JPH0386954A - Magneto-optical recorder - Google Patents

Abstract

PURPOSE:To keep recording stable and to obtain high reliability by providing a first magnetic field generation means which generates a magnetic field changing the magnetization direction of a magnetic layer, a second magnetic field generation means which generates a magnetic field magnetizing a reference layer and a third magnetic field generation means which makes a magnetic wall occurring between a recording layer an the reference layer disappear. CONSTITUTION:The first outside magnet 5 which generates the magnetic field changing the magnetization direction of the magnetic layer, the second outside magnet 6 which generates the magnetic field magnetizing the reference layer 4 and the third outside magnet 8 which generates the magnetic field having an opposite direction to the second outside magnet 6 and which makes the magnetic wall A occurring between the recording layer 3 and the reference layer 4 disappear after the recording/erasing of information are provided. In such the case, since the reference layer 4 is inverted in the magnetization direction of the recording layer 3 by the third outside magnet 8 even when the magnetic wall is left between the magnetic layers after the recording/ erasing of information, the magnetic wall is not left between the magnetic layers after a recording medium 1 is passed through the third outside magnet 8. Thus, even when the recording medium 1 is exposed under a high temperature state, the recording is stable and the reliability as the recording medium 1 is improved.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention enables recording and recording of information on a recording layer by locally irradiating light onto a multilayer magnetic layer including a recording layer and a reference layer. The present invention relates to a magneto-optical recording device that performs erasing, and more particularly to a magneto-optical recording device that has been improved to provide a highly reliable magneto-optical recording medium that stably retains records.

[Prior Art] When a magnetic recording medium is locally irradiated with light and its thermal energy is used to heat the medium to near the magnetization reversal temperature, the coercive force decreases. A recording method that applies a weak external magnetic field in this state to produce residual magnetization only in the light irradiated area is called magneto-optical recording. Since a laser beam is used as a light source, high-density recording is possible.

FIG. 7 shows, for example, a publication (International
Symposium on 0ptical
Memory '87 TECHNICAL
A schematic configuration diagram of a conventional magneto-optical recording device shown in ``DIGEST'' is shown, and FIG. 8 shows a cross-sectional view of the main part thereof.

Referring to these figures, the magneto-optical recording device records information on a recording medium 1 including a recording layer 3 and a reference layer 4, and reproduces information from the recording medium 1, and basically records information. It consists of a system and a regeneration system.

The recording system includes a laser light source 13, a polarizer 11, a polarizing beam splitter 10a, a condenser lens 9, and a first external magnet that generates a magnetic field that changes the magnetization direction of the magnetic layer only with the laser beam intensity during recording erasure. 5, so that the magnetization direction of the reference layer 4 is uniform regardless of the magnetization direction of the recording layer 3.
and a second external magnet 6 that generates a magnetic field that magnetizes the reference layer 4. On the other hand, the reproduction system includes a pair of photodetectors 14 and a
It consists of a pair of analyzers 12 and a polarizing beam splitter 10b.

The laser light source 13 is configured so that the output of the recording/erasing/reading laser beam 7 can be controlled in three stages. In the figure, 15
indicates bits written on recording medium 1.

Referring to FIG. 8, the recording medium 1 includes a transparent substrate 2,
It is composed of a recording layer 3 and a reference layer 4.

The recording layer 3 and the reference layer 4 are formed of a rare earth-transition metal alloy, and the rare earth metal and the transition metal each form a sublattice. Sublattice magnetization is given as the sum of the magnetic moments responsible for the magnetism of each sublattice, and magnetization is given as the sum of the sublattice magnetizations. In addition, in the case of ferrimagnetic materials, the directions of rare earth metal sublattice magnetization and transition metal sublattice magnetization are opposite, and the relationship between the magnetization direction and the direction of transition metal sublattice magnetization, for example, depends on the composition of the magnetic layer and the temperature. Although it varies depending on
Between each magnetic layer, an exchange coupling force acts to align the sublattice magnetizations of transition metals, for example, between the magnetic layers. In this conventional example, a magnetic material is used in which the transition metal sublattice magnetization is more dominant than the rare earth metal sublattice magnetization at room temperature, and the direction of the magnetization and, for example, the transition metal sublattice magnetization coincide with each other above room temperature.

