JP2604702B2 - Magneto-optical recording / reproduction / erasing method and apparatus - Google Patents

Description

The present invention relates to a magneto-optical recording / reproducing / erasing method and apparatus for recording / reproducing / erasing information by switching between a laser beam and an applied magnetic field.

(Prior art and its problems) The optical recording method, especially the optical disk memory method,
In recent years, it has attracted attention as one of large-capacity file memories because it can perform large-capacity recording and can also perform non-contact and high-speed access. Among them, MnB as a recording medium
crystalline magnetic thin films such as i, MnCuBi, MnTiBi, MnAlGe or
Magneto-optical disk memory using an amorphous magnetic thin film made by combining rare earth metals such as Tb, Gd, Dy, Ho and transition metals such as Fe, Co, Ni, etc. Due to its advantages, it is being actively studied in various places.

Conventionally, in a known magneto-optical recording / reproducing / erasing method, the following operations are performed for recording / reproducing / erasing information.

For recording, heat generated by a laser beam is used. The laser light beam is narrowed down to a minute spot of 1 to 2 μmφ and irradiated on the recording medium to raise the medium temperature. When performing Curie temperature recording, the recording medium is raised to a Curie temperature or higher, and a reversal magnetic domain is formed by an externally applied magnetic field or a demagnetizing field of the recording medium. When performing compensation temperature recording, set the compensation temperature of the recording medium to around room temperature, raise the temperature to a certain temperature by irradiating a laser light beam, and form a reversal magnetic domain by an externally applied magnetic field using the decrease in the coercive force of the medium. . By the means described above, the recording binary signals "1" and "0" can be recorded in a form corresponding to the presence or absence of the reversal magnetic domain of the recording medium.

Reproduction is performed using a magneto-optical effect (Kerr effect or Faraday effect). That is, information is read from the recording medium by utilizing the fact that the polarization plane of reflected light or transmitted light from the medium is rotated according to the presence or absence of the reversal magnetic domain of the recording medium. The recording medium is irradiated with a laser beam having a lower power level than during recording, and a signal is reproduced from the reflected light or transmitted light.

When erasing recorded information, an external magnetic field is applied with a polarity opposite to that during recording, and the recording medium is uniformly irradiated with a laser beam at the same intensity as during recording. By applying an external magnetic field, the magnetization state of the recording medium returns to the initial state before recording.

Here, the known external magnetic field applying means is, for example, a method using an air core coil, a method using an electromagnet, or a method using a permanent magnet.

In the conventional magneto-optical recording / reproducing erasing method and apparatus, rewriting of recorded information is performed in two steps of first erasing recorded information according to the erasing operation, and then recording new recorded information according to the recording operation. Perform the operation of. At this time, the direction of the external magnetic field applied to the recording medium is opposite between the time of erasing and the time of recording. Therefore, the direction of the externally applied magnetic field must be switched between the time of erasing and the time of recording. For example, when an external magnetic field is applied by an air-core coil or an electromagnet, as shown in FIG. 4, during recording and erasing, a method and apparatus for switching the direction of a current flowing through a coil in synchronization with a recording operation and an erasing operation of a laser beam. It has been known. Here, a magneto-optical disk, 22 is a magnetic field generating means, 23 is a current source, and S is an optical head. In the conventional method, it is necessary to vary the externally applied magnetic field of 300 Oe or more during recording and erasing. Therefore, there is a disadvantage that the air-core coil or the electromagnet is enlarged.

When an external magnetic field is applied using a permanent magnet as the magnetic field generating means 24, a magnet driving mechanism is used as shown in FIG. 5, but there is a disadvantage that the device configuration becomes complicated.

(Object of the Invention) An object of the present invention is to solve the drawbacks of the conventional magneto-optical recording / reproducing / erasing method and apparatus, and to provide a novel magneto-optical recording / reproducing / erasing method capable of recording / reproducing / erasing information with a simple apparatus configuration. It is to provide a device.

