWl+21> Hb Hc + HW 11
21 > 0 However, Hc: Coercive force of the first magnetic layer HC2: Coercive force of the second magnetic layer Hw + + 21: Exchange force HVV received by the first magnetic layer from the second magnetic layer 2111: Coercive force of the second magnetic layer Exchange force received from the first magnetic layer (old ni): initial auxiliary magnetic field Hb: satisfies the recording magnetic field.

Further, the magneto-optical recording method according to the present invention (a) uses the above magneto-optical recording medium, (b) moves the W light distribution magnetic recording medium in a fixed direction, and (e) erases and erases the intensity of the laser beam. (d) The applied magnetic field is in a constant direction and the magnetic field strength is different between the area immediately before the laser beam is irradiated and the area where the laser beam is irradiated; (e) Recording. Hr after operation and before playback operation
>Hc+-Hwzt+Hb-Hr<0 A reproduction auxiliary magnetic field Hr is applied to the medium.

[Function] In the magneto-optical recording medium of the present invention, when the auxiliary first magnetic layer HC+<Hwl, after overriding, Hw,
-Hc+ or higher magnetic field is applied to the second recording layer.
Transferring the information of the magnetic layer to the first magnetic layer and reproducing it, Hc;
>Hw+, override is possible with an external magnet, and since the sublattice magnetizations of both magnetic layers are aligned after recording, reproduction can be performed as is.

In addition, in the magneto-optical recording method of the present invention, since the coercive force is larger at room temperature than the exchange force Hw lt 21 from the second magnetic layer, the laser beam incident from the substrate side passes through the second external magnet again after the recording operation. Information cannot be reproduced as it is at the output, but after the recording operation is completed, Hr becomes Hb.
By applying a magnetic field in the opposite direction, the recorded information in the second magnetic layer is transferred to the first magnetic layer, making reproduction possible.

[Embodiment] FIG. 1 shows an embodiment of the present invention, and FIG. 1(a) is a cross-sectional view of the main part, with reference numerals (1) to (4) and (7).

(8) is the same as in FIG. 3(a). The same figure (b
) is a hysteresis characteristic diagram of the first magnetic layer (3) at room temperature,
Figure (c) shows the magnetic field generated by the external magnet. Second magnetic layer (
4) Exchange force Hw1. ! The coercive force is smaller at room temperature, and the first magnetic layer (3) is aligned in the magnetization direction of the second magnetic layer (4) due to exchange force when no external magnetic field is applied at room temperature. Furthermore, at room temperature, in a magnetic film in which the rare earth metal magnetic moment is dominant, the direction of the external magnetic field applied during recording and initialization is the same. Second magnetic layer (4)
The single external magnet (8) is responsible for recording and retaining information, with its magnetization direction not being affected except when exposed to high laser power during recording.

The initialization operation is performed when the recording medium (1) moves and the second magnetic layer (4) generates a magnetic field Hini larger than the reversal magnetic field H1' in FIG. 1(b) of the single external magnet (8). Ha-
(transition metal magnetic moment is directed downward). At this time, even if the part that generates a magnetic field larger than the reversal magnetic field H1° is far away, the part that is irradiated with the laser beam (7) will have a magnetic field larger than the reversal magnetic field H1-. Magnetic field (Hb~Mi
ni), the first magnetic layer (3) is uniformly magnetized upward when directly above the single external magnet (8).

The output of the laser beam (7) is increased to form the second magnetic layer (4).
is aligned with the magnetization direction of the first magnetic layer (3) due to the exchange force, and the first
When the magnetization reversal temperature of the magnetic layer (3) is not reached, the magnetization direction of the first magnetic layer (3) is transferred to the second magnetic layer (4). At this time, the first magnetic layer (3) is initialized to face upward (transition metal magnetic moment is downward) at room temperature, so the magnetization direction of the second magnetic layer (4) is downward (transition metal magnetic moment is downward). become.

