JPH01227245A - Magneto-optical recording system - Google Patents

Abstract

PURPOSE:To improve the stability of recorded information by providing a recording layer and an initializing layer which are made of rare earth-iron family amorphous alloy and have composition opposite to compensatory composition and bringing interfacial magnetic wall into existence outside a recording magnetic domain after an initialization. CONSTITUTION:A recording layer 1 and an initializing layer 2 which are make of the rare earth-iron family amorphous alloy and have the composition opposite to the compensatory composition are provided on a substrate. After the initialization, laser power is modulated and recorded so that an interfacial magnetic wall 5 may exist outside a cylindrical magnetic domain 3. Here, a Bloch magnetic wall 4 and a magnetic wall 5 reduce their areas, the magnetic wall works so as to crush the recording magnetic domain 3 and the magnetic wall 5 works so as to enlarge the magnetic domain 3. Consequently, the magnetic walls 4 and 5 works in opposite directions and works so as to cancel each other. Thus, the stability of the recorded information of an overwritable magneto-optical recording medium can be improved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an overwritable magneto-optical recording medium using a Curie point recording type magneto-optical recording medium that can be read using the magnetic Kerr effect. Regarding improvement of the method.

(Prior art) Magneto-optical memory is known as an erasable optical memory.Magneto-optical memory allows for higher density recording and non-contact recording and playback compared to magnetic recording media using conventional magnetic heads. On the other hand, it had the disadvantage that the recorded area had to be erased (magnetized in one direction) before recording.In order to compensate for this disadvantage, the recording/reproducing head was Proposed methods include a method in which a recording head and an erasing head are provided separately, or a method in which recording is performed while irradiating a continuous laser beam and simultaneously modulating the applied magnetic field.

However, these methods have drawbacks such as requiring large-scale equipment and high cost, or being unable to perform high-speed modulation.

Therefore, a magneto-optical recording system has been proposed that enables overwriting similar to that of a magnetic recording medium by simply adding a magnetic field generating means of a simple structure to the conventional device configuration. (Applicant's Japanese Patent Application No. 62-20384, No. 3
Proceedings of the 4th Applied Physics Association Lectures (1987) 2
8p-ZL-3 etc.).

This method uses an exchange-coupled two-layer structure consisting of a recording layer with a low Curie temperature and high coercive force, and an initialization layer with a relatively high Curie temperature and low coercive force compared to this recording layer. A perpendicularly magnetized film is used as a recording medium.

When the recording medium is initialized by an initializing magnetic field by modulating the laser intensity to "high" and "low" in response to the recording signal "1" and "0", for example, a second The magnetization state is as shown in the figure.

(Problems to be Solved by the Invention) In FIG. 2, rare earth-iron group amorphous alloy thin films having the same composition with respect to the compensation composition are considered, for example, as the recording layer and the initialization layer. Here, 4 is a domain wall (Bloch domain wall) formed on the side surface of the cylindrical magnetic domain 3 recorded in the recording layer 1,
Reference numeral 5 denotes a domain wall (interface domain wall) formed at the boundary between the cylindrical magnetic domain and the initialization layer 2. Here, the domain wall is a transition region where the magnetic moment gradually changes its direction, and stores a certain amount of energy, and the domain wall always tries to reduce its area.

In this figure, both the Bloch domain wall and the interface domain wall try to reduce their areas (the area where the magnetization of the recording domain is stabilized tries to expand), so they both act to collapse the recording domain. Furthermore, since the initializing magnetic field 6 also acts in a direction to reduce the area of the Bloch domain wall, the recording magnetic domain becomes even more unstable.

The present invention is intended to eliminate the drawbacks of the above-mentioned conventional example, and provides a recording method that improves the stability of recorded information by making an interface domain wall exist outside the recorded cylindrical magnetic domain. With the goal.

(Means for Solving the Problems) The present invention capable of achieving the above-mentioned objects comprises a recording layer having a low Curie temperature and high coercive force, and an initial stage having a relatively high Curie temperature and low coercive force compared to the recording layer. In a magneto-optical recording method using a magneto-optical recording medium that can be overwritten by modulation of laser power and has a perpendicularly magnetized film with an exchange-coupled two-layer structure on a substrate, the method uses This is a magneto-optical recording method characterized by recording while modulating laser power so that an interfacial domain wall exists outside the cylindrical magnetic domain recorded in the recording layer.

