JPS62189653A - Photomagnetic recording and reproducing head - Google Patents

Abstract

PURPOSE:To produce a magnetic field vertical to the film surface of a photomagnetic recording medium in a sharp and intensive way in terms of space, by using >=2 pieces of electromagnets contains magnetic cores set opposite to each other as the external magnetic field generating means and conducting the current to the coils so that the same polarities are set opposite to each other. CONSTITUTION:The coils containing magnetic cores, i.e., the electromagnets 20 and 21 are set opposite to each other as the external magnetic field generating means. Here a gap space between both magnets 20 and 21 is decided so that the luminous flux given from an objective lens 9 can pass through said gap. Then the current is conducted to both coils so that the same polarities of both magnets 20 and 21 are set opposite to each other. As a result, a sharp vertical magnetic field is obtained in terms of space between both electrodes 20 and 21. Thus it is possible to produce a magnetic field vertical to the film surface of a photomagnetic recording medium 10 in a sharp and intensive way in terms of space.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magneto-optical recording and reproducing device using a magneto-optical recording medium, and in particular, it compensates for the lack of external magnetic field during recording and erasing, and locally increases the magnetic field. The present invention relates to a magneto-optical recording/reproducing head equipped with external magnetic field generating means having a configuration that allows easy convergence.

[Problem that the invention seeks to solve]

Conventionally, as a recording medium for magneto-optical memory, MnB1.
MnAlGe, PtCo, GdFe,
Materials such as GdCo, TbFe, and GdTbFe are used. FIG. 6 shows the basic structure of a magneto-optical memory, ie, a magneto-optical recording medium, in which such a material is used. Magneto-optical memory uses a thin film as a recording medium for magneto-optical recording as a recording layer on a substrate such as glass or silicon wafer.
For example, it can be formed by a method such as vacuum evaporation or sputtering. As the characteristics of these recording media,
It has characteristics such as having magnetic anisotropy perpendicular to the film surface, and relatively low Curie temperature and magnetic compensation temperature. Since these recording media have perpendicular magnetic anisotropy, information can be recorded using either upward magnetization 3 or downward magnetization 4 perpendicular to the film surface of the recording layer 2 on the substrate 1, as shown in FIG. This is done by writing information in binary form as digital signals of "O" and "l" respectively.As a method of recording information,
For example, apply an external magnetic field perpendicularly to the entire film surface of the recording layer 2 in advance, magnetize the recording layer so that it is magnetized upward, and write "0", and then apply a spot laser beam to the part where "l" is to be written. Irradiate and heat.

The coercive force 1 (c) of the heated minute portion becomes small, and if a weak external magnetic field is applied in the direction of downward magnetization during laser beam irradiation, the magnetization is reversed and "1" is recorded.

In this way, a method is used to form a magnetic recording pattern on the recording layer 2 depending on whether or not to irradiate the laser beam. In addition, as a method of reading information, for example, when the magnetic recording pattern is irradiated with a linearly polarized laser beam, the effect of rotating the plane of polarization of the reflected light or transmitted light (called the magnetic Kerr effect and magnetic Faraday effect, respectively) is known. ), the recording layer 2 has, for example, when using the magnetic Kerr effect, the rotation angle θK of the polarization plane of the reflected light
Taking advantage of the fact that the amount of light differs depending on the direction of recording magnetization, the reflected light is passed through an analyzer before entering the photodetector, and information corresponding to the direction of magnetization is read out as a change in the amount of light. When writing new information to a recording medium on which information has already been recorded, first an external magnetic field smaller than the coercive force Hc of the recording medium is applied perpendicular to the medium surface and a laser beam is applied from the beginning to the end of the recording section of the recording track. is scanned and heated to lower the coercive force Hc of the recording medium and direct all the magnetization of the recording medium in the same direction as the surrounding magnetic field. This corresponds to erasure.

Next, an external magnetic field is applied in the direction opposite to that for erasing, and new information is written using the principle already described.

A major feature of the magneto-optical recording medium is that it can be freely erased and rewritten as described above. Recording this information;
Reproduction and erasing are largely influenced by the action of external magnetic fields.

It is desirable that the external magnetic field be a uniform magnetic field perpendicular to the magneto-optical recording medium, and as a result, the magnetic field strength must be such that the reproduction CN ratio tends to be saturated.

Conventionally, as external magnetic field generating means, methods using permanent magnets and methods using electromagnets can be considered.

The method using permanent magnets has the disadvantage that it is necessary to change the direction of the permanent magnet spatially in order to reverse the direction of the magnetic field between recording and erasing, and a mechanical configuration is required. Additionally, permanent magnets have the disadvantage that the magnetic field strength must be controlled by changing the distance from the magneto-optical recording medium. Furthermore, since permanent magnets always generate a magnetic field, there is a restriction that a magneto-optical recording medium must have a high coercive force Hc. On the other hand,
The method using electromagnets can overcome the drawbacks of permanent magnets. However, in order to generate a magnetic field strength above which the reproduced CN ratio shows a tendency to saturate, a conventional simple electromagnet requires a large size and requires a large current to flow. Furthermore, because conventional simple electromagnets cannot perform high-speed switching operations, they have the disadvantage that they cannot perform overwrite recording, which is done in magnetic recording.

The object of the present invention is to improve the above-mentioned drawbacks, and to provide a magneto-optical recording/reproducing head which is equipped with an external magnetic field generating means capable of generating an external magnetic field with a small current when recording and erasing information, and capable of high-speed switching operation. Our goal is to provide the following.

