JPH04268225A - Magneto-optical recording medium and recording and reproducing method therefor - Google Patents

Abstract

PURPOSE:To enable recording and reproducing to be conducted with a high density and high speed by providing magneto-optical films consisting of two layers of amorphous alloys consisting of iron-group transition metals and rare earth transition metals having specific different compsns. on a substrate and subjecting two layers of the magneto-optical films to exchange bonding at a specific temp. CONSTITUTION:The reading out film 3 which is an amorphous alloy composed of iron, cobalt and gadolinium and having 150 to 300Angstrom thickness, has >=200 deg.C Curie point, has a low coercive force of <0.5k oersted at 10 to 90 deg.C and has the Fourier magnetism dominant with the iron-group transition metals is formed via a transparent interference film 2 on the substrate 1. The perpendicularly magnetizable writing film 4 which is an amorphous alloy composed of iron, terbium and titanium and having >=350Angstrom thickness, has 110 to 200 deg.C Curie point, has a high coercive force of >=1k oersted at 10 to 90 deg.C and has the Fourier magnetism dominant with the ferrous transition metals is formed thereon. The film 3 and the film 4 are then subjected to the exchange bonding at 10 to 90 deg.C. The recording and reproducing are executed at the high density and high speed in this way.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a magneto-optical recording medium and a method for recording and reproducing the same, particularly a method for recording and reproducing information on a magneto-optical recording medium such as an optical disk that can record and reproduce information at high density and high speed using a focused laser beam. Regarding.

0002

2. Description of the Related Art Generally, a magneto-optical type that utilizes the Kerr effect is used as a rewritable optical recording medium. That is, a perpendicularly magnetizable magneto-optical film made of a magnetic metal material is formed on a substrate, and a focused laser beam is irradiated to heat the irradiated part of the magneto-optical film to near the Curie point. By applying a recording bias magnetic field, information is written by orienting the magnetization of this part in the opposite direction to that of other parts, and information is read by applying linearly polarized focused laser light to the magneto-optical film. By optically detecting the reflected light from there through an analyzer. Since the magneto-optical film has the effect of rotating the plane of polarization of reflected light due to the Kerr effect, by utilizing the fact that the rotation angle θk of the plane of polarization of the reflected light differs depending on the direction of perpendicular magnetization of the magneto-optical film,
Before the reflected light enters the photodetector, it passes through an analyzer, and information corresponding to the direction of magnetization can be read out as a change in the amount of light.

In such a conventional information reading system of magneto-optical recording, the area where the direction of perpendicular magnetization of the magneto-optical film has changed becomes a bright or dark area (hereinafter referred to as a recording mark). Such detection methods include a method using a single photodetector, and a differential detection method in which two photodetectors each receive a beam split into two polarized beams by a polarizing beam splitter and the difference between the outputs is calculated. There are laws etc. At this time, for reproduction identification of digital information, a slice level is provided near the midpoint of the read signal amplitude, and recording mark information is pulsed from the recording mark string. At the same time, peak values are detected corresponding to "0" and "1" of the readout waveform, and patterns of "0" and "1" are determined from the timing relationship between the mark information and the reproduction clock determined by various modulation methods, The information of the source data is being reproduced.

Materials for the magneto-optical film include terbium, iron,
A cobalt ternary alloy and a dysprosium-iron-cobalt ternary alloy have been proposed (Japanese Patent Publication No. 1-23927). However, these magneto-optical films have the disadvantage that they cannot record at low recording power and at the speed of light.

[0005] If the recording power of the laser is lowered or the recording speed is increased, it becomes difficult to heat the magneto-optical film to a high temperature, so a material with a low Curie point must be used. However, materials with a low Curie point have the disadvantage of having a small Kerr effect.

As a method for solving this problem, there is a method using a conventionally known exchange coupling.

Next, an example of a magneto-optical film using exchange coupling (
This will be explained using Japanese Patent Publication No. 2-35371).

A first magneto-optical film made of an iron-terbium amorphous alloy that can be perpendicularly magnetized, has a low Curie point and a high coercive force, and an iron-cobalt-gadolinium amorphous alloy that has a high Curie point and a low coercive force on the substrate. A second magneto-optical film made of an alloy and a transparent protective film made of silicon oxide are formed in this order. The first magneto-optical film has a Curie temperature of 120 to 130°C, a coercive force of 10 k Oe, and a film thickness of 500 angstroms, and the second magneto-optical film has a Curie temperature of 210 to 220°C and a coercive force of 0.5.
The film thickness is less than k oersted and 300 angstroms.

Magneto-optical recording media using exchange coupling can write on a high coercive force film with a low Curie point with a small recording power, and the written recording marks are transferred to the low coercive force film with a high Curie point. Therefore, by irradiating the transferred recording mark with a focused laser beam of low power and reading it out, it is possible to perform reading with a large Kerr effect.

