JPS63144401A - Magnetic field impressing device for magneto-optical disk - Google Patents

Abstract

PURPOSE:To execute a high speed switching of a large magnetic field by providing two high magnetic permeability magnetic materials to which a core winding for allowing the same current flow has been performed, so as to be opposed to both faces of a magneto-optical disk, and forming one of the high magnetic permeability magnetic materials to a hollow in a shape of a concentric circle. CONSTITUTION:The titled device is constituted of a winding 5, a cylindrical high magnetic permeability magnetic material 4 in which a laser beam can pass through its hollow, and also, to which the winding 5 has been wound, a winding 23, a columnar high magnetic permeability magnetic material 22 which is installed opposingly by inserting and holding a magneto-optical disk, and to which the winding 23 has been wound, and a magnetic field generating current modulation circuit 20 for allowing the same current to flow to the windings 5, 23. By allowing a current to flow to the windings 5, 23 by this magnetic field generating current modulation circuit 20, an impressed magnetic field in the vertical direction of a recording medium is given. As for the high magnetic permeability magnetic material 22, soft ferrite such as an NiFe alloy or NiZn ferrite or MnZn ferrite, etc., whose thickness is several millimeters and whose length is several millimeter - several tens of millimeters is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic field application device for an optical disk that can switch a large magnetic field at high speed.

[Conventional technology]

For example, 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. Batch deletion is performed. In this manner, the magnetization state of the recording medium returns to the initial state before recording by applying an external magnetic field.

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

[Problem that the invention seeks to solve]

In the magnetic field applying means described above, an applied magnetic field of several hundred oersted or more is usually required during recording and erasing.
When using an air-core coil, the coil becomes larger, which slows down the magnetic field switching speed, and the disadvantage is that the required applied magnetic field cannot be obtained unless the distance between the recording medium and the coil is sufficiently close. there were. Furthermore, when an electromagnet is used, the magnetic field applying means is large and the magnetic field switching speed is slow. Furthermore, when permanent magnets are used, a complicated mechanism is required to switch the magnetic field using a mechanical drive means, and the magnetic field switching speed is also slow in this case. As mentioned above, since the magnetic field switching speed is slow with any conventional external magnetic field application means, the aforementioned batch erasing method is used for erasing, and when recording, the laser power is increased at high speed while a constant magnetic field is applied. A modulation method was used. 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.

SUMMARY OF THE INVENTION An 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 in order to solve these conventional problems.

[Means for solving problems]

In order to achieve the above object, the magnetic field application device for a magneto-optical disk has two high permeability magnetic bodies facing each side of the magneto-optical disk each having a core winding that conducts the same current. The high magnetic permeability body is concentrically hollow.

Here, ferrite (MnZn, N
iZn, etc.), permalloy (NiFe), amorphous (CoZr, CoZrNb, CoTa, CoHf, etc.)
, iron core, etc. Further, one of the high magnetic permeability magnetic bodies having a concentric hollow is set between the laser condensing lens and the magneto-optical medium, and the inner diameter of the hollow is such that the laser beam can pass through the lens and the lens is directed in the track direction by tracking. Set the size so that it can be moved.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a perspective view showing an example of the configuration of the magnetic field applying means of the present invention, and the present invention will be explained in detail using this diagram.

The magnetic field applying device for a magneto-optical disk of the present invention includes a winding 5, a cylindrical optically permeable magnetic body 4 through which a laser beam can pass through a hollow space and around which the winding 5 is wound, and the winding 23. A cylindrical high permeability magnetic body 22 placed facing each other with a magneto-optical disk in between and around which the winding 23 is wound, and the windings 5 and 2.
3 and a magnetic field generation current modulation circuit 20 that flows the same current. This magnetic field generation current modulation circuit 20 applies a magnetic field in the direction perpendicular to the recording medium by passing current through the windings 5 and 23. Here, as the high magnetic permeability magnetic material 22, a soft ferrite such as an iFe alloy or NiZn ferrite or MnZn ferrite with a thickness of several millimeters and a length of several millimeters to several tens of millimeters is used. Further, as the winding wire, a copper wire having a wire diameter of several tens of microns to several hundred microns is used, the number of turns is several tens of turns, and the appropriate current value is several tens to several hundred milliamperes.

With the magnetic field applying means configured in this manner, it is easy to reduce the inductance L of the winding to 10 μH or less, so that high-speed switching of a magnetic field of several hundred oersted order to several megahertz order is possible with high magnetic permeability. This can be easily achieved at a position several millimeters away from the end face of the magnetic material. Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

Next, an example in which the present invention is applied to a magneto-optical recording/reproducing device will be described in detail.

