JPH01178107A - Magnetic field device for magneto-optical disk - Google Patents

Abstract

PURPOSE:To attain high speed switching wit a large magnetic field by providing a 2nd coil generating the same direction of magnetic field to that of a 1st coil and passing a laser beam through the center via a hollow and the 1st coil to the arm of the U-shaped multi-layer thin strip high permeability magnetic substance formed through lamination of thin strip high permeability magnetic substances. CONSTITUTION:The hollow part 12 to irradiated a magneto-optical disk 5 with a laser beam L from the outer face of an arm 11A is provided to the tip of the 1st arm 11A of the multi-layer thin strip high permeability magnetic substance 1 and the coil 3 is provided in spiral to the inner circumference of the arm of the hollow 12. Moreover, the coil 2 is provided to the 2nd arm 11B of the multi-layer thin strip high permeability substance 1, the coils 2, 3 are excited by a magnetic field generating current modulation circuit 4 and connected to generate a magnetic field perpendicularly to the magneto-optical disk 5 and in the same direction at the same time. Thus, high speed switching with a large magnetic field is attained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magnetic field applying device for a magneto-optical disk.

[Conventional technology]

In conventional magnetic field application devices for magneto-optical disks, when erasing recorded information on a magneto-optical disk, an external magnetic field is applied with the opposite polarity to that during recording, and a laser beam is applied to the recording medium with the same intensity as during recording. Uniform irradiation, so-called -batch erasure, is performed. That is, the magnetization state of the recording medium is returned to the initial state before recording by applying an external magnetic field.

Here, as the external magnetic field applying means, there are, for example, a method using an air-core coil, a method using an electromagnet, or a method using a permanent magnet.

In this magnetic field applying means, an applied magnetic field of several hundreds of steps or more is usually required during recording and erasing, so when an air-core coil is used, the coil becomes large.
Along with this, there is a drawback that the magnetic field switching speed becomes slow and the required applied magnetic field cannot be obtained unless the distance between the recording medium and the coil is made sufficiently close.

Also, when using an electromagnet, the magnetic field applying means becomes larger,
The disadvantage is that 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 applying means, the aforementioned batch erasing method is used for erasing, and when recording, laser power is applied while a constant magnetic field is applied. A method of high-speed modulation is used.

[Problem that the invention seeks to solve]

The above-mentioned conventional magnetic field applying device for magneto-optical disks has a slow magnetic field switching speed and uses a batch erasing method, so it has a so-called override function that overwrites new information at high speed on a magneto-optical disk on which information has already been recorded. The problem is that it is difficult to provide

An object of the present invention is to provide a magnetic field application device for a magneto-optical disk that can switch a large magnetic field at high speed and has an override function.

[Means for solving problems]

A magnetic field applying device for a magneto-optical disk according to the present invention includes first and second arm portions that are folded back outside the periphery of a magneto-optical disk, and whose inner surfaces face the upper and lower surfaces of the magneto-optical disk, respectively. A U-shaped multi-layer thin strip high permeability magnetic material laminated with a thin strip high permeability magnetic material, and a U-shaped multilayer thin strip high permeability magnetic material laminated, and a U-shaped multilayer thin strip high permeability magnetic material laminated, and a U-shaped multilayer thin strip high permeability magnetic material laminated, and a a hollow portion for irradiating the magneto-optical disk with a laser beam; a first coil provided in at least one of the first and second arm portions and generating a predetermined magnetic field toward the magneto-optical disk; A second coil is provided around the inner surface of the arm portion of the hollow portion and generates a magnetic field simultaneously and in the same direction as the first coil.

〔Example〕

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

FIG. 1 is a perspective view showing an embodiment of the present invention.

The multilayer ribbon high permeability magnetic material 1 is folded back outside the peripheral portion of the magneto-optical disk 5, and has first and second arm portions 114.1 whose inner surfaces face the upper and lower surfaces of the magneto-optical disk 5, respectively.
1B, and is formed into a U-shape by laminating and bonding about 30 thin strips of high permeability magnetic material.

Here, the ribbon high permeability magnetic material is made of ferrite (MnZn) with a thickness of 30 μm and a length of about 20 cm.

NiZn, etc.), permalloy (NiFu), sendust, amorphous (CoZr, FeCoZr, CoNb,
CoTa, CoHf, etc.), iron core, etc. are used.

A hollow portion 12 is provided at the tip of the first arm portion 11A of the multilayer ribbon high permeability magnetic material 1 for irradiating the laser beam L onto the magneto-optical disk 5 from the outer surface side of the arm portion 11A.
A spiral coil 3 is provided around the inner surface of the arm portion of the hollow portion 12. The inner diameters of the hollow portion 12 and the coil 3 are set to a size that allows the laser beam to pass therethrough and allows the lens to move in the track direction by tracking.

Further, the second arm portion 11 of the multilayer ribbon high permeability magnetic material 1
A is provided with a coil 2, and these coils 2.3
are driven by a magnetic field generation current modulation circuit 4 and are connected perpendicularly to the magneto-optical disk 5 so as to generate magnetic fields simultaneously and in the same direction.

The wire diameter of these coils 2.3 is, for example, 150 μm, and the appropriate driving current is several 10 to several 100 mA.