0010

[Problems to be Solved by the Invention] However, the above-mentioned conventional magneto-optical recording medium and its recording and reproducing method have the disadvantage that it is not possible to increase the recording sensitivity and it is not possible to record and reproduce at high speed and optical density. .

[0011]

[Means for Solving the Problems] The magneto-optical recording medium of the present invention has a first magneto-optical film and a second magneto-optical film provided on a substrate in this order, and a second magneto-optical film is formed by a focused laser beam. A magneto-optical recording medium in which information is written by heating the film to near the Curie point, and information is read by moving and irradiating a first magneto-optical film with focused laser light. , the first magneto-optical film is made of iron, cobalt,
It is composed of an amorphous alloy of iron group transition metals and rare earth transition metals containing gadolinium, has a Curie point of 200°C or higher, and has a low coercive force of less than 0.5 k Oe at temperatures between 10°C and 90°C. The second magneto-optical film exhibits iron-transition metal dominant ferrimagnetism and has a film thickness of approximately 150 to 300 angstroms. It is composed of an amorphous alloy of 11
The film has a Curie point of 0° C. or higher, exhibits iron-group transition metal-dominant ferrimagnetism with a high coercive force of 1 k Oe or more at 90° C. or lower, and is perpendicularly magnetizable with a film thickness of about 350 angstroms or more; The first magneto-optical film and the second magneto-optical film are configured to be exchange-coupled at a temperature of 10° C. or more and 90° C. or less.

Further, the method for recording and reproducing a magneto-optical recording medium of the present invention includes providing a first magneto-optical film and a second magneto-optical film on a substrate in this order, and recording a second magneto-optical film using a focused laser beam. Information is written by heating the membrane to near the Curie point,
A magneto-optical recording medium in which information is read by moving and irradiating a first magneto-optical film with a focused laser beam, the first magneto-optical film containing iron, cobalt and gadolinium. It is composed of an amorphous alloy of iron group transition metals and rare earth transition metals, and has a Curie point of 200°C or higher and a temperature of 0.5k at 10°C or higher and 90°C or lower.
The second magneto-optical film exhibits iron group transition metal dominant ferrimagnetism with a coercive force less than Oersted, and has a film thickness of about 150 to 300 angstroms.
It is composed of an amorphous alloy of iron group transition metals containing terbium and titanium and rare earth transition metals, and has a Curie point of 110°C or higher at 200°C or lower and a temperature of 1 at 90°C or lower.
The film exhibits iron group transition metal dominant ferrimagnetism with a high coercive force of K oersted or more, and has a film thickness of about 350 angstroms or more and is perpendicularly magnetizable, and the first magneto-optical film and the second magneto-optical film By using a magneto-optical recording medium that is exchange-coupled at a temperature of 10° C. or higher and 90° C. or lower, a focused laser beam is passed through the substrate while rotating the medium to the first magneto-optical film and the second magneto-optical film. The first magneto-optical film is configured to record information by irradiating the first magneto-optical film with a focused laser beam having a power lower than that used for recording, and to reproduce information by irradiating the first magneto-optical film through the substrate with a focused laser beam having a power lower than that used for recording. Ru.

In addition, the magneto-optical recording medium of the present invention has a transparent interference film, a first magneto-optical film, a second magneto-optical film, a protective film, and a heat dissipation film provided in this order on a substrate, and the magneto-optical recording medium is provided with a transparent interference film, a first magneto-optical film, a second magneto-optical film, a protective film, and a heat dissipation film in this order. A magneto-optical film in which information is written by heating the second magneto-optical film to near the Curie point, and information is read by moving and irradiating the first magneto-optical film with a focused laser beam. In the recording medium, the first magneto-optical film is composed of an amorphous alloy of an iron group transition metal containing iron, cobalt, and gadolinium and a rare earth transition metal, and
It has a Curie point of 00°C or higher, exhibits iron-group transition metal-dominant ferrimagnetism with a low coercive force of less than 0.5 k Oe at temperatures of 10°C or higher and 90°C or lower, and has a film thickness of 150°C or higher.
The second magneto-optical film is made of an amorphous alloy of an iron group transition metal containing iron, terbium, and titanium and a rare earth transition metal;
Curie point of 110℃ or higher at 200℃ or lower and 9
It exhibits iron group transition metal dominant ferrimagnetism with a high coercive force of 1 k oersted or more at temperatures below 0°C, and the film thickness is 350°C.
It is a film that can be perpendicularly magnetized over approximately angstroms,
The first magneto-optical film and the second magneto-optical film are configured to be exchange-coupled at a temperature of 10° C. or more and 90° C. or less.