, rare earth-iron group amorphous alloy thin films having compositions opposite to each other with respect to the compensation composition are used as the recording layer and the initialization layer, and after initialization, an interface is formed on the outside of the cylindrical magnetic domain recorded in the recording layer. A particularly preferred embodiment is to record by modulating the laser power so that the magnetization of the cylindrical magnetic domain recorded in the recording layer and the magnetization of the initialization layer are antiparallel to each other so that a domain wall exists. It is.

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows the electrification state according to the recording method of the present invention. In this method, recording is performed by modulating the laser intensity to "low" and "high", respectively, corresponding to "1" and "0" of the recording signal.

FIG. 1 shows a state where initialization was then performed using an initialization magnetic field.

In this embodiment, the interface domain wall 5 exists outside the recording magnetic domain 3. Further, it is preferable to use rare earth-iron group amorphous alloy thin films having compositions opposite to each other with respect to the compensation composition as the recording layer and the initialization layer. At this time, both are stable with their magnetizations being antiparallel.

In Figure 1, the Bloch domain wall 4 and the interface domain wall 5 try to reduce their area, but the Bloch domain wall acts to crush the recording domain (reducing the area that stabilizes the magnetization of the recording domain). On the other hand, the interfacial domain wall acts to widen the recording magnetic domain (enlarging the region where the magnetization of the recording domain is stabilized). Therefore, since the Bloch domain wall and the interface domain wall act in opposite directions, their effects cancel each other out, improving the stability of the recording magnetic domain.

In this case, if the energy densities of the Bloch domain wall and the interfacial domain wall are the same, the ratio of the effect of the Bloch domain wall to the effect of the interfacial domain wall is equal to the ratio of the diameter of the recording magnetic domain to the film thickness of the recording layer.

Since the diameter of the recording magnetic domain is generally larger than the film thickness, the effects of the two do not cancel each other out, but the effect of expanding the interfacial domain wall or the magnetic domain remains.

Even if rare earth-iron group amorphous alloy thin films with compositions on the same side of the compensation composition are used as the recording layer and initialization layer, the stability of the magnetic domain is increased by creating an interfacial domain wall outside the recording magnetic domain. However, if the initializing magnetic field can be applied in a direction that collapses the magnetic domains, the interfacial magnetic wall cancels out the effect of expanding the magnetic domains, thereby further improving recording stability.

In order to apply the initialization magnetic field in the direction of crushing the magnetic domains, the first
As shown in the figure, rare earth-iron group amorphous alloy thin films having compositions opposite to each other with respect to the compensation composition are used as the recording layer and the initialization layer, and the magnetization of the recording magnetic domain and the magnetization of the initialization layer are antiparallel to each other. It is better to make it so that

In order to completely cancel out the effects of the Bloch domain wall and the interface domain wall, it would be possible to increase the thickness of the recording layer, but this is not practical because the recording sensitivity deteriorates. Instead, it is better to lower the energy density of the interfacial domain wall. For this purpose, a perpendicularly magnetized film (Gd-Fe, Gd-Fe-G
o, Gd-Go, Gd-Tb-Fe, Gd-Tb
-Fe-fl:o, Gd-Tb-Go, etc.), or in-plane magnetized film (Fe, Go, Ni, or highly magnetized Gd-Fe, Gd-1Fe-Go, Gd-1o,
Gd-Tb-Fe, Gd-Tb-Fe-Go, Gd
-Tb-Go, etc.).

[Example 1] A polycarbonate disc-shaped substrate on which pregroup and preformat signals are engraved is placed in a sputtering apparatus equipped with a ternary target at a distance it1 between the target and the sputtering apparatus.
They were set at 15 cm intervals and rotated.

Sputtering speed 4 from the first target in argon
0 people/min, sputtering pressure 1.5 x 10-'Pa S
A protective film of i3N4 was applied to a thickness of 500 mm. Next, in argon, a sputtering speed of 1 was applied from the second target.
00 people/min, sputtering pressure 1, 5x 10-'P
A Tb-Fe alloy was sputtered with a film thickness of 500 mm and T(
Curie temperature) L = approx. 130°C, H (coercive force) = approx. 1
5, a recording layer of Oe in which Fe sublattice magnetization was dominant was formed.

Next, in argon, a third target was sputtered at a sputtering rate of 100 people/min, and a sputtering pressure of 1.5×10-'P.
Gd-Tb-Fe-Go gold alloy sputtered in a,
Film thickness: 700 mm, T = approx. 220°C, HL = approx. 4 KOe
, an initialization layer with dominant Gd-Tb sublattice magnetization was formed at a compensation temperature of about 140°C.

Next, the first evening in argon! sputtering speed 4 than get
0 people/min, sputtering pressure 1.5X10-'Pa,
A protective layer of Si3N4 was applied to a thickness of 700 nm.

Next, the substrate on which the film had been formed was bonded to a polycarbonate bonding substrate using hot melt and adhesive to produce a magneto-optical disk. This magneto-optical disk was set in a recording/reproducing device, and while applying a bias magnetic field of 2000e and an initialization magnetic field of 2 Oe,
mm/sec, focused at approximately 1.5-8 30
nm wavelength laser beam with a duty of 50%.
3.8 mW and 6.4 m while modulating at 2 MHz.
Recording was performed using a binary W laser power. After that, 1
When regeneration was performed by irradiating a mW laser beam, a binary signal could be regenerated.

Next, after performing the above experiment, 3
Recordings were made at MHz and at the same power. As a result, it was confirmed that previously recorded signal components were not detected and overriding was possible.

Recording according to the present invention (recording corresponding to claim 2) is performed on this disc by modulating the laser intensity to "low" and "high", respectively, corresponding to "1" and "0" of the recording signal. After that, the temperature was 70℃ and the initialization magnetic field was 2 KOe.
Although the time was saved, there was no change in the recorded information.

[Comparative Example 1] Instead of recording according to the present invention, recording was performed on the disc of Example 1 by modulating the laser intensity to "high" and "low" in response to recording signals "1" and "0", respectively. After doing this, the temperature is 7.
When stored for 100 hours in an environment of 0° C. and an initialization magnetic field of 2 KOe, the recorded information was found to have changed.

[Example 2] As the initialization layer, a sputtering rate of 1 was applied from the third target.
Gd-Tb-Fe-Go gold alloy was sputtered at a sputtering pressure of 1.5 x 10-'Pa at a sputtering rate of 00 people/min, with a film thickness of 700 people, T=approximately 220°C, H=approximately 5 KOe of F.
Except for forming an initialization layer with dominant e-Go sublattice magnetization,
A magneto-optical disk similar to that in the example was prepared and a similar experiment was conducted.

As a result, it was confirmed that override is possible.

Recording according to the present invention (recording included in claim 1) is performed on this disk by modulating the laser intensity to "low" and "high", respectively, corresponding to "1" and "0" of the recording signal. After that, the temperature was 50°C and the initialization magnetic field was 2 KOe.
Although the time was saved, there was no change in the recorded information.

[Comparative Example 2] Instead of recording according to the present invention, recording was performed on the disk of Example 2 by modulating the laser intensity to "high" and "low" in response to recording signals "1" and "0", respectively. After performing
When stored for 100 hours in an environment of 0° C. and initialization magnetic field 2 and Oe, the recorded information was found to have changed.

The states of magnetization after recording in Example 1.2 and Comparative Example 1.2 are shown in FIGS. 3 to 6 in order.

〔Effect of the invention〕

As explained in detail above, an exchange-coupled double layer consisting of a recording layer having a low Curie temperature and high coercive force, and an initialization layer having a relatively high Curie temperature and low coercive force compared to the recording layer. Using a magneto-optical recording medium having a layered perpendicularly magnetized film on a substrate, after initialization, the laser power is modulated so that an interfacial domain wall exists outside the cylindrical magnetic domain recorded in the recording layer. At the same time, the stability of the recorded magnetic domain was improved in the overwritable recording method.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a recording state according to the recording method of the present invention, FIG. 2 is a diagram showing a recording state according to a conventional overwritable recording method, and FIGS. FIG. 2 is a diagram showing the state of magnetization after recording in Comparative Example 3.4. 1: Recording layer, 2: Initialization layer, 3: Cylindrical magnetic domain, 4: Bloch domain wall, 5: Interface domain wall,
6: Initialization magnetic field.

Claims (1)

[Claims] 1) a recording layer having a low Curie temperature and a high coercive force;
Overwriting by laser power modulation, which has a perpendicularly magnetized film with an exchange-coupled two-layer structure on a substrate, which is composed of an initialization layer having a relatively high Curie temperature and low coercive force compared to the recording layer. In the magneto-optical recording method using a possible magneto-optical recording medium, after initialization, the laser power is modulated so that an interfacial domain wall exists outside the cylindrical magnetic domain recorded in the recording layer.
A magneto-optical recording method characterized by recording. 2) As the recording layer and the initialization layer, rare earth-iron group amorphous alloy thin films having compositions opposite to each other with respect to the compensation composition are used, and after initialization, the magnetization of the cylindrical magnetic domain recorded in the recording layer and 2. The magneto-optical recording method according to claim 1, wherein recording is performed so that the magnetizations of the initialization layers are antiparallel to each other.