(Constitution of the Invention) According to the present invention, in a magneto-optical recording / reproducing / erasing method in which a magnetic thin film having perpendicular magnetic anisotropy is used as a recording medium and information is recorded / reproduced / erased by applying a laser beam and a magnetic field, The demagnetization state as an initial state, irradiating a laser beam of a constant intensity, a high-speed switching of an applied magnetic field according to recording information to form a magnetic domain in the recording medium, and a recording direction of the magnetic domain of the recording medium. Magneto-optical recording, comprising: a reproducing step of reproducing information from a corresponding rotation of the plane of polarization of reflected laser light; and an erasing step of returning the magnetization state of the recording thin film to a demagnetized state by applying a magnetic field and irradiating a laser beam. A magneto-optical recording / reproducing / erasing apparatus using the magneto-optical recording / reproducing / erasing method, wherein the recording medium has a demagnetized state of a magnetic thin film as an initial state, An optical head for irradiating a medium with laser light of a constant intensity, a magnetic field generating means for applying a magnetic field relative to recording, and a magnetic field intensity generated by the magnetic field generating means during recording can be changed according to recording information; A magneto-optical recording / reproducing and erasing apparatus characterized by comprising a magnetic field modulating means for returning the magnetization state of the magnetic thin film to a demagnetized state while keeping the intensity of the magnetic field generated by the magnetic field generating means constant.

(Detailed Description of Configuration) The present invention has solved the problems of the prior art by adopting the above configuration. Hereinafter, details of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of a magneto-optical recording / reproducing / erasing apparatus to which the present invention is applied. In FIG. 1, a magneto-optical disk 1 has a magnetic thin film 3 having an axis of easy magnetization in a direction perpendicular to the substrate surface formed on one or both surfaces of a disk 2 made of an organic resin substrate, a glass substrate, or a metal substrate.

The magnetic thin film 3 is a crystalline or amorphous magnetic thin film. And an amorphous magnetic thin film formed by a combination with a transition metal such as Ni. The magneto-optical disk 1 is rotated at a predetermined speed by a disk drive motor 4. The optical head 5 has an optical system for magneto-optical recording / reproduction and erasing, and a light detecting mechanism. The optical head 5 itself is movable at a predetermined speed in the radial direction of the magneto-optical disk 1 as indicated by an arrow in the figure. In the optical head 5, reference numeral 6 denotes a linearly polarized laser light source, for example, a semiconductor laser. 7, 8, and 9 are beam splitters. The laser light beam focusing lens 10 is supported by an actuator 11. The magnetic field generating means 12 is provided on the opposite side or the same side as the optical head 5 via the magneto-optical disk 1, and is preferably an air-core coil.

The focus error signal and the tracking error signal are detected by the focus error detecting light receiving element 13 and the tracking error detecting light receiving element 14, respectively, input to the servo control circuits 15 and 16, become servo signals, and are fed back to the actuator 11. After passing through the polarization filter 17, the reproduction signal is detected by the reproduction signal detection light-receiving element 18 and amplified by the reproduction signal amplifier circuit 19.
As the polarization filter 17, for example, a Glan-Thompson prism is used. As the reproduction signal detecting light receiving element 18, for example, a PIN photodiode or an avalanche photodiode is used.

The current source 20 can be used to modulate the magnetic field generating means 12 according to the recording information, and the current supplied to the air-core coil during recording is varied according to the recording information. On the other hand, at the time of erasing, a current is supplied to the magnetic field generating means 12 so that a magnetic field necessary for erasing is obtained.

A current source 21 for supplying a current to the laser light source 6 is adjusted so that a constant output laser power can be applied to the magneto-optical disk 1 during recording, reproduction, and erasing.

Next, the operation method of the magneto-optical recording / reproducing / erasing apparatus having the above-described configuration, particularly a recording method and an erasing method different from the conventional method will be described with reference to FIG. The magnetization state of the track of the magneto-optical disk 1 has already been demagnetized as shown in FIG. 2 (a).

When recording information shown in FIG. 2 (b) is recorded on the magneto-optical disk 1, a disk track to be recorded is shown in FIG. 2 (c).
When irradiating the laser power (Pw) of a constant level shown in modulated with recorded information as shown in FIG. 2 (d) at the same time magnetic field (amplitude ± Hw, bias H _B) subjecting the. This is the current source
Adjustable at 20. At this time, magnetic domains are formed in the disk track according to the recording information having a Kerr rotation angle of ± θ _k as shown in FIG. 2 (e). Subsequently, when erasing is performed, a predetermined level of laser power (P _E ) is applied to the already-recorded tracks of the disk, and a certain level of magnetic field (H _E ) is supplied. At this time, the disc track is
The state returns to the magnetized state shown in FIG.