When the magnetization reversal temperature of the first magnetic layer (3) is exceeded, Hb
As a result, the magnetization direction of the first magnetic layer (3) is directed upward (the transition metal magnetic moment is directed upward), and the first magnetic layer (
The magnetization direction of 3) is transferred to the second magnetic layer (4), and the magnetization direction of the second magnetic layer (4) becomes upward (the transition metal magnetic moment is upward). The magnetization direction is determined by the temperature drop of the recording medium (1).
single external magnet (8) to occur quickly compared to the movement of
This occurs when a magnetic field is applied. When the recording medium (1) leaves the magnetic field of the single external magnet (8), the first
The magnetization direction of the magnetic layer (3) changes with respect to the second magnetic layer (4) so that the domain wall between the magnetic layers disappears.

By performing such an operation and simply changing the output of the laser beam (7), the magnetization state of the first magnetic layer (3) can be changed and direct overriding becomes possible.

To give a more specific example, Tb and C on Fe.

A light-transmitting glass substrate (2) on which groups with a pitch of 1.6 μm were previously provided was placed in a sputtering apparatus equipped with a first target source having chips arranged thereon and a second target having Tb chips arranged on Fe. The sputtering speed was 100 as the first magnetic layer (3) in an argon atmosphere.
A film thickness of 700 layers was laminated from the first target source at a thickness of 700 layers per sin. After leaving this state for half a day, a second magnetic layer (4) was deposited to a thickness of 600 layers using a second target source. At this time, the Curie temperatures of the first magnetic layer (3) and the second magnetic layer (4) are each 220°C.

The temperature is 170℃, and the coercive force at room temperature is 3kise, respectively.
>15 and 6e. Also, the exchange force at room temperature [=(domain wall energy)/2/(saturation magnetization)/(film thickness)] is 3.
2k6e, <5k6e. This medium disk is rotated at a linear speed of 6 m 1 sec, Hini=Fk
iie.

Continuously changing single magnet of Hb・400oe (8)
By using 9mW peak power, 4.5mW
Under conditions of a bottom power of 1 mW and a read power of 1 mW, perfect override characteristics were obtained for two different recording frequencies, for example, 2 MHz & 5 MHz. 1st
A reproduction output that was approximately 10% higher was obtained compared to a recording medium having the same structure as the conventional example in which the magnetic layer (3) and the second magnetic layer (4) were stacked in reverse.

FIG. 2 shows another embodiment, and FIG. 2(a) is a cross-sectional view of the main part of a magneto-optical recording medium, in which a first external magnet (5) and a second external magnet are used instead of a single magnet (8). A magnet (6) is provided. The second external magnet (6) is a permanent magnet that generates a Mini magnetic field, and the first external magnet (5) is a Hb magnetic field during recording.
, is an electromagnet that generates a magnetic field Hr in the opposite direction to Hb at the end of recording. Figure (b) shows the first magnetic layer (3) at room temperature.
), and (c) is a hysteresis characteristic diagram of the exchange force HW from the second magnetic layer (4), which shows the magnetic field generated by the external magnet.
+ + 2. The second magnetic layer (4), which has a higher coercive force at room temperature, has a magnetization direction that is not affected by the first external magnet (5) except when exposed to high laser power during recording, so that it can retain information. It is the responsibility of

The override operation is the same as in the previous embodiment, but since the coercive force is larger at room temperature than the exchange force HW++z+ from the second magnetic layer (4), after the recording operation, the second external magnet (
After passing through 6), the laser beam (7) that enters from the substrate (2) side cannot reproduce information as it is, but
After the recording operation is completed, by applying a magnetic field Hr in the opposite direction to Hb, the recorded information in the second magnetic layer (4) is transferred to the first magnetic layer (3).
) and can be reproduced. Although reversal of the magnetic field generated by the first external magnet (5) is required here, it is only associated with switching between recording and reproducing operations, so it does not seriously impede the transfer speed characteristics of the recording device.

Specifically, a group of 1.6 μ plow pitches was prepared in advance in a sputtering apparatus equipped with a first target source having Tb and Co chips on Fe and a second target having Tb chips on Fe. The light-transmitting glass substrate (2) provided is arranged, and the first magnetic layer (3) is placed in an argon atmosphere.
), a film thickness of 1000 layers was deposited from the first target source at a sputtering rate of 100 layers/win. After leaving this state for half a day, a second magnetic layer (4) was deposited to a thickness of 600 from the second target source. At this time, the first magnetic layer (3
) and the second magnetic layer (4) have a Curie temperature of 220°C, 17
0℃, and the coercive force at room temperature is 3 k5e, respectively.
>15 and 6e. Also, the exchange force [=(domain wall energy)/2/(saturation magnetization)/(film thickness)] at room temperature is 2.5
It was 6e in <5, and 6e in <5. This disk has a linear speed of 6
Rotate at m/sec, old 1i = 71 (oe ] b = 2
10-H peak power at 506e magnetic field, 5mW
Under the condition of read power of 1 mW, perfect override characteristics are obtained for two different recording frequencies, for example 2 MHzk5N13, and Hr
Reproduction was possible with a magnetic field of =-7006e.

Further, in each example, two magnetic layers were provided on the glass substrate, but a plastic substrate such as polycarbonate or boreolifin may be used as the substrate, or DyF as the magnetic layer.
eCo, GdTbFe, DyCdFeCo,
(, dFe, TbNdFeco, DyCo, etc. may be used, and a dielectric layer, a nonmagnetic layer, and a magnetic layer may also be provided.
Further, these disks may be bonded together using epoxy resin, thermoplastic resin, or the like.

[Effects of the Invention] As described above, according to the magneto-optical recording medium of the present invention, the first magnetic layer made of a rare earth-transition metal amorphous alloy having perpendicular magnetic anisotropy provided on the substrate; A second magnetic layer made of a rare earth-transition metal amorphous alloy is provided in one magnetic layer and bonded to the first magnetic layer by exchange force, and direct override is possible by using the second magnetic layer as a recording layer. , and the playback output also increases.

Further, according to the magneto-optical recording method of the present invention, even when the coercive force is greater than the exchange force from the second magnetic layer, override is possible by applying a magnetic field in the opposite direction to the recording magnetic field.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are (a) of an embodiment of the present invention, respectively.
3 is a similar diagram of a conventional magneto-optical recording medium; (b) magnetization hysteresis characteristic diagram of the second magnetic layer; (e) magnetic field characteristic diagram generated by an external magnet; be. (1)...Recording medium, (2)...Substrate, (3)...First
Magnetic layer, (4)...Second magnetic layer, (5)...First external magnet, (6)...Second external magnet, (7)...Laser beam, (8)...Single external magnet . In each figure, the same reference numerals indicate the same or corresponding parts. Broom 1 diagram

Claims (2)

[Claims] (1) A substrate, a first magnetic layer made of a rare earth-transition metal amorphous alloy having perpendicular magnetic anisotropy provided on this substrate, and a first magnetic layer provided on this first magnetic layer to replace the first magnetic layer. A second layer consisting of a force-bonded rare earth-transition metal amorphous alloy
and a magnetic layer, Tc_1>Tc_2, where Tc_1: Curie temperature Tc_2 of the first magnetic layer.
: Satisfies the Curie temperature of the second magnetic layer and at room temperature Hc_2-Hw_2_(_1_)>|Hini|>Hc
_1+Hw_1_(_2_)＞｜Hb｜Hc_1−Hw
_1_(_2_)>0 However, Hc_1: Coercive force of the first magnetic layer Hc_2: Coercive force of the second magnetic layer Hw_1_(_2_): Exchange force that the first magnetic layer receives from the second magnetic layer Hw_2_(_1_): Exchange force Hini that the two magnetic layers receive from the first magnetic layer: Initial auxiliary magnetic field Hb: Magneto-optical recording medium that satisfies the recording magnetic field. (2) (a) using the magneto-optical recording medium according to claim (1); (b) moving the magneto-optical recording medium in a certain direction; and (c) adjusting the intensity of the laser beam to perform erasing, recording, and reproduction. (d) The applied magnetic field is in a constant direction and the magnetic field strength is different between the area immediately before the laser beam is irradiated and the area where the laser beam is irradiated, and (e) From after the recording operation. Before playback operation |Hr|>Hc_1-Hw_1_(_2_)Hb・Hr
A magneto-optical recording method in which a reproduction auxiliary magnetic field Hr satisfying <0 is applied to the medium.