JPH03209650A - Magnetic field impressing electromagnet for magneto-optical information device - Google Patents

Abstract

PURPOSE:To form a magnetic field impressing electromagnetic capable of rapidly switching a large magnetic field by providing one of two opposed high permeability magnetic substances with a hole capable of passing an optical beam and a sheet-like coil to be a winding wound around the through-hole. CONSTITUTION:When currents are allowed to flow from a magnetic field generating current modulating circuit 10 to coils 5, 23, a magnetic field is impressed in the vertical direction of a recording medium 8. For instance, Ni-Fe alloy or the soft ferrite of Ni-Zn ferrite or Mn-Zn ferrite having <=2mm thickness and several mm to several tens mm length is used a the high permeability magnetic substance 1, 3. On the other hand, a copper wire having 10mum to several hundreds mum line diameter is used as the coil 23 and the number of turns of the coil is several tens turns. The coil 5 is formed by pattern plating having a spiral shape. In this case, copper plating is executed and a sheet-like coil can be formed by connecting a lead wire 46. The inductance of the coil is easily set up to 10muH and the magnetic field of several hundreds Oe switched on the position separated from the end face of the magnetic substance by several mm at the high speed of several MHz.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic field applying electromagnet for a magneto-optical information device that can switch a large magnetic field at high speed.

[Prior Art] In conventional magneto-optical recording, first, in order to erase already recorded information, 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. So-called "batch erasing" is performed in which the area is uniformly irradiated. That is, erasure is performed by returning the magnetization state of the recording medium to the initial state before recording by applying an external magnetic field, and then, while applying a magnetic field in the opposite direction to the magnetic field direction of the external magnetization state, the data is modulated according to the recorded information. There is a method in which recording is performed by irradiating a recording medium with a laser beam.

In addition, as an overridable magneto-optical recording method, a magnetic field whose direction changes at high speed at a constant period is applied to the magneto-optical recording medium, and a light beam is irradiated according to the recorded information. There is a method of recording by creating a magnetization pattern in the direction of the magnetic field. In this method, in order to record a faithful magnetization pattern in a recording signal, an external magnetic field applying means that changes the magnetic field direction at a higher speed is required.

Also, by constantly irradiating a magneto-optical recording medium with a laser beam of a constant intensity and simultaneously applying an external magnetic field modulated according to the recording signal, a recording magnetization pattern is created on the recording medium and recording is performed. There is also a method. Also in this method, so-called override is possible because an erasing operation is not required before the recording operation. Also, in this method,
In order to perform recording with greater fidelity to recorded information, it is desirable to provide external magnetic field applying means that can apply a large magnetic field that can be switched at higher speeds.

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

[Problems to be Solved by the Invention] In the magnetic field applying means described above, an applied magnetic field of several hundred or more steps is usually required during recording and erasing, so when the above-mentioned air-core coil is used, the coil is As the size increases, the magnetic field switching speed slows down, and
There is a drawback that the required applied magnetic field cannot be obtained unless the distance between the recording medium and the coil is made sufficiently close.

Further, when an electromagnet is used, the magnetic field applying means becomes large and the magnetic field switching speed becomes 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 described above, since the magnetic field switching speed is slow with any conventional external magnetic field applying means, it is difficult to record a magnetization pattern faithful to the recording signal.

Therefore, when erasing records, the above-mentioned batch erasing method is often used, and when recording, a method of high-speed modulation of laser power while applying a constant magnetic field is often used.

That is, in the conventional apparatus, there is a problem in that it is difficult to provide a so-called override function in which new information is overwritten at high speed 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 the problems of the conventional method.

[Means and Effects for Solving the Problems] The present invention provides, as a means for solving the above-mentioned problems, a magnetic field applying electromagnet that applies a magnetic field to a magneto-optical recording medium, in which windings through which the same current flows, Consisting of two high permeability magnetic bodies that face each other with both sides of the recording medium in between and are reinforced with metal, and a magnetic path of the high permeability magnetic body that magnetically connects the two high permeability magnetic bodies. A magnetic field of a magneto-optical information device, characterized in that one of the two opposing high magnetic permeability magnetic bodies has a through hole through which a light beam passes, and a sheet-like coil as the winding around the through hole. It provides an energizing electromagnet.

