JPH01224902A - Magnetic field impressing electromagnet for magneto-optical disk - Google Patents

Abstract

PURPOSE:To attain the high-speed switching of a large magnetic field by using a unit of high permeability magnetic substance having plural parallel coils on one surface of a magneto-optical disk. CONSTITUTION:In the middle of a high permeability magnetic substance 1, a first parallel coil group 2 obtained by connecting in parallel, the coils in an (n) number to generate the magnetic field in the same direction, and a second parallel coil group 3 obtained by connecting, in parallel, the coils in the (n) number to generate the magnetic field in the opposite direction are provided. One sides of the terminals of the first and second coil groups 2 and 3 are connected to be the electromagnetic having the three terminals as a whole, and the inductance of the coil is drastically reduced. Thus, since the rise time of a recording current becomes smaller, the switching speed of the magnetic field can be made faster.

Description

[Detailed description of the invention] [Industrial application field] 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 the opposite polarity to that during recording, and a laser beam is uniformly irradiated onto the recording medium with the same intensity as during recording.
So-called -batch deletion is performed. That is, by applying an external magnetic field, the magnetization state of the recording medium is returned to the initial state before recording.

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

[Problem to be solved by the invention]

In the above-mentioned magnetic field applying means, an applied magnetic field of several hundred or more steps is usually required during recording and erasing, so when an air-core coil is used, the coil becomes large, and along with this, the magnetic field switching becomes difficult. This has the disadvantage that the speed is slow and that the desired applied magnetic field cannot be obtained unless the distance between the recording medium and the coil is sufficiently close. Further, when an electromagnet is used, the magnetic field applying means is large in size, and the magnetic field switching speed is slow due to the large inductance of the coil. Furthermore, when using permanent magnets, a complicated mechanism is required to switch the magnetic field using a mechanical drive means, and in this case as well, the magnetic field switching speed is slow. , since the magnetic field switching speed is slow with any conventional external magnetic field application means,
For erasing, the aforementioned batch erasing method is used, and for recording, a method is used in which laser power is modulated at high speed while a constant magnetic field is applied. That is, the conventional apparatus has a problem in that it is difficult to provide a so-called override function for rapidly overwriting new information on already recorded information.

The purpose of the present invention is to solve such conventional problems,
The object of the present invention is to provide a novel means for applying an external magnetic field that enables high-speed switching of a large magnetic field.

[Means to solve the problem]

The magnetic field applying electromagnet for a magneto-optical disk of the present invention includes a high magnetic permeability magnetic strip placed on one side of a magneto-optical disk, and n pieces of magnetic strip that are provided in the middle of this high permeability magnetic strip and generate a magnetic field in the same direction. a first parallel coil group in which n coils are electrically connected in parallel; and a second parallel coil group in which n coils that generate a magnetic field in the opposite direction to the first parallel coil group are electrically connected in parallel.
an electromagnet having three terminals as a whole by connecting one terminal of the first parallel coil group and the second parallel coil group; and an electromagnet that is connected to the surface of the magneto-optical disk. It is constructed by having a piezoelectric element that is moved perpendicularly to the piezoelectric element.

Here, the high permeability magnetic material is ferrite (MnZn, Ni
Zn, etc.), permalloy (NiFe), sendust, amorphous (CoZr, CoZr, FeCoZr, Co
Nb, CoTa, CoHf, etc.), iron core, etc. can be considered. Further, the open magnetic path portion of the high permeability magnetic material is provided to face the laser condensing lens via the magneto-optical medium. Furthermore, the first and second n coils are each electrically connected in parallel, and the first and second coil groups are connected at one terminal, thereby forming a three-terminal electromagnet as a whole. The inductance of the coils is significantly reduced due to their parallel connection. Therefore, since the inductance is small, the rise time of the recording current is shortened, so that the switching speed of the magnetic field can be significantly increased.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of an embodiment of the present invention. In FIG. A high magnetic permeability magnetic body 1 having a path is provided, and a first parallel coil group 2 and a second coil group 3 electrically connected in parallel are provided in the middle of this high magnetic permeability magnetic body 1. The first parallel coil group and the second parallel coil group are configured with one terminal connected to each other. Recording current is alternately supplied from the electromagnet drive circuit 4 to the first parallel coil and the second parallel coil. The high permeability magnetic material 1 is supported by a piezoelectric element 5, which is driven by a piezoelectric element drive circuit 6. By driving the piezoelectric element 5, a gap l is always maintained between the magnetic film surface of the magneto-optical disk. The high magnetic permeability magnetic body 1 supported by the magneto-optical disk can be separated from the magnetic film surface of the magneto-optical disk to facilitate attachment and detachment of the magneto-optical disk.

Figure 2 is a circuit diagram of Figure 1, showing a first parallel coil group 2 and a second parallel coil group 3, each made of a plurality of insulated conductors, and an electromagnet drive circuit that drives these parallel coil groups. 4 is shown. From the electromagnet drive circuit 4 to the first
By alternately passing current through the second parallel coil group 2.3, an applied magnetic field with a perpendicular component is applied to the recording medium. The high permeability magnetic material 1 was made of a material having a thickness of 31 m1 and a magnetic path length (gap) of approximately 1.5 m, and the first and second coil groups used had wire diameters of 150 .mu.m. In addition, the current value ranges from several tens of mA to 1. OA is appropriate. In the magnetic field applying means configured in this way, since the coils are electrically connected in parallel, it is easy to reduce the inductance L of the coil to 1 μH or less. At the position, several hundred
The Oersted magnetic field can be easily switched at a high speed of several MHz.