(Example) According to the magneto-optical recording / reproducing / erasing apparatus shown in FIG. 1 and the operation method shown in FIG. 2, information was recorded, reproduced and erased on the magneto-optical disk. 12 as a magneto-optical disk
A disk was used in which a TbFe film was formed to a thickness of 800 mm on a 0 mmφ resin substrate by a sputtering method. 0.8 width on board in advance
A pre-groove substrate in which a groove having a pitch of 2.5 μm and a depth of 700 ° was formed was used. As a protective film on TbFe film
SiO ₂ is formed at 1200 °.

An air-core coil (outer diameter 6.0 mmφ, inner diameter 2.0 mmφ, coil length 0.5 mm, number of turns 100) using a coated copper wire with a diameter of 0.1 mmφ as a magnetic field generating means 12 in FIG.
Turn), and a wire diameter of 0.1 mm for generating the modulated magnetic field
An air-core coil using a coated copper wire of φ (outer diameter 2.6mmφ, inner diameter
1.0mmφ, coil length 0.7mm, number of turns 56).

First, after the whole disk was perpendicularly magnetized in one direction in a magnetic field of 10 KOe, the disk was rotated at a linear velocity of 9 m / sec, and a laser beam of 4 mW was irradiated over one track and a magnetic field of 140 Oe was applied in the same direction as the magnetization. . This operation confirmed that the track was in a demagnetized state by observation with a polarizing microscope.

Next, P _W = 4 mW and H _B = 140 for the track in the demagnetized state.
Recording was performed with the _HW changed at a frequency of 1 MHz under the condition of 0e.

Figure 3 shows the relationship between the reproduction C / N and H _W. H _W playback C / N is saturated with more than 100 Oe, good recording is achieved.

The recording track was erased by irradiating a laser beam of 4 mW and applying a magnetic field of 140 Oe (in the same direction as the magnetization). There was no erasure over one track, and the track was completely erased.

(Effects of the Invention) As described above, according to the present invention, the following effects are obtained as compared with the conventional example.

The variable range of the applied magnetic field is as small as about ± 100 Oe, so that the magnetic field generating means can be reduced in size and simplified.

Since recording is performed by a magnetic field change according to the recording information, there is no need to modulate the laser light source as in the related art.

During recording, the magnetic field applied during erasing _{(H W, H B, H} E) so can be varied independently, the present invention can be applied to the magneto-optical disk using a variety of magnetic thin film.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a magneto-optical recording / reproducing and erasing apparatus to which the present invention is applied, and FIG. 2 is a schematic diagram showing an operation mode and a recording state of each unit at the time of recording. FIG. 3 is a view showing a measurement result of one embodiment of the present invention. FIGS. 4 and 5 are block diagrams of a conventional magneto-optical recording / reproducing / erasing apparatus. In the figure, 1 is a magneto-optical disk, 2 is a disk, 3 is a magnetic thin film, 4 is a disk drive motor, 5 is an optical head, 6 is a laser light source, 7, 8, and 9 are beam splitters, and 10 is a laser light beam collector. Optical lens, 11 is an actuator, 12, 22, 24 are magnetic field generating means, 13 is a light receiving element for focus error detection, 14
Is a tracking error detecting light receiving element, 15 and 16 are servo control circuits, 17 is a polarization filter, 18 is a reproducing signal detecting light receiving element, 19 is a reproducing signal amplifying circuit, 20 and 23 are current sources for magnetic field generating means, 21 is This is a laser current source.

Claims (2)

(57) [Claims] 1. A magneto-optical recording / reproducing and erasing method for recording / reproducing / erasing information by applying a laser beam and a magnetic field to a magnetic thin film having perpendicular magnetic anisotropy as a recording medium. And irradiating a laser beam of a constant intensity, a recording process of forming a magnetic domain in the recording medium by rapidly switching an applied magnetic field according to recording information, and a laser reflected light corresponding to a magnetization direction of the magnetic domain of the recording medium. A magneto-optical recording / reproducing / erasing method comprising: a reproducing step of reproducing information from a polarization plane rotation; and an erasing step of returning a magnetization state of the recording thin film to a demagnetized state by applying a magnetic field and irradiating a laser beam. 2. A recording medium for initializing a demagnetized state of a magnetic thin film, an optical head for irradiating the recording medium with a laser beam having a constant intensity, a magnetic field generating means for applying a magnetic field to the recording medium, and a magnetic field generation during recording. Magnetic field modulating means for changing the intensity of the generated magnetic field of the means in accordance with the recorded information, and making the intensity of the generated magnetic field of the magnetic field generating means constant during erasing, and returning the magnetization state of the magnetic thin film to the demagnetized state. A magneto-optical recording / reproducing / erasing apparatus characterized by the above-mentioned.