Further, the sheet-like coil is formed by depositing one or more layers of a conductive material using a magnetic field applying electromagnet of a magneto-optical information device, and the sheet-like coil is formed by depositing a conductive material in a sheet. The magnetic field applying electromagnet of the magneto-optical information device is characterized in that it is formed by coordinating and fixing in a shape.
This is an attempt to solve the above problem.

According to the present invention, two high magnetic permeability magnetic bodies parallel to the surface of the magneto-optical recording medium of the magnetic path are each reinforced with metal, and as a winding of the high permeability magnetic body having the through hole,
By using a sheet-like coil around the through hole, it is possible to obtain a coil with small inductance, and at the same time, it is possible to apply a large magnetic field to the recording medium.

Here, the high permeability magnetic material is ferrite (MnZn
, NiZn, etc.), permalloy (NiFe), Sendust, amorphous (CoZr, CoZrNb, C
Possible reinforcing metals include non-magnetic materials such as aluminum, titanium, copper, and zinc.

Further, one of the high magnetic permeability magnetic bodies having a concentric through hole is set between the laser focusing lens and the magneto-optical medium,
The inner diameter of the through hole is set to a size that allows the laser beam to pass through and allows the lens to move in the track direction by tracking.

In addition, the material of the sheet-like coil having a spiral pattern formed around this through hole is copper or Ni.
, AI2. Possible materials include Pt, Au, and Fe.

[Examples] Examples of the present invention will be described below with reference to the drawings.

FIGS. 1(a) and 1(b) are configuration diagrams of an embodiment of the present invention.

The magnetic field applying electromagnet of the magneto-optical information device of the present invention has a coil 2
A cylindrical high-permeability magnetic body 2 with a magnet 3 wound thereon, and a magneto-optical disk 8 disposed between the cylindrical high-permeability magnetic body 2 and the magneto-optical disk 8 . Figure 1 (b)
A high permeability magnetic material 1 having a sheet-like coil 5 having a spiral pattern, the top view of which is shown in FIG. Metal reinforcing plate 6 for reinforcing the permeability magnetic bodies 1 and 3
and 7, and a magnetic field generation current modulation circuit 10 that causes the same current to flow through the coils 5 and 23.

The magnetic field generation current modulation circuit 10 applies a magnetic field in the perpendicular direction to the recording medium 8 by passing current through the coils 5 and 23.

Here, the high permeability magnetic bodies 1 and 3 are made of NiFe alloy or NiZ with a thickness of 2 μ or less and a length of several mm'' to several tens of mm.
A soft ferrite such as n-ferrite or MnZn ferrite is used, and the high permeability magnetic body 2 is a cylindrical NiFe alloy or MnZn ferrite soft ferrite with a thickness of several mm, and the high permeability magnetic body 4 is NiFe alloy or soft ferrite such as MnZn ferrite with a thickness of several mm is used. Further, as the coil 23, a copper wire with a wire diameter of several 10 μm to several 100 μm is used,
The number of turns of this is several ten turns.

Furthermore, the coil 5 is made by pattern plating having a spiral shape as shown in FIG. 1(b). In the present invention, as an example, copper plating is performed, and a lead wire 46 is further connected to form a sheet-like coil.

In the case of copper, the appropriate current value is several tens to several hundreds of mA.

The metal reinforcing plates 6 and 7 are provided in order to reduce the inductance caused by the high permeability magnetic bodies 1 and 3 and to reduce the volume thereof (to compensate for the deterioration in mechanical strength caused by the reduction).

With the magnetic field applying means configured in this way, it is easy to reduce the inductance of the coil to 10 μH or less, so a magnetic field of several hundred Oersteds is applied at a frequency of several MHz at a position several meters away from the end face of the high magnetic permeability magnetic material. can be switched at high speeds.

FIG. 2 is a block diagram of a magneto-optical recording/reproducing apparatus in which a peripheral system is added to the embodiment shown in FIG.

In FIG. 2, the output of the magnetic field generation current modulation circuit 10 is:
Flowing through the windings 5 and 23, upward and downward magnetic fields are alternately applied to the recording medium constituted by the magnetic thin film 9 of the magneto-optical disk 8.