Solution to Problem c] The present invention provides a magneto-optical recording and reproducing head that uses a laser as a light source and irradiates a light flux emitted from the light source onto the surface of a magneto-optical recording medium to optically record and reproduce information. A magneto-optical recording/reproducing head, characterized in that external magnetic field generating means comprising two or more electromagnets arranged with magnetic poles of the same polarity facing each other so as to surround the light flux is installed on the front surface of the head.

〔Example〕

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

FIG. 1 shows an embodiment of the magneto-optical recording/reproducing head of the present invention. This magneto-optical recording/reproducing head has a structure in which a laser is used as a light source and an electromagnet, which is an external magnetic field generating means according to the present invention, is provided in front of an actuator including an objective lens. However, the optical system for obtaining the control signal for driving the actuator is omitted here.

For example, a semiconductor laser 5 is used as the light source.

The light beam generated by the laser 5 passes through a collimating lens 6 and a beam splitter 7 in this order, and is irradiated onto a magneto-optical recording medium 10 by an objective lens 9 installed on an actuator 8 . Note that the magneto-optical recording medium 10 is formed on a substrate 11 that is transparent to laser. A part of the focused light beam is reflected by the recording medium 10. The reflected light beam is split into two parts by a beam splitter.
The polarization plane of the light beam is rotated by π/4 by the wave plate 12,
The light beam is divided into two by the analyzer 13, and the condensing lens 14.1
5 leads to photodetectors 16 and 17. In this embodiment, an external magnetic field generating means 18 according to the present invention is provided on the front surface of the actuator 8 and has a space (gap interval) for a light beam to pass through. The external magnetic field generated by this external magnetic field generating means includes: (1) the presence of a magnetic field distribution perpendicular to the film surface in the portion of the magneto-optical recording medium 10 that is irradiated with focused light; and (2) the strength of the external magnetic field. It is necessary that the value is larger than that indicating the saturated state of the reproduced CN ratio. An air-core solenoid can be considered as an electromagnet that can achieve these two conditions. However, with air-core solenoids, the strength of the generated magnetic field at small currents is limited.
Therefore, in this embodiment, as an external magnetic field generating means, as shown in FIG.
1 are placed facing each other. In this case, the gap spacing is
It is selected so that the light beam from the objective lens 9 in FIG. 1 can pass therethrough. Then, current is passed through the coils of each electromagnet so that the same polarity faces each other. In this embodiment, it is assumed that the N poles are opposite to each other (and N).

FIG. 3 shows the lines of magnetic force coming out of these two electromagnets 20 and 21. In this way, by arranging the same polarity sides to face each other, as shown in FIG. A magnetic field is obtained. Therefore, it is possible to generate a spatially sharp and strong magnetic field perpendicular to the 1° film surface of the magneto-optical recording medium.

In the above embodiment, two electromagnets were used, but a larger number of electromagnets may be used.

FIG. 5 is a plan view of an external magnetic field generating means using four electromagnets. The four electromagnets 22, 23, 24.degree. 25 are arranged at mutually orthogonal positions so as to surround the passing light beam. Then, current is passed through the coils of these electromagnets so that the magnetic poles of the same polarity face each other. In this embodiment as well, a spatially sharp vertical magnetic field is obtained between these electromagnets. If a large number of electromagnets are used in this way, the current flowing per electromagnet can be reduced to obtain the same magnetic field strength, and high-speed switching operation becomes possible.

〔Effect of the invention〕

As explained above, according to the magneto-optical recording/reproducing head of the present invention, two or more electromagnets with magnetic cores are arranged facing each other as external magnetic field generating means, and current is passed through the coils so that the same polarity faces each other. As a result, it is possible to generate a spatially sharp and strong magnetic field perpendicular to the film surface of the magneto-optical recording medium.

Therefore, it is possible to obtain the magnetic field strength that indicates the saturation tendency of the reproduced CN ratio with a smaller current than with conventional electromagnets. Furthermore, if a large number of opposing electromagnets are used, the current flowing per electromagnet can be reduced, so that high-speed magnetic field switching operation is possible, and overwriting recording can be easily achieved. Furthermore, by providing the external magnetic field generating means in front of the actuator, the magneto-optical recording/reproducing apparatus itself can be made smaller.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the magneto-optical recording/reproducing head of the present invention, FIG. 2 is a diagram showing a first example of opposing electromagnets which are external magnetic field generating means according to the present invention, and FIG. FIG. 2 is a diagram explaining the magnetic field lines generated from the electromagnet shown in FIG. 2. FIG. 4 is a diagram explaining the magnetic field intensity distribution generated from the electromagnet shown in FIG. 2. FIG. 5 is an external magnetic field generating means according to the present invention. FIG. 6 is a plan view of a second example of opposing electromagnets. FIG. 6 is a diagram showing the basic configuration of a magneto-optical recording medium. 5... Semiconductor laser 6... Collimator lens 7... Beam splitter 8... Actuator 9... Objective lens 10... Magneto-optical recording medium 11 ... Substrate 12 ... Half wavelength plate 13 ... Analyzers 14, 15 ... Light-building lenses 16, 17 ... Photodetector 18 ... External magnetic field generating means 20 to 25...electromagnet

Claims (1)

[Claims] (1) In a magneto-optical recording/reproducing head that uses a laser as a light source and condenses and irradiates a light beam emitted from the light source onto the surface of a magneto-optical recording medium to optically record and reproduce information, a light beam of the same polarity surrounds the light beam. 1. A magneto-optical recording/reproducing head characterized in that external magnetic field generating means comprising two or more electromagnets with magnetic poles facing each other is installed on the front surface of the head.