FIG. 3 is a block diagram of a magneto-optical recording and reproducing apparatus in which a peripheral system is added to the embodiment shown in FIG. 1. This apparatus was used to perform recording, reproduction and erasure on a magneto-optical disk. In FIG. 3, the output current of the electromagnet drive circuit 4 is
upward and downward magnetic fields are alternately applied to the recording medium constituted by the magneto-optical disk magnetic film 2.

The magneto-optical recording head 31 is the same as the conventional one, and has the following configuration. 32 is a linearly polarized laser light source, for example, a semiconductor laser is used. 33, 34.
35 is a beam splitter. The laser beam focusing lens 36 is supported by an actuator 37. The focus error signal and the tracking error signal are detected by the focus error signal detection light receiving element 38. The tracking error signal detection light receiving element 39 inputs the tracking error signal to the servo control circuit 40 , 41 , becomes a servo signal, and feeds it back to the actuator 37 . After passing through the polarizing filter 42 , the reproduced signal is detected by the reproduced signal light receiving element 43 and amplified by the reproduced signal amplification circuit 44 . A Durham Thomson prism is used as the polarizing filter 42, and a PIN is used as the light receiving element 43 for detecting the reproduced signal.
A photodiode was used. A laser light source modulation circuit 45 is used to modulate the laser light source 32, and when recording, erasing,
The power of the laser beam is modulated in accordance with the reproduction time.

As a magneto-optical disk, Tb
A disk was used in which a FeCo film was formed to a thickness of 800 angstroms and SiN was formed on the TbFeCo film. The substrate used was a so-called pre-group substrate in which grooves with a track pitch of 1.6 μm and a depth of 700 angstroms were formed in advance.

FIGS. 4(a) to 4(C) are recording operation mode diagrams. While irradiating a laser beam with a constant intensity that can raise the recording medium above the Curie temperature, modulation as shown in Figure 4(b) is applied to the first and second parallel coil groups 2°3 for applying an external magnetic field. By passing a current, an external magnetic field corresponding to the recording pattern is applied, and during the cooling process as the recording medium runs, the recording magnetization state as shown in FIG. 4(C) is changed according to the direction of the applied magnetic field. Realized. First, while irradiating a constant intensity laser beam of 10 mW onto the disk surface at a linear velocity of 9 m/sec, the coil 2.3 of the external magnetic field applying means was applied with IMHz.
Good recording was achieved when a modulation current of 200 mA was applied. When a recording magnetic field of 0.5 MHz was newly applied to this recording track under the same conditions, recording corresponding to this recording magnetic field was achieved, and the previously recorded signal remained for 28 d.
B, and it was found to be sufficiently practical.

〔Effect of the invention〕

As described above, according to the present invention, since an integrated high permeability magnetic material having multiple parallel coils is used on one side of the magneto-optical disk, the inductance of the coil can be reduced and high-speed switching of large magnetic fields can be achieved. It is possible to provide a magnetic field applying electromagnet for a magneto-optical disk that is possible and has high magnetic flux utilization efficiency.

Therefore, the magneto-optical recording and reproducing method has the effect of realizing override performance that allows desired recording to be performed directly without requiring the conventional batch erasing. Furthermore, 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 using a piezoelectric element, which has the effect of making it easier to handle the magneto-optical disk.

[Brief explanation of the drawing]

1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a circuit diagram of FIG. 1, FIG. 3 is a configuration diagram of the embodiment of FIG. 1 applied to a magneto-optical disk device, and FIG. The figure is an operational mode diagram of the recording of FIG. 3. DESCRIPTION OF SYMBOLS 1... High permeability magnetic material, 2... First parallel coil group, 3... Second parallel coil group, 4... Electromagnet drive circuit, 5... Piezoelectric element, 6...・Piezoelectric element drive circuit, 1
DESCRIPTION OF SYMBOLS 1... Optical disk substrate, 12... Optical disk magnetic medium, 31... Magneto-optical recording head, 32... Laser light source, 33.34.35... Beam splitter, 36
... Laser light beam condensing 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... Polarizing filter, 43... Light receiving element for detecting reproduced signal, 44... Amplifying circuit, 45... Laser light source modulation circuit.

Claims (1)

[Claims] A high permeability magnetic strip placed on one side of the magneto-optical disk and n coils installed in the middle of this high permeability magnetic material and generating magnetic fields in the same direction are electrically connected in parallel. The first parallel coil group consists of one parallel coil group and a second parallel coil group in which n coils that generate a magnetic field in the opposite direction to the first parallel coil group are electrically connected in parallel. It is characterized by having an electromagnet that has three terminals as a whole by connecting one terminal of the coil group and the second parallel coil group, and a piezoelectric element that moves this electromagnet perpendicularly to the surface of the magneto-optical disk. Magnetic field applying electromagnet for magneto-optical disks.