Further, the method for recording and reproducing a magneto-optical recording medium of the present invention includes providing a transparent interference film, a first magneto-optical film, a second magneto-optical film, a protective film, and a heat dissipating film on a substrate in this order. The second magneto-optical film is heated near the Curie point by the laser beam to write information, and the focused laser beam is then heated to the first magneto-optical film.
A magneto-optical recording medium in which information is read by irradiating a magneto-optical film while moving the film, the first magneto-optical film being made of an iron-transition metal containing iron, cobalt, and gadolinium, and a rare-earth transition metal. It is composed of an amorphous alloy with metal and has a Curie point of 200°C or higher and a temperature of 10°C.
The film exhibits iron group transition metal dominant ferrimagnetism with a low coercive force of less than 0.5 k oersteds at 90° C. or below, and has a film thickness of about 150 to 300 angstroms,
The second magneto-optical film is made of an amorphous alloy of an iron group transition metal containing iron, terbium, and titanium and a rare earth transition metal, and has a Curie point of 110°C or higher at 200°C or lower. The film exhibits iron group transition metal dominant ferrimagnetism with a high coercive force of 1 k oersted or more at 90° C. or less, and can be perpendicularly magnetized with a film thickness of about 350 angstroms or more, and the first magneto-optical film and the second The magneto-optical film is a magneto-optical recording medium exchange-coupled at a temperature of 10°C to 90°C, and while rotating the medium, a focused laser beam is passed through the substrate to the first magneto-optical film and the second magneto-optical film. Information is recorded by irradiating the first magneto-optical film with a focused laser beam having a power lower than that used for recording, and information is reproduced by irradiating the first magneto-optical film through the substrate with a focused laser beam having a power lower than that used for recording. It is configured as follows.

[0015]

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

FIG. 1 is a schematic cross-sectional view showing one embodiment of the present invention.

In the magneto-optical recording medium shown in FIG. 1, a transparent interference film 2 is provided on a substrate 1, and a transparent interference film 2 is formed on the transparent interference film 2. It is an amorphous alloy with a high Curie point of 200℃ or higher and has a temperature of 0.5 at 10℃ or higher and 90℃ or lower.
It has a low coercive force of less than K Oersteds, exhibits TM dominant ferrimagnetism at that temperature, and has a film thickness of 150 to 300.
A readout film 3 of about angstrom is provided, and iron and
TM-RE amorphous alloy containing terbium and titanium with a Curie point of 200°C or lower and 110°C or higher and 90°C.
High coercive force of 1k oersted or more below ℃ and 10℃
A writing film 4 is provided which exhibits TM dominant ferrimagnetism at temperatures below 90° C. and is perpendicularly magnetizable with a film thickness of approximately 350 angstroms or more, and at least a protective film 5 is provided thereon, and the reading film 3 and writing film 4 are provided. 4 is exchange-coupled at a temperature of 10°C or more and 90°C or less.

Laser light for recording and reproducing is incident through the substrate 1 and focused by focusing servo so that it has a diameter of about 1.4 μm in the vicinity of the readout film 3 . A semiconductor laser with a wavelength of about 8300 angstroms is used as a laser light source.

As the substrate 1, a glass plate coated with a photopolymer, an acrylic resin plate coated with a photopolymer, a polycarbonate resin plate, or the like is used, and tracking servo is performed by providing guide grooves. In particular, a glass plate coated with a photopolymer is preferable as the substrate 1. The materials of the transparent interference film 2 include silicon nitride, a mixture of zinc sulfide and metal oxide, a mixture of zinc sulfide and metal nitride, a mixture of zinc sulfide and metal carbide, a mixture of zinc sulfide and metal fluoride, Mixtures of zinc sulfide and metal borides, mixtures of zinc sulfide and other metal sulfides, and high refractive index multi-metal oxides are preferred.

The material of the protective film 5 may be silicon nitride, a mixture of zinc sulfide and metal oxide, a mixture of zinc sulfide and metal nitride, a mixture of zinc sulfide and metal carbide, or a mixture of zinc sulfide and metal fluoride. Mixtures, mixtures of zinc sulfide and metal borides, mixtures of zinc sulfide and other metal sulfides are preferred.

The readout film 3 is made of an amorphous alloy of iron, cobalt, and gadolinium, has a film thickness of about 150 to 300 angstroms, and has a Curie point of 200° C. or more.
It is essential that the writing film 4 has a low coercive force of less than 0.5 k oersteds at temperatures above 10°C and below 90°C and exhibits TM dominant ferrimagnetism at that temperature. It is an alloy film that can be perpendicularly magnetized when the film thickness is about 350 angstroms or more, has a Curie point of 110°C or more below 200°C, has a high coercive force of 1 k Oe or more at 10°C or above and below 90°C, and is TM dominant at that temperature. It is essential to exhibit ferrimagnetism of
It is essential that the read film 3 and the write film 4 perform TM dominant/TM dominant exchange coupling at a temperature of 10° C. or higher and 90° C. or lower.

The present inventors tried various materials and physical properties for the reading film 3 and the writing film 4, and as a result, they arrived at the present invention.

If the thickness of the readout film 3 becomes thinner than about 150 angstroms, the amplitude of the raw signal during reproduction becomes small, which becomes a problem.

Furthermore, if the thickness of the readout film 3 is greater than about 300 angstroms, recording marks of good shape cannot be formed, resulting in a poor signal-to-noise ratio (C/N), which poses a problem.

[0025] The temperature of the readout film during reproducing recorded marks is about 10°C or more and 90°C or less. At this temperature, unless the coercive force of the read film is as low as less than 0.5 k Oe, the magnetization pattern written on the write film will not be transferred well, resulting in a problem of poor C/N. The Curie temperature of the readout film needs to be 200° C. or higher to increase the Kerr effect. The thickness of the writing film needs to be about 350 angstroms or more in view of the stability of recording marks against external magnetic fields, and in order to obtain a good C/N, it is necessary to be a film that can be perpendicularly magnetized. From the viewpoint of the stability of recording marks against external magnetic fields, the coercive force of the writing film at temperatures between 10°C and 90°C must be 1k Oe or more, and in order to have high recording sensitivity, the Curie of the writing film must be The point is 200℃
It is necessary that the temperature is below 110°C. There are four types of exchange coupling states between the read film and the write film when reproducing recorded marks: TM dominant/TM dominant, TM dominant/RE dominant, RE dominant/TM dominant, and RE dominant/RE dominant. However, from the viewpoint of stability of recording marks against external magnetic fields, TM
Dominant/TM Dominant or RE Dominant/R
An E-dominant exchange coupling state is desirable. From the viewpoint of C/N, a TM dominant/TM dominant exchange coupling state is further desirable.

Next, regarding another embodiment of the present invention, FIG.
This will be explained with reference to the schematic cross-sectional view shown in FIG.

The magneto-optical recording medium shown in FIG. 2 has at least a transparent interference film 2, a reading film 3, a writing film 4, a protective film 5, and a heat dissipating film 6 provided in this order on a substrate 1. 4 is 10
Exchange coupling should occur at a temperature of ℃ or above and 90℃ or below. The material of the heat dissipation film 6 is preferably an aluminum alloy such as an aluminum-titanium alloy, an aluminum-chromium alloy, or an aluminum-tantalum alloy.

Since the magneto-optical recording medium shown in FIG. 2 can increase the power of the reproducing laser beam, it can eliminate the adverse effects of the noise of the reproducing circuit system and the noise of the semiconductor laser, and improve the C/N. be able to.

Next, using the magneto-optical recording medium shown in FIGS. 1 and 2, we will explain the magneto-optical recording medium of the present invention, which can achieve high recording density, high information transfer rate, and lower overall bit error rate. An embodiment of the recording and reproducing method will be described using block diagrams shown in FIGS. 3 to 6.

The recording and reproducing method for these magneto-optical recording media will be explained using as an example a recording and reproducing system in which the system including the recording system and the reproducing system can be regarded as a duobinary transmission line, which is a type of partial response digital transmission line. .

FIG. 3 is a block diagram showing a first embodiment of a recording/reproducing method for a magneto-optical recording medium.

The recording and reproducing method for a magneto-optical recording medium shown in FIG. a modulo-2 addition circuit 32, which is a recording-side equalization circuit for creating binary intermediate series data to suppress
A laser drive circuit 33 is also provided. That is, in the recording process, source data a is passed through a modulation encoder 31 and encoded recording data is converted into intermediate series data via a modulo 2 addition circuit 32 which is a recording side equalization circuit, and a semiconductor laser is used as a light source. Information is recorded in the form of a recording mark string on the magneto-optical recording medium shown in FIGS. 1 and 2 by a recording/reproducing head. The system including the semiconductor laser, the recording/reproducing head, and the magneto-optical recording medium described here is shown as a recording/reproducing analog system 34.

On the other hand, on the reproduction side, there is a read amplifier 35 and a ternary level discriminator 36 for identifying the binary intermediate series data from the ternary signal read out in opposition to the recording side equalization circuit.
and a modulo 2 addition circuit 38 which is a reproduction side equalization circuit,
It includes a demodulation encoder 39 for reproducing the source data sequence and a clock regeneration system 37.

The block diagram of FIG. 3 will be explained in more detail using the drawings of FIGS. 7 to 9.

FIG. 7(a) is an example of data conversion when there is no recording side equalization circuit, and FIG. 7(b) is an example of data conversion when there is a recording side equalization circuit.

As shown in FIG. 7(a), if the reproduced data is erroneously reproduced due to noise during recording and reproduction,
Data error propagation occurs after demodulation. On the other hand, Figure 7
As shown in (b), by converting the information sequence, which is recorded data, into intermediate sequence data in the recording side equalization circuit, bit reading errors due to noise in the recording/reproducing system are propagated (
error propagation) can be significantly improved. At this time, the recorded mark string recorded on the magneto-optical recording medium is a binary digital information string with vertical magnetization directed upward or downward, but during reading, interference between recorded marks (hereinafter referred to as intersymbol interference) occurs. This causes distortion of the read signal waveform and a decrease in resolution.

The recording and reproducing method for a magneto-optical recording medium of the present invention actively uses this intersymbol interference to construct a ternary recording and reproducing system.

FIG. 8 is a diagram for explaining the reading principle according to the present invention. Here, the record mark string recorded as binary information is converted into three values by intersymbol interference and read out. For information identification of the read signal, two levels of slice levels S1 and S2 are set as shown in FIG. 8(d). At this time, the identification at each slice level is "1" and "0", respectively.
” and “1”. At the same time, the clock regeneration system 37 detects peak values corresponding to "1", "0", and "1" of the read waveform, and determines the timing relationship between the bit information and the regenerated clock.

As shown in FIGS. 8(e), (f), and (g), the information sequence pulsed at each slice level is divided into the original binary data sequence by timing with the sampling clock as a data identification window. is converted to A source data sequence is reproduced from this demodulated data sequence through a demodulation encoder 39.

FIG. 9 shows the power spectrum in the partial response method in the recording and reproducing method of the magneto-optical recording medium shown in FIGS. 3 to 6.

As shown in the figure, this can be achieved with half the bandwidth compared to the method of reading recorded data as binary data. Therefore, twice as much information can be recorded and reproduced.

FIG. 4 is a diagram showing a second embodiment of the method for recording and reproducing a magneto-optical recording medium according to the present invention.

The recording and reproducing method for the magneto-optical recording medium shown in FIG. 4 differs from the embodiment shown in FIG. 3 in the following points.

An equalization filter 40 for the analog level read out is inserted on the reproduction side, and the configuration has the role of correcting waveform distortion in the recording/reproduction analog system to the duobinary type transmission line. This is a configuration that facilitates correction of waveform distortion due to recording power dependence in the recording/reproduction system and waveform distortion in the reproduction amplifier system, and realizes a partial response type equalization filter.

FIG. 5 shows a third embodiment of the method for recording and reproducing a magneto-optical recording medium according to the present invention.

The recording and reproducing method of the magneto-optical recording medium shown in FIG. 5 differs from the embodiment shown in FIG. 3 in the following points.

The reproduction side includes a ternary level determination system 56 for identifying binary intermediate series data from the ternary signal read out by the read amplifier 35, a modulo 2 addition circuit 58 consisting of a waveform equalizer, and a waveform equalizer. The equalizer controller 57 includes an equalizer control device 57 that adaptively controls the tap coefficients of the equalizer, and a demodulation encoder 59 that reproduces a source data sequence from a binary intermediate sequence.

At this time, the three-value level determination system 56 of the waveform equalizer includes a reproduced waveform equalization filter having variable taps and three levels.
It consists of a value level discriminator. Here, a reproduced clock is simultaneously generated by a three-level level discriminator that identifies binary intermediate series data from a three-level signal. At this time, the equalizer control device 57 controls the tap coefficients of the reproduced waveform equalization filter so that the square error of the average power between the intermediate data sequence demodulated by the mean square error method and the source information data sequence is minimized. This is a configuration that adaptively controls. In this adaptive control, in addition to the method of equalizing the sequentially read data, for example, for code correspondence, a method of providing a preamble period in the leading area of the sector part, a method of providing a preset area of several tracks, etc. This configuration optimizes the equalization characteristics.

FIG. 6 shows a fourth embodiment of the method for recording and reproducing a magneto-optical recording medium according to the present invention.

The method for recording and reproducing the magneto-optical recording medium shown in FIG. 6 differs from the embodiment shown in FIG. 5 in the following points.

This configuration has an equalizing filter 60 for the analog level read out on the playback side, and has the role of correcting waveform distortion in the recording/playback analog system to the duobinary transmission line. This is a configuration that facilitates correction of waveform distortion due to recording power dependence in the recording/reproduction system and waveform distortion in the reproduction amplifier system, and realizes a partial response type equalization filter.

In the embodiments shown in FIGS. 3 to 6, an example of a multilevel signal detection system in a magneto-optical recording medium using a partial response method is shown using a duobinary code.
Various other partial response codes may also be used. In this case, the recording side equalization circuit and the reproduction side equalization circuit can be handled by using an N-element modulo addition circuit. In addition, in the recording-side equalization circuit, a compensation circuit may be additionally inserted to equalize the recording timing etc. in advance, taking into consideration the characteristics of the shape of the recording mark in the recording/reproducing analog system.

[0053] By using the magneto-optical recording medium of the partial response type described above, the recording and reproducing method of the partial response type magneto-optical recording medium can more than double the recording density of information and The transfer rate can be improved, and the overall bit error rate can be lowered.

Next, regarding the magneto-optical recording medium of the present invention,
This will be explained using a specific example.

A glass disk substrate with a diameter of 200 mm and a thickness of 1.18 mm on which guide grooves are formed using photopolymer is annealed in vacuum at 100° C., then placed in a sputtering device and heated to a temperature of 5×10 −7 Torr or less. After evacuation, the photopolymer layer was reverse sputtered to a thickness of about 10 angstroms, and then a silicon target was sputtered using a mixed gas of argon and nitrogen to form a transparent interference film 22 of silicon nitride with a thickness of 750 angstroms.

Next, a readout film 23 of an amorphous alloy of iron, cobalt, and gadolinium having a thickness of approximately 200 angstroms was formed by sputtering an iron, cobalt, and gadolinium target using argon gas. The composition of iron, cobalt, and gadolinium in this readout film single layer is 6 atomic percent.
1.6 vs. 15.4 vs. 23.0, 10℃ or more 90℃
It exhibits TM dominant ferrimagnetism at the following temperatures, has a low coercive force of less than 0.5 k Oe, and has a Curie point of 200° C. or higher in that temperature range.

Immediately after forming the reading film, a writing film 24 of an amorphous alloy of iron, terbium, and titanium having a thickness of about 600 angstroms was formed by sputtering an iron-terbium-titanium target using argon gas. The composition of iron, terbium, and titanium in this single layer writing film is 77.7:20.5:1.8 in atomic percent, and exhibits TM dominant ferrimagnetism at temperatures above 10°C and below 90°C. In terms of temperature, it has a high coercive force of 1 k Oe or more and exhibits a Curie point of approximately 135°C.

A protective film 25 of silicon nitride having a thickness of 1500 angstroms was formed on the writing film 24 by sputtering a silicon target using a mixed gas of argon and nitrogen.

A heat dissipating film 26 of aluminum/titanium alloy with a thickness of 1000 angstroms is provided thereon by sputtering an aluminum/titanium alloy target (titanium content is approximately 1.0% by weight) with argon gas. It was taken out to the atmosphere.

Thereafter, a UV curable resin is spin-coated on the heat dissipation film 26, and UV irradiation is applied to form a bonded protective film of about 10 μm thick on the UV curable resin. They were bonded together by hot melt so that No. 21 was on the outside and each of the above films was on the inside.

The magneto-optical recording medium thus produced was rotated at 3600 rpm, and a semiconductor laser beam with a wavelength of 8300 angstroms was applied to the readout film 23 through the substrate 21.
The reproduction beam power used for the focusing servo and tracking servo, which was irradiated with a focus of approximately φ1.4 μm, was 3.3 mW. At a radius of 87.5 mm, a signal with a recording frequency of 10 MHz is output with a duty of 50.
% optical modulation, a recording power of 9 mW, and a recording magnetic field of 250 oersteds, a C/N of 59 dB was obtained, confirming that it is a magneto-optical recording medium with high recording sensitivity and high C/N.

Even when an external magnetic field of 700 Oe was applied to this optical disk, there was no change in the recorded signal, and it was confirmed that the signal stability was good.

Next, using the recording/reproducing system shown in FIG. 6 on this optical disc, the minimum bit length is 0.4 using the duobinary code.
When ultra-high density recording of 6 μm was performed over the entire disk area and the bit error rate was measured, it was confirmed that there were very few errors.

Next, when this optical disk was stored in a high temperature and high humidity environment of 80°C and 80% for 500 hours, the above bit error rate was measured, and the errors were very small. It was confirmed that this is a recording/playback method.

[0065]

[Effects of the Invention] The magneto-optical recording medium and the recording and reproducing method thereof of the present invention have high recording sensitivity and can perform high-speed recording and reproducing.
This also has the effect of enabling high-density recording and reproduction.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing one embodiment of the present invention;

[Figure 2]
A schematic sectional view showing another embodiment of the present invention,

[Figure 3] Figure 1,
The first recording/reproducing method using the magneto-optical recording medium shown in FIG.
A block diagram showing an example of

FIG. 4 is a block diagram showing a second example of the recording and reproducing method using the magneto-optical recording medium shown in FIGS. 1 and 2;

FIG. 5 is a block diagram showing a third example of the recording and reproducing method using the magneto-optical recording medium shown in FIGS. 1 and 2;

[Figure 6
] A block diagram showing a fourth example of the recording and reproducing method using the magneto-optical recording medium shown in FIGS. 1 and 2,

FIG. 7 is a conversion explanatory diagram for explaining an example of data conversion in the recording/reproducing method shown in FIGS. 3 to 6;

FIG. 8 is a reading principle explanatory diagram for explaining the reading principle in the method for reproducing the magneto-optical recording medium shown in FIGS. 3 to 6;

FIG. 9 is a power spectrum diagram in the partial response method in the recording and reproducing method of the magneto-optical recording medium shown in FIGS. 3 to 6;

[Explanation of symbols]

1　　　　Substrate 2 Transparent interference film 3 Readout membrane 4 Writing membrane 5 Protective film 6 Heat dissipation film 31 Modulation encoder 32 Modulo 2 addition circuit 33 Laser drive circuit 34 Recording/playback analog system 35 Read amplifier 36 3-value level discriminator 37 Clock regeneration system 38 Modulo 2 addition circuit 39 Demodulation encoder 40, 60 Equalization filter 56 3-value level judgment system 57 Equalizer control device 58 Modulo 2 addition circuit 59 Demodulation encoder a Source data b Demodulated data

Claims (12)

[Claims] 1. A first magneto-optical film and a second magneto-optical film are provided in this order on a substrate, and the second magneto-optical film is heated to near the Curie point by a focused laser beam to write information. A magneto-optical recording medium in which information is read by moving and irradiating a focused laser beam onto a first magneto-optical film, the first magneto-optical film being made of iron, cobalt, It is composed of an amorphous alloy of an iron group transition metal containing gadolinium and a rare earth transition metal, and has 200%
It has a Curie point of 10°C or higher, exhibits iron group transition metal dominant ferrimagnetism with a low coercive force of less than 0.5k Oersteds at 10°C or higher and 90°C or lower, and has a film thickness of 150 to 30°C.
The second magneto-optical film is made of an amorphous alloy of an iron group transition metal containing iron, terbium, and titanium and a rare earth transition metal, and has a thickness of about 20 angstroms.
Curie point of 110℃ or higher at 0℃ or lower and 90℃
The following is a film that exhibits iron group transition metal dominant ferrimagnetism with a high coercive force of 1 k Oe or more, and has a film thickness of about 350 angstroms or more and can be perpendicularly magnetized, and the first magneto-optical film and the second optical What is a magnetic film?9
A magneto-optical recording medium characterized by exchange coupling at temperatures below 0°C. 2. A first magneto-optical film and a second magneto-optical film are provided in this order on a substrate, and the second magneto-optical film is heated to near the Curie point by a focused laser beam to write information. A magneto-optical recording medium in which information is read by moving and irradiating a focused laser beam onto a first magneto-optical film, the first magneto-optical film being made of iron, cobalt, It is composed of an amorphous alloy of an iron group transition metal containing gadolinium and a rare earth transition metal, and has 200%
It has a Curie point of 10°C or higher, exhibits iron group transition metal dominant ferrimagnetism with a low coercive force of less than 0.5k Oersteds at 10°C or higher and 90°C or lower, and has a film thickness of 150 to 30°C.
The second magneto-optical film is made of an amorphous alloy of an iron group transition metal containing iron, terbium, and titanium and a rare earth transition metal, and has a thickness of about 20 angstroms.
Curie point of 110℃ or higher at 0℃ or lower and 90℃
The following is a film that exhibits iron group transition metal dominant ferrimagnetism with a high coercive force of 1 k Oe or more, and has a film thickness of about 350 angstroms or more and can be perpendicularly magnetized, and the first magneto-optical film and the second optical What is a magnetic film?9
Using a magneto-optical recording medium that is exchange-coupled at 0° C. or lower, irradiating the first magneto-optical film and the second magneto-optical film with a focused laser beam through the substrate while rotating the medium. A magneto-optical recording medium, characterized in that information is recorded by a magneto-optical recording medium, and information is reproduced by irradiating the first magneto-optical film through the substrate with a focused laser beam having a power lower than that used during the recording. How to record and play. 3. The recording side includes a modulation encoder that modulates source data into binary data, a recording side equalization circuit that generates binary intermediate series data to suppress error propagation in the recording/reproducing system, and a semiconductor. a laser drive circuit, and on the reproduction side, a readout amplifier, and a reproduction side equalization circuit that opposes the recording side equalization circuit and identifies the binary intermediate series data from the read multivalued signal; 3. The method for recording and reproducing a magneto-optical recording medium according to claim 2, further comprising a demodulation encoder for reproducing demodulated data from the identified intermediate sequence data, and recording and reproducing a multi-level signal. 4. The recording side includes a modulation encoder that modulates source data into binary data, a recording side equalization circuit that generates binary intermediate series data to suppress error propagation in the recording/reproducing system, and a semiconductor device. a laser drive circuit, and on the reproduction side, a readout amplifier, a waveform equalizer that opposes the recording side equalization circuit and identifies the binary intermediate series data from the read multilevel signal; 3. The apparatus according to claim 2, further comprising an equalizer control device that adaptively controls tap coefficients of a waveform equalizer and a demodulation encoder that reproduces demodulated data, and performs recording and reproduction of multilevel signals. A method for recording and reproducing a magneto-optical recording medium. 5. A transparent interference film, a first magneto-optical film, a second magneto-optical film, a protective film, and a heat dissipation film are provided on the substrate in this order, and the second magneto-optical film is heated to the Curie point using a focused laser beam. A magneto-optical recording medium in which information is written by heating the vicinity of the first magneto-optical film, and information is read by moving and irradiating the first magneto-optical film with a focused laser beam, the first magneto-optical recording medium The magneto-optical film is composed of an amorphous alloy of iron group transition metals containing iron, cobalt, and gadolinium and rare earth transition metals, and has a Curie point of 200°C or higher and a temperature of 10°C to 90°C. The second magneto-optical film contains iron, terbium, and titanium, exhibiting iron-group transition metal-dominant ferrimagnetism with a low coercive force of less than 0.5 k Oe, and having a film thickness of approximately 150 to 300 angstroms. It is composed of an amorphous alloy of an iron group transition metal and a rare earth transition metal, and has a Curie point of 110°C or higher at 200°C or lower, and has a high coercive force of 1 k Oe or higher at 90°C or lower. The film exhibits dominant ferrimagnetism and is perpendicularly magnetizable with a film thickness of about 350 angstroms or more, and the first magneto-optical film and the second magneto-optical film are
A magneto-optical recording medium characterized in that the magneto-optical film is exchange-coupled at a temperature of 10°C or more and 90°C or less. 6. The magneto-optical recording medium according to claim 5, wherein the transparent interference film is a silicon nitride film. 7. The magneto-optical recording medium according to claim 5, wherein the protective film is a silicon nitride film. 8. The magneto-optical recording medium according to claim 5, wherein the heat dissipation film is made of an aluminum alloy. 9. The magneto-optical recording medium according to claim 5, wherein the substrate is glass. 10. A transparent interference film, a first magneto-optical film, a second magneto-optical film, a protective film, and a heat dissipation film are provided on the substrate in this order,
The second magneto-optical film is heated near the Curie point by a focused laser beam to write information, and the information is read by moving and irradiating the first magneto-optical film with the focused laser beam. In the magneto-optical recording medium, the first magneto-optical film is composed of an amorphous alloy of an iron group transition metal containing iron, cobalt, and gadolinium and a rare earth transition metal, and The film has a Curie point of , exhibits iron group transition metal dominant ferrimagnetism with a low coercive force of less than 0.5 k oersteds at 10° C. or higher and 90° C. or lower, and has a film thickness of about 150 to 300 angstroms, and has a film thickness of about 150 to 300 angstroms. The second magneto-optical film is composed of an amorphous alloy of an iron group transition metal containing iron, terbium, and titanium and a rare earth transition metal, and has a Curie point of 110°C or higher at 200°C or lower and 90°C. The film exhibits iron-group transition metal-dominant ferrimagnetism with a high coercive force of 1 k Oe or more at temperatures below 10°C, and is perpendicularly magnetizable with a film thickness of about 350 angstroms or more, and the first magneto-optical film and the second A magneto-optical film is a magneto-optical recording medium exchange-coupled at a temperature of 10°C to 90°C, and while the medium is rotated, a focused laser beam is passed through the substrate to the first magneto-optical film and the second magneto-optical film. Recording of information by irradiating the first magneto-optical film, and reproducing information by irradiating the first magneto-optical film through the substrate with a focused laser beam having a power lower than that used for recording. A method for recording and reproducing a magneto-optical recording medium, characterized by: 11. The recording side includes a modulation encoder that modulates source data into binary data, a recording side equalization circuit that generates binary intermediate series data to suppress error propagation in the recording/reproducing system, and a semiconductor device. a laser drive circuit, and on the reproduction side, a readout amplifier, and a reproduction side equalization circuit that opposes the recording side equalization circuit and identifies the binary intermediate series data from the read multivalued signal; 11. The method for recording and reproducing a magneto-optical recording medium according to claim 10, further comprising a demodulating encoder for reproducing the source data from the identified intermediate series data, and recording and reproducing a multilevel signal. 12. The recording side includes a modulation encoder that modulates source data into binary data, a recording side equalization circuit that generates binary intermediate series data to suppress error propagation in the recording/reproducing system, and a semiconductor device. a laser drive circuit, and on the reproduction side, a readout amplifier, a waveform equalizer that opposes the recording side equalization circuit and identifies the binary intermediate series data from the read multilevel signal; Claim 10, characterized in that it comprises an equalizer control device that adaptively controls tap coefficients of a waveform equalizer, and a demodulation encoder that reproduces the source data, and performs recording and reproduction of multilevel signals. A method for recording and reproducing the magneto-optical recording medium described above.