JP2811673B2 - Magnetic field applying electromagnet for magneto-optical disk - Google Patents

Description

The present invention relates to a magnetic field applying electromagnet for a magneto-optical disk.

[Conventional technology]

When erasing recorded information in conventional magneto-optical recording, an external magnetic field is applied with a polarity opposite to that during recording, and a laser light beam is uniformly irradiated on the recording medium at the same intensity as during recording, so-called batch. Erasure is taking place. That is, the magnetization state of the recording medium is returned to the initial state before recording by applying an external magnetic field.

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

[Problems to be solved by the invention]

In the above-described magnetic field applying means, an applied magnetic field of several hundred Oersted or more is usually required at the time of recording and erasing. Therefore, when an air-core coil is used, the coil becomes large, and the magnetic field switching speed is accordingly increased. Slows down,
If the distance between the recording medium and the coil is not sufficiently reduced, a required applied magnetic field cannot be obtained. Also, when an electromagnet is used, the size of the magnetic field applying means is increased and the inductance of the coil is large, so that the magnetic field switching speed is slow. Further, when a permanent magnet is used, a complicated mechanism is required for switching the magnetic field using a mechanical driving means, and the magnetic field switching speed is also slow in this case. As described above, since the magnetic field switching speed is slow by any of the conventional external magnetic field applying means, the above-described batch erasing method is used for erasing, and when recording, the laser power is increased during application of a constant magnetic field. A modulation method is used. That is, the conventional apparatus has a problem that it is difficult to provide a so-called overwrite function for overwriting already recorded information with new information at a high speed.

An object of the present invention is to solve such a conventional problem and to provide a novel external magnetic field applying unit that enables high-speed switching of a large magnetic field.

[Means for solving the problem]

A magnetic field applying electromagnet for a magneto-optical disk according to the present invention is provided on a high magnetic permeability magnetic body disposed on one surface of a magneto-optical disk and a part of the high magnetic permeability magnetic body so as to generate a magnetic field in the same direction. a first parallel coil group in which n coils are electrically connected in parallel, and a direction in which one end is connected to the first parallel coil group and a magnetic field generated by the first parallel coil group is opposite to the first parallel coil group. And a second parallel coil group in which n coils are electrically connected in parallel so as to generate a magnetic field of one end, one end of the first parallel coil group and one end of the second parallel coil group. And an electromagnet having three terminals as a whole, and a piezoelectric element for supporting the electromagnet at a predetermined interval with respect to the surface of the magneto-optical disk and for vertically moving the electromagnet. You.

Here, as the high magnetic permeability magnetic material, ferrite (MnZn, NiZn, etc.), permalloy (NiFe), sendust, amorphous (CoZr, CoZr, FeCoZr, CoNb, CoTa, CoHf, etc.), iron core, and the like can be considered. The open magnetic path portion of the high-permeability magnetic material is provided to face the laser focusing lens via the magneto-optical medium. Furthermore, the first and second n coils are electrically connected in parallel, respectively, and one terminal of the first and second coil groups is connected to form a three-terminal electromagnet as a whole. The inductance of the coil is greatly reduced due to the parallel connection. Therefore, since the rise time of the recording current is reduced due to the small inductance, the switching speed of the magnetic field can be greatly increased.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of one embodiment of the present invention. In the drawing, a magnetic field applying electromagnet for a magneto-optical disk is provided with a high-permeability magnetic body 1 having an open magnetic path facing a magneto-optical disk magnetic film 8 provided on the back surface of a magneto-optical disk substrate 7. A first parallel coil group 2 and a second coil group 3 electrically connected in parallel are provided in the middle of the magnetic susceptibility magnetic body 1.
And the second parallel coil group are configured such that one terminal is connected. The recording current is alternately supplied from the electromagnet drive circuit 4 to the first parallel coil and the second parallel coil. Further, the high-permeability magnetic body 1 is supported by the piezoelectric element 5, and the piezoelectric element 5 is driven by the piezoelectric element driving circuit 6.
The high-permeability magnetic body 1 supported on the magnetic film surface of the magneto-optical disk with the gap 1 kept therebetween can be separated from the magnetic film surface of the magneto-optical disk to facilitate mounting and dismounting of the magneto-optical disk.

FIG. 2 is a circuit diagram of FIG. 1, in which a first parallel coil group 2 and a second parallel coil group 3 each formed by a plurality of insulated conductors, and an electromagnet drive circuit for driving these parallel coil groups 4 is shown. By applying a current alternately from the electromagnet drive circuit 4 to the first and second parallel coil groups 2 and 3, an applied magnetic field of a perpendicular component is applied to the recording medium. The high-permeability magnetic material 1 used had a thickness of 3 mm and a magnetic open circuit length (gap) of about 5 mm. The first and second coil groups used had a wire diameter of 150 μm. Further, several tens mA to 1.0 A is appropriate as the current value. In the magnetic field applying means configured as described above, since the coil is electrically connected in parallel, the inductance L of the coil is 1 μH
Since it is easy to make the following, the magnetic field of several hundred Oersteds can be easily switched at a high speed of several MHz at a position several mm away from the end face of the high magnetic permeability magnetic body.

FIG. 3 is a block diagram of a magneto-optical recording / reproducing apparatus in which a peripheral system is added to the embodiment of FIG. In FIG. 3, the output current of the electromagnet drive circuit 4 flows through the first parallel coil group 2 and the second parallel coil group 3, and an upward and downward magnetic field alternates on the recording medium constituted by the magneto-optical disk magnetic film 8. Is applied to

The magneto-optical recording head 31 is equivalent to a conventional one, and has the following configuration. Reference numeral 32 denotes a linearly polarized laser light source, for example, a semiconductor laser. 33, 34 and 35 are beam splitters. The laser beam focusing lens 36 is supported by an actuator 37. The focus error signal and the tracking error signal are input to the servo control circuits 40 and 41 by the light receiving element 38 for detecting a focus error signal and the light receiving element 39 for detecting a tracking error signal, respectively, become servo signals, and are fed back to the actuator 37. After the reproduction signal passes through the polarizing filter 42,
It is detected by the reproduction signal light receiving element 43 and amplified by the reproduction signal amplifier circuit 44. A Gram-Thompson prism is used as the polarizing filter 42, and a light-receiving element for detecting a reproduced signal.
As PIN 43, a PIN photodiode was used. Laser light source 3
The laser light source modulation circuit 45 is used for the modulation of 2, and the power of the laser light is modulated at the time of recording, erasing, and reproducing.

TbFeCo on SiN formed by sputtering on a 120 mm diameter plastic substrate as a magneto-optical disk
A disk having a thickness of 800 Å and a SiN film formed on the TbFeCo film was used. A so-called pre-groove substrate in which a groove having a track pitch of 1.6 μm and a depth of 700 Å was formed in advance was used.

4A to 4C are operation mode diagrams of recording.
While irradiating the recording medium with a laser beam of a constant intensity capable of raising the temperature above the Curie temperature, a first
By applying a modulation current as shown in FIG. 4 (b) to the parallel coil groups 2 and 3 of the second and the third, an external magnetic field corresponding to the recording pattern is applied, and the cooling process accompanying the running of the recording medium is performed. Thus, a recording magnetization state as shown in FIG. 4 (c) is realized corresponding to the direction of the applied magnetic field. First, 200-mA modulated current of 1 MHz was applied to the coils 2 and 3 of the external magnetic field applying means while irradiating a constant intensity laser beam of 10 mW on the disk surface at a linear velocity of 9 m / sec. . When a new recording magnetic field was applied at 0.5 MHz to this recording track under the same conditions, recording corresponding to this recording magnetic field could be performed, and the previously recorded signal had an erasure of 28 dB. Do you get it.

〔The invention's effect〕

As described above, according to the present invention, an integrated high-permeability magnetic material having a plurality of parallel coils is used on one side of a magneto-optical disk, so that the inductance of the coil can be reduced and high-speed switching of a large magnetic field can be achieved. It is possible to provide a magnetic field applying electromagnet for a magneto-optical disk which is possible and has high magnetic flux utilization efficiency. Therefore, the magneto-optical recording / reproducing method has an effect that an overwrite performance capable of directly performing a desired recording can be realized without requiring the conventional batch erasing. Further, since the high-permeability magnetic material is provided only on one side of the magneto-optical disk, the high-permeability magnetic material can be moved by using the piezoelectric element, so that the magneto-optical disk can be easily handled.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a circuit diagram of FIG. 1, FIG. 3 is a block diagram of a case where the embodiment of FIG. 1 is applied to a magneto-optical disk drive, FIG. The figure is a diagram showing the operation mode of the recording shown in FIG. 1. High magnetic permeability magnetic body 2. First parallel coil group 3,
... A second parallel coil group, 4... An electromagnet drive circuit, 5.
... Piezoelectric element, 6 ... Piezoelectric element drive circuit, 11 ... Optical disk substrate, 12 ... Optical disk magnetic medium, 31 ... Magneto-optical recording head, 32 ... Laser light source, 33,34,35 ... Beam splitter, 36: Laser beam focusing lens, 37: Actuator, 38: Light receiving element for focus error signal detection, 39 ... Light receiving element for tracking signal detection, 40, 41 ...
... Servo control circuit, 42 ... Polarization filter, 43 ... Reproduction signal detection light receiving element, 44 ... Amplification circuit, 45 ... Laser light source modulation circuit.

Claims (1)

(57) [Claims] 1. A high-permeability magnetic body disposed on one side of a magneto-optical disk and n coils provided on a part of the high-permeability magnetic body so as to generate a magnetic field in the same direction. A first parallel coil group connected in parallel to the first parallel coil group, and one end connected to the first parallel coil group, and generating a magnetic field in a direction opposite to a magnetic field generated by the first parallel coil group. A second parallel coil group in which n coils are electrically connected in parallel, and one end of the first parallel coil group and one end of the second parallel coil group are connected to form a whole. A magnetic field application for a magneto-optical disk, comprising: an electromagnet having three terminals; and a piezoelectric element that supports the electromagnet at a predetermined distance from the surface of the magneto-optical disk and moves the electromagnet vertically. electromagnet.