With the magnetic field applying means configured in this way, the magnetic field can be focused, and the inductance of the winding can be reduced to 1 μm.
Since it is easy to make the magnetic field less than H, a magnetic field of several hundred oersted can be easily switched at a high speed of several MHz at a position several mm away from the inner surface of the multilayer ribbon high permeability magnetic material l.

FIG. 2 is a block diagram of the peripheral system of a magneto-optical recording and reproducing apparatus to which the embodiment of FIG. I did it.

In FIGS. 1 and 2, the output current (1) of the magnetic field generation current modulation circuit 4 flows through the coils 2 and 3, and upward and downward magnetic fields are alternately applied to the magnetic medium 52 of the magneto-optical disk 5.

The magneto-optical head 7 is the same as the conventional one and has the following configuration.

71 is a linearly polarized laser light source, for example, a semiconductor laser is used. 73A to 73c are beam splitters. A condensing lens 72 for the laser beam L is supported by an actuator 72A. The focus error and tracking error signals are input to the servo control circuits 8A and 8B by the respective light receiving elements 75B and 75c for detecting fourth error signals, respectively, and become servo signals, which are fed back to the actuator 72B. be done.

After passing through the polarizing filter 74, the reproduced signal is detected by the reproduced signal light receiving element 75A, and then sent to the reproduced signal amplification circuit 9.
is amplified by A Durham Thomson prism was used as the polarizing filter 74, and a PIN photodiode was used as the light receiving element 75A for detecting the reproduced signal.

A laser light source modulation circuit 6 is used to modulate the laser light source 71, and the power of the laser light is modulated during recording, erasing, and reproduction.

As the magneto-optical disk 5, a TbFeCo film was further formed to a thickness of 800 mm on SiN formed by sputtering on a plastic substrate 51 with a diameter of 120 mm.
Do not use a disk in which SiN is further formed on the FeCo film.
A trench of 700 m and depth was formed and used as a so-called pre-group substrate.

FIGS. 3(a) to 3(c) show waveform diagrams in the recording operation mode.

Constant strength P that can raise the recording medium above the Curie temperature
By passing a modulation current IA as shown in FIG. 3(b) through the coils 2 and 3 for applying an external magnetic field while irradiating a laser beam of During the cooling process accompanying the running of the medium, a recording magnetization state as shown in FIG. 3(c) is realized in accordance with the direction of the applied magnetic field.

First, while irradiating the laser beam L with a constant intensity of 4 mW onto the 5 surface of the magneto-optical disk at a linear velocity of 9 m/sec, an IMH was applied to the coil 2°3 of the external magnetic field applying means.
When a modulated IA lightning current of 200 mA was applied at Z, good recording was achieved. When a recording magnetic field of Q and 5 MHz was newly applied to this recording track under the same conditions, recording corresponding to this recording magnetic field was possible, and no residual trace of the previously recorded signal was observed.

〔Effect of the invention〕

As explained above, the present invention provides a first disk whose inner surface faces each of the upper and lower surfaces of the magneto-optical disk. The laser beam passes through the center of the arm of the second arm, which is made of a U-shaped multilayer thin ribbon high permeability magnetic material, through the first coil and the hollow part. However, by providing a second coil that generates a magnetic field in the same direction as the first coil, the magnetic flux utilization efficiency is high and the inductance can be reduced, allowing high-speed switching of large magnetic fields and an override function. There is an effect that can be used.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the present invention, and FIG. 2 is a perspective view showing one embodiment of the present invention.
FIG. 3 is a block diagram of a peripheral system of a magneto-optical recording/reproducing apparatus to which the embodiment shown in the figure is applied, and FIG. 3 is a waveform diagram in the recording operation mode of the embodiment shown in FIG. DESCRIPTION OF SYMBOLS 1... Multilayer thin ribbon high permeability magnetic material, 2, 3... Coil, 4... Magnetic field generation current modulation circuit, 5... Magneto-optical disc, 6... Laser light source modulation circuit, 7. ...Magneto-optical head, 8A, 8B... Servo control circuit, 9...
・Amplifier circuit, IIA, IIB...Arm section, 12...
- Hollow part, 51... Substrate, 52... Magnetic medium, 71
...Laser light source, 72...Condensing lens, 72A
... Actuator, 73A-73c... Beam splitter, 74... Polarizing filter, 75A-75c...
··Light receiving element.

Claims (1)

[Claims] A U that is folded back outside the periphery of a magneto-optical disk, has first and second arm portions whose inner surfaces face the upper and lower surfaces of the magneto-optical disk, respectively, and has a plurality of laminated thin strips of high permeability magnetic material. a multilayer ribbon high permeability magnetic material having a shape of
and a hollow portion provided at the tip of at least one of the second arm portions for irradiating the magneto-optical disk with a laser beam from the outer surface side of the arm portion, and at least one of the first and second arm portions. a first coil that is provided in the magneto-optical disk and generates a predetermined magnetic field with respect to the magneto-optical disk;
A magnetic field applying device for a magneto-optical disk, comprising a second coil that is provided around the inner surface of the arm portion of the hollow portion and generates a magnetic field simultaneously and in the same direction as the first coil.