The recording layer 3 is a layer for holding information, and the reference layer 4 is an auxiliary layer that does not have the role of a record carrier to enable direct override. The first external magnet 5 generates a magnetic field that changes the magnetization direction of the magnetic layer only with the laser beam intensity during recording and erasing.

The second external magnet 6 generates a magnetic field that uniformly magnetizes the reference layer 4 in the magnetization direction regardless of the magnetization direction (sublattice magnetization direction) of the recording layer 3 . At this time, the magnetization direction (sublattice magnetization direction) of the recording layer 3 is not affected by the exchange force acting from the external magnet and the reference layer 4, and maintains the same direction.

Next, the operation will be explained.

By increasing the output of the laser beam 7, each sublattice magnetization direction of the recording layer 3 is aligned with the sublattice magnetization direction of the reference layer 4 due to the exchange force, and the sublattice magnetization of the reference layer 4 is not reversed by the first external magnet 5. At this time, the sublattice magnetization direction of the reference layer 4 is transferred to the recording layer 3, and the sublattice magnetization direction of the recording layer 3 becomes upward. When the magnetization of the reference layer 4 reaches a temperature at which magnetization reversal occurs due to the magnetic field from the first external magnet 5 (magnetization reversal temperature), the first
The magnetization direction of the reference layer 4 is directed downward by the external magnet 5,
Further, the magnetization direction of the reference layer 4 is transferred to the recording layer 3, and the magnetization direction of the recording layer 3 becomes downward (the sublattice magnetization also becomes downward). In this way, by simply changing the output of the laser beam 7, the magnetization direction (sublattice magnetization direction) of the recording layer 3 can be changed, making direct override possible. However, referring to FIG. 9, after erasure, the reference layer 4 is magnetized upward by the second external magnet 6, so the output of the laser beam 7 exceeds the magnetization reversal temperature of the reference layer 4. In the portion where recording was performed, a domain wall A is generated between the magnetic layers.

[Problems to be Solved by the Invention] Since the conventional magneto-optical recording device is configured as described above, referring to FIG. However, when exposed to high temperatures, the magnetization direction of the recording layer 3 of the record carrier is influenced by the reference layer 4, causing problems such as deterioration and disappearance of recording, and a lack of reliability as a recording medium.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a magneto-optical recording device that stably retains recording and provides a highly reliable magneto-optical recording medium.

[Means for Solving the Problems] The present invention provides a method of recording and erasing information on the recording layer by locally irradiating light onto a multilayer magnetic layer including a recording layer and a reference layer. This relates to a magnetic recording device. The magneto-optical recording device includes a first magnetic field generating means that generates a magnetic field that changes the magnetization direction of the magnetic layer only at the light intensity during information recording/erasing, and a first magnetic field generating means that generates a magnetic field that changes the magnetization direction of the above-mentioned magnetic layer regardless of the magnetization direction of the above-mentioned recording layer. a second magnetic field generating means for generating a magnetic field that magnetizes the reference layer so that the magnetization direction of the layer is uniform;
It is equipped with Furthermore, in order to solve the above problem, the magneto-optical recording device generates a magnetic field in the opposite direction to the second magnetic field generating means, and after recording/erasing information, the magnetic field is generated between the recording layer and the reference layer. The magnetic field generating means is provided with a third magnetic field generating means for eliminating the domain wall generated in the magnetic field.

[Function] The magneto-optical recording device according to the present invention includes a third layer that eliminates the domain wall generated between the recording layer and the reference layer after recording and erasing information.
Since the magnetic field generating means is provided, it is possible to eliminate domain walls remaining between the magnetic layers of the magneto-optical recording medium.

Embodiment FIG. 1 shows a schematic diagram of a magneto-optical recording apparatus according to an embodiment of the present invention, and FIG. 2 is a sectional view of the main parts thereof. FIG. 3 shows the completion of recording of the above-mentioned magneto-optical recording device (■, 1?). FIG. 4 is a sectional view of the main parts thereof.

The embodiment shown in FIGS. 1 to 4 is similar to the conventional example shown in FIGS. 7 and 8 except for the following points, and corresponding parts are given the same reference numerals. The explanation will be omitted.

The embodiment shown in FIGS. 1 to 4 differs from the conventional example shown in FIGS. 7 and 8 in that a magnetic field is generated in the opposite direction to that of the second external magnet 6, and after recording/erasing information, The third external magnet 8 is provided to eliminate the domain wall A generated between the recording layer 3 and the reference layer 4.

The recording layer 3 and the reference layer 4 are made of a magnetic material in which the transition metal sublattice magnetization is more dominant than the rare earth metal sublattice magnetization at room temperature, and the direction of the magnetization and, for example, the transition metal sublattice magnetization match at room temperature or higher. There is. At this time, since each magnetic layer is coupled by exchange force, the hysteresis curve of the reference layer 4 is as shown in FIG. 5(a) when the magnetization of the recording layer is upward (transition metal sublattice magnetization is upward). When the magnetization of the recording layer 3 is downward (transition metal sublattice magnetization is downward), the magnetic field is shifted upward in the direction of the magnetic field as shown in Figure 5(b). Become.

In this asymmetric hysteresis curve, a switching magnetic field with a large absolute value is defined as H2+, and a switching magnetic field with a small absolute value is defined as H2-.

The third external magnet 8 has a reversal magnetic field H2- of the reference layer 4 at room temperature.
It generates a magnetic field in the opposite direction to the second external magnet 6, with a magnitude intermediate between ``2+'', and is separated from the recording medium 1 during normal recording operation, as shown in FIGS. 1 and 2. When taking out the recording medium 1 from the recording apparatus, as shown in FIGS. 3 and 4, after the external magnet 6 is separated from the recording medium 1, the rotation time is longer than the time for the recording medium 1 to rotate once. , the third external magnet 8 moves toward the recording medium 1 such that a magnetic field is applied to the recording medium 1 .

Next, the operation will be explained.

When the third external magnet 8 acts on the recording medium 1 when the recording medium 1 is taken out from the recording device, the area where domain walls remain between the magnetic layers after recording and erasing, as shown in part A in FIG. ,
By applying a magnetic field in the opposite direction to the second external magnet 6 between the reversal magnetic fields H2- and H2+, the recording layer 3 remains unchanged;
``The magnetization of the reference layer 4 is reversed, and the domain wall between the magnetic layers disappears (see section C in FIG. 4). In a region where no domain wall remains, such as part B, the magnetization direction of the magnetic layer does not change due to the third external magnet 8.

With this configuration, even if a domain wall remains between the magnetic layers after recording and erasing, the third external magnet 8 can move the reference layer 4
is reversed in the magnetization direction of the recording layer 3, so that no domain wall remains between the magnetic layers after passing through the third external magnet 8. As a result, when the recording medium is stored, there are no domain walls between the magnetic layers and the recording medium is in a magnetically stable state, so even if exposed to high temperatures, recording is stable and reliability as a recording medium is improved.

FIG. 6 shows the error rate when a recording medium on which information has been previously recorded is exposed to high temperature in a magnetic field. A recording medium recorded with a conventional magneto-optical recording device has a magnetic field of 6006e and a temperature of 60°C.
Alternatively, recording deterioration occurred at zero magnetic field and temperature of 80°C, but in the recording medium recorded by the magneto-optical recording device of this example,
Even at a magnetic field of 600″C3e and a temperature of 100°C, no change appeared in the recorded signal.

In the above embodiment, the first external magnet 5 and the third external magnet 8 are configured as separate magnets. However, by using an electromagnet as the first external magnet 5, this electromagnet applies a magnetic field to the recording medium 1 with a magnitude intermediate between the reversal magnetic field H2-1H2+ of the reference layer 4 at room temperature and in the opposite direction to the second external magnet 6. When taking out the recording medium from the recording apparatus, that is, after the second external magnet 6 is separated from the recording medium 1, the recording medium may be subjected to a time longer than that for the recording medium 1 to rotate once. In this case, the magneto-optical recording medium 1 is H2''#4k'c5 e, H2
#0.8 to 6e, and the above magnetic field is 1 to 2
It is necessary to apply approximately k'Cj e. The first external magnet 5 generates a magnetic field of about 200 to 6006 e during erasing and recording, and even such electromagnets currently used cannot generate a magnetic field of more than 11 c'Cj e on the recording medium 1.
It is sufficient to generate several tens of milliseconds, which is the time required for one rotation of the rotor. Even when such an apparatus is used, a highly reliable magneto-optical recording medium can be obtained without loss of recorded information even under harsh storage environments, as in the above embodiments. In this case, there is no need to separately and independently install the third external magnet 8, so there is also the effect that the device can be prevented from becoming complicated.

Further, the third external magnet 8 may also be used as the first external magnet 5 or the second external magnet 6 by mechanically changing the polarity and magnetic field strength on the medium surface, and may be provided in a device other than the recording/reproducing device. Good too. Furthermore, a thin film magnet or the like may be provided directly on the recording medium. Furthermore, the recording medium may be a double-sided medium in which TIt board disks are bonded together.

[Effect of the invention] As explained above, according to this invention, information recording and
Since the third magnetic field generating means is provided to eliminate the domain wall generated between the recording layer and the reference layer after erasing, the domain wall remaining between the magnetic layers of the magneto-optical recording medium can be eliminated. As a result, it is possible to obtain a highly reliable magneto-optical recording medium that can withstand long-term storage.

[Brief explanation of drawings]

FIG. 1 shows a schematic configuration diagram of a magneto-optical recording device according to an embodiment of the present invention during recording, and FIG. 2 is a sectional view of the main parts thereof. FIG. 3 shows a schematic configuration diagram of a magneto-optical recording device according to an embodiment of the present invention during the end of recording, and FIG. 4 is a sectional view of the main part thereof. FIG. 5 is a hysteresis characteristic diagram of the reference layer, in which (a) is a diagram when the magnetization of the recording layer is upward, and (b) is a diagram when the magnetization of the recording layer is downward. FIG. 6 is a graph showing the error rate characteristics of the recording media obtained in the conventional example and the present example with respect to input temperature and magnetic field. FIG. 7 is a block diagram of a conventional magneto-optical recording device, and FIG. 8 is a sectional view of its main parts. FIG. 9 is a cross-sectional view showing the state of a magneto-optical recording medium produced by a conventional magneto-optical recording device after recording and erasure. In the figure, 1 is a recording medium, 3 is a recording layer, 4 is a reference layer,
5 is a first external stone, 6 is a second external magnet, 7 is a laser beam, 8 is a third external magnet, and A is a domain wall. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] By locally irradiating light onto a multilayer magnetic layer including a recording layer and a reference layer, information can be recorded and recorded on the recording layer.
A magneto-optical recording device that performs erasing, comprising: a first magnetic field generating means that generates a magnetic field that changes the magnetization direction of the magnetic layer only with the light intensity when recording and erasing information; and the magnetization direction of the recording layer. Regardless, a second magnetic field generation means for generating a magnetic field that magnetizes the reference layer so that the magnetization direction of the reference layer is uniform, and a magnetic field generated in the opposite direction to the second magnetic field generation means, A magneto-optical recording device comprising: third magnetic field generating means for eliminating a domain wall generated between the recording layer and the reference layer after recording/erasing information.