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. Focus error and tracking error signals are detected by focus error signal detection light receiving elements 38 and 39, respectively.
The signal is input to the servo control sub-circuits 40 and 41, becomes a servo signal, and is fed back to the actuator 37. After passing through the polarizing filter 42 , the reproduced signal is detected by a reproduced signal detection light receiving element 43 and amplified by a reproduced signal amplification circuit 44 . A Durham Thomson prism was used as the polarizing filter 42, and a PIN photodiode was used as the light receiving element 43 for detecting a reproduced signal. A laser light source modulation circuit 45 is used to modulate the laser light source 32, and the power of the laser light is modulated during recording, erasing, and reproduction.

As the magneto-optical disk 8, a disk was used in which a TbFeCo film was formed to a thickness of 800 angstroms by sputtering on a plastic substrate having a diameter of 120 mm. 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. 3(a) to 3(c) are diagrams for explaining the operation mode during recording of the above-described embodiment.

First, while irradiating a laser beam with a constant intensity that can raise the temperature above the Curie temperature of the recording medium, a modulated current according to the recording signal as shown in FIG. 3(b) is passed through the coils 5 and 23 for applying an external magnetic field. As a result, an external magnetic field corresponding to the recording signal is applied.

During the cooling process accompanying the running of the recording medium, this magnetic field realizes a recording magnetization state as shown in FIG. 3(c) in accordance with the direction of the applied magnetic field, and recording is performed.

In this example, as an experiment, the coils 5 and 2 of the external magnetic field applying means were irradiated with a laser beam of a constant intensity of 4 mW onto the disk surface moving relatively at a linear velocity of 9 m/sec.
When a modulation current of 200 mA was applied to the recording magnetic field at 1 MHz, good recording was achieved. Therefore, a new recording magnetic field of 0.5M was applied on this recording track under the same conditions.
When the magnetic field was applied at Hz, recording corresponding to this recording magnetic field was possible, and there was no trace of the previously recorded signal remaining.

That is, even if overriding was performed without performing a batch erase operation as in the conventional case, good recording could be performed.

[Other Examples] In the above example, an example was described in which the sheet-like coil 5 was formed with high density by pattern plating of copper plating.
A sheet-like coil with higher precision can also be formed by gold plating.

Furthermore, similar effects can be obtained and costs can be reduced by arranging copper wires in a coil shape on a sheet and fixing them with an adhesive or the like.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an external magnetic field applying electromagnet for a magnetic disk that is capable of high-speed switching with a strong magnetic field.

Therefore, the magneto-optical recording/reproducing/erasing method using an electromagnet of the present invention has the effect of realizing the override function that enables direct desired recording without the need for conventional batch erasing, and can realize the recorded information more faithfully. be.

Another effect is that the coil around the through hole at one end of the high permeability magnetic material on the side where the light beam is incident is composed of a sheet-like coil, so the distance from the recording medium can be reduced. , it is possible to downsize the device.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention. FIG. 2 is a configuration diagram when the embodiment of FIG. 1 is applied to a magneto-optical disk device. FIG. 3 is a diagram for explaining the operation of the apparatus of the embodiment shown in FIG. 2 during recording.

Claims (3)

[Claims] (1) In a magnetic field applying electromagnet that applies a magnetic field to a magneto-optical recording medium, two high permeability magnetic bodies are provided with windings that conduct the same current, are opposed to each other with both sides of the recording medium in between, and are reinforced with metal. and a magnetic path of a high permeability magnetic material that magnetically connects the two high permeability magnetic materials, and one of the two opposing high permeability magnetic materials has a through hole through which the light beam passes. . A magnetic field applying electromagnet for a magneto-optical information device, comprising a sheet-like coil as the winding around the through hole. (2) The magnetic field applying electromagnet for a magneto-optical information device according to claim 1, wherein the sheet-like coil is formed by depositing one or more layers of conductive material. (3) Magnetic field application of the magneto-optical information device according to claim 1, wherein the sheet-like coil is formed by arranging and fixing windings of conductive material in a sheet-like manner. electromagnet.