The magneto-optical recording and reproducing apparatus shown in FIG. 2 was used to record, reproduce, and erase information on the magneto-optical disk. As the external application means, the one shown in FIG. 1 was used. In FIG. 2, external application means (i.e., high permeability magnetic material 4,
22 and the respective combinations of windings 5 and 23 are arranged on both sides of the recording medium to face each other, and upward and downward magnetic fields are alternately applied to the recording medium by the windings 5 and 23. Here, 20 is a magnetic field generation current modulation circuit. The magneto-optical recording head 3 is the same as the conventional one, and has the following configuration.

6 is a linearly polarized laser light source, for example, a semiconductor laser is used. 7, 8, and 9 are beam splitters, and a laser beam focusing lens 10 is supported by an actuator 11. The focus error signal and the tracking error signal are sent to the servo control circuit 1 by focus error detection light receiving elements 12 and 13, respectively.
4 and 15, becomes a servo signal, and is fed back to the actuator 11. After passing through the polarizing filter 16 , the reproduced signal is detected by the reproduced signal light receiving element 17 and amplified by the reproduced signal amplification circuit 18 .

A Durham Thomson prism was used as the polarizing filter 16, and a PIN photodiode was used as the light receiving element 17 for detecting a reproduced signal. A laser light source modulation circuit 19 is used to modulate the laser light source 6, and the power of the laser light is modulated during recording, erasing, and reproduction, and the high permeability magnetic material 4 is modulated.
The recording medium is irradiated through the hollow part 25 of. The magneto-optical disk used was a disk in which a TbFe film was formed to a thickness of 800 angstroms by sputtering on a plastic substrate having a diameter of 1201 mm. The board has a width of 0 in advance.
．． 8 μm.

A so-called pre-group substrate in which a groove of 2.5 μm and a depth of 700 angstroms was formed was used.

FIGS. 3(a) to 3(c) show recording operation mode diagrams.
The recording medium is a magneto-optical disk 1 on which a magnetic thin film 2 is sputtered.
While irradiating the magnetic thin film 2 with a laser beam of a constant intensity that can raise the temperature above one Curie temperature, the winding 5.23 for applying an external magnetic field is heated to obtain the recording power shown in FIG. 3(a). By passing a modulated current as shown in Fig. 3(b), an external magnetic field corresponding to the recording pattern is applied, and in the cooling process accompanying the running of the recording medium, an external magnetic field is applied corresponding to the direction of the applied magnetic field as shown in Fig. 3(b). A recorded magnetization state as shown in C) is realized. 4 on the disk surface at a linear velocity of 9 m/sec
When a modulated current of 200 mA was passed through the windings 5 and 23 of the external magnetic field applying means while irradiating the laser beam with a constant intensity of mW, good recording was achieved. When a recording magnetic field of 15 MHz was newly applied on this recording track under the same conditions, recording corresponding to this recording magnetic field was completed. No trace of the previously recorded signal was observed.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide an external magnetic field application device for a magneto-optical disk that is capable of high-speed switching of a large magnetic field, and in the magneto-optical recording reproduction erasing method, it is possible to directly apply a desired magnetic field without requiring the conventional batch erasing. This has the effect of realizing override performance that allows recording of .

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing an example of the configuration when the present invention is applied to a magneto-optical recording/reproducing device, and FIGS. c) is a chart showing recording power, modulation current, and recording magnetization state corresponding to time. In the figure, 1 is a magneto-optical disk, 2 is a magnetic thin film, 3 is a magneto-optical recording head, 6 is a laser light source, 7, 8 and 9 are beam splitters, 10 is a laser beam focusing lens, 11 is an actuator, 12 and 13 are light receiving elements for focus error detection, 14 and 15 are servo control circuits, 1
6 is a polarizing filter, 17 is a light receiving element for reproduced signals, 18 is an amplifier circuit, 1 is a laser light source modulation circuit, 20 is a magnetic field generation current modulation circuit, 25 is a hollow part, 4 and 22 are high permeability magnetic materials, 5・23 shows the winding wires respectively. (c) [[↑1↑↓↑↓↑, 1

Claims (1)

[Claims] Two high magnetic permeability magnetic bodies each having a winding that conducts the same current are provided on opposite sides of the magneto-optical disk, and one of the high magnetic permeability bodies is cylindrical and hollow. A magnetic field application device for a magneto-optical disk characterized by: