JPH08315436A - Magneto-optical recording medium and information recording and reproducing method using that medium - Google Patents

Abstract

PURPOSE: To obtain a high-density magneto-optical recording medium at a low material cost which realizes magnetic superhigh resolution in a magneto- optical recording medium having all magnetic layers of thin films and enables fast recording, and to obtain an information reproducing and recording method. CONSTITUTION: In this magneto-optical recording medium, the total magnetization direction is antiparallel when a reproducing layer and a recording layer are in an exchange bonding state. The intermediate layer consists of a magnetic phase transition material having higher transition temp. of reversible transition from antiferromagnetism to ferromagnetism than room temp. At room temp., the reproducing layer and the recording layer are magnetostatically coupled and the sublattice magnetic moment of the same kind of element is oriented in the opposite direction. At a temp. where the intermediate layer shows transition to ferromagnetism, the sublattice magnetic moment of the same kinds of elements in the reproducing layer and the recording layer is oriented parallel to each other by the exchange bonding. Thus, recording and reproducing are performed in this medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium for recording / reproducing information with a laser beam by utilizing a magneto-optical effect, and a magneto-optical reproducing method and a magneto-optical recording capable of increasing the density of the medium. It concerns media.

[0002]

2. Description of the Related Art As a rewritable high density recording system,
Using the thermal energy of a semiconductor laser to write magnetic domains in a magnetic thin film to record information, using the magneto-optical effect,
Attention has been paid to a magneto-optical recording medium for reading this information.
Further, in recent years, there is an increasing demand for increasing the recording density of this magneto-optical recording medium to make it a recording medium having a larger capacity.

The linear recording density of an optical disk such as the magneto-optical recording medium largely depends on the laser wavelength of the reproducing optical system and the numerical aperture of the objective lens. That is, since the diameter of the beam waist is determined when the laser wavelength λ of the reproduction optical system and the numerical aperture NA of the objective lens are determined, the mark period that can be reproduced and detected is limited to about λ / 2NA.

On the other hand, track density is limited mainly by crosstalk. This crosstalk is mainly determined by the distribution (profile) of the laser beam on the medium surface, and is represented by a function of λ / 2NA, like the mark period.

Therefore, in order to realize high density in the conventional optical disk, it is necessary to shorten the laser wavelength of the reproducing optical system and increase the numerical aperture NA of the objective lens.
However, it is not easy to shorten the laser wavelength due to problems such as reduced efficiency of the element and heat generation, and when the numerical aperture of the objective lens is increased, the distance between the lens and the disk becomes too close and mechanical such as collision occurs. The problem occurs. Therefore, a technique for improving the recording density by devising the configuration of the recording medium and the reading method has been developed.

For example, Japanese Patent Laid-Open No. 3-93056 attempts to improve the recording density by using a medium composed of a reproducing layer, an intermediate layer and a recording layer. This is because a medium having a reproducing layer, an intermediate layer and a recording layer is irradiated with a light spot while advancing at a certain linear velocity, and in the temperature distribution of the medium generated at that time, the magnetization of the reproducing layer in the high temperature region is The magnetic field information of the recording layer is transferred and reproduced only in the reproducing layer in the low temperature region by making it uniform in the direction of the magnetic field, reducing the intersymbol interference during reproduction, and reproducing the signal with a period less than the light diffraction limit. If possible, we are trying to improve the recording density.

Further, for example, in Japanese Patent Laid-Open No. 3-93058, an attempt is made to improve the recording density by basically using a medium composed of a reproducing layer and a recording layer. As shown in FIG. 3, a medium having a reproducing layer 1, an auxiliary layer 2, an intermediate layer 3 and a recording layer 4 is moved at a certain linear velocity (direction 9 of movement) (FIG. 3 (b)). Prior to the information reproduction, the medium is irradiated with a light spot after masking the magnetic domain information of the recording layer 4 by aligning the magnetization direction of the reproducing layer 1 in the − direction with the initialization magnetic field 12, and By reducing the effective size of the reproducing spot by transferring the magnetic domain information of the recording layer 4 to the reproducing layer 1 with the assistance of the reproducing magnetic field 11 in the high temperature region of the temperature distribution (FIG. 3C). The recording marks below the diffraction limit of light can be reproduced to improve the linear density and the recording density.

[0008]

However, the above-mentioned JP-A-3-93056 and JP-A-3-93058.
In the magneto-optical recording medium described in Japanese Patent Laid-Open Publication No.
In order to obtain N), it is necessary to increase the thickness of the reproducing layer so that the magnetic domain information of the recording layer can be sufficiently masked. Specifically, as described in JP-A-4-255938, when the film thickness of the reproducing layer is 15 nm or less, the influence of the layer below the reproducing layer is 25% or more, and thus super-resolution reproduction becomes impossible. , 20nm to get the required signal, practically 3
A reproducing layer having a film thickness of 0 nm or more is required. As described above, in the magneto-optical recording medium, since it is necessary to mask the magnetic domain information of the recording layer, it is not possible to reduce the film thickness of the reproducing layer and thus the total magnetic layer.

In recent years, there has been an increasing demand for increasing the recording speed by increasing the linear velocity of a magneto-optical recording medium. However, a medium having a large magnetic layer thickness has a high heat capacity as a whole, and thus requires a large optical power for recording. Since the output of optical power of a semiconductor laser or the like is limited, it is difficult for the magneto-optical recording medium to meet this demand. Further, it is impossible to increase the C / N as an enhanced structure by providing a reflective layer.

Further, rare earth metals, which are generally high in material cost, are often used as the magnetic material, and when a thick magnetic layer is used, the material cost of the medium becomes high, and it is difficult to provide an inexpensive magneto-optical recording medium.

Therefore, in the above-described magneto-optical recording medium and method, it is difficult to realize high density recording by magnetic super-resolution at the same time as high-speed recording and provide an inexpensive magneto-optical recording medium.

Further, in the above-described magneto-optical recording medium and method, it is necessary to apply an external magnetic field during reproduction, and it is difficult to provide a high-density magnetic super-resolution with an inexpensive magneto-optical recording device. Is.

In view of the above problems, the present invention realizes magnetic super-resolution in a magneto-optical recording medium in which all magnetic layers are thinned, and high-speed recording is possible with a high-density magneto-optical recording medium of low material cost and the medium. An object of the present invention is to provide a good information recording / reproducing method using.

[0014]

The above-mentioned object is to provide a first magnetic layer, a second magnetic layer, and a third magnetic layer each of which is at least a perpendicular magnetization film.
The magnetic layer is laminated on the substrate in the order of the first magnetic layer, the third magnetic layer, and the second magnetic layer from the light incident surface, and when the first magnetic layer and the second magnetic layer are exchange-coupled, Magnetization directions are antiparallel, and the three magnetic layers are made of a magnetic phase transition material having a temperature (called magnetic transition temperature) higher than room temperature at which reversible transition from antiferromagnetism to ferromagnetism occurs. Above the temperature at which the first magnetic layer and the second magnetic layer are magnetostatically coupled, the sublattice magnetic moments of these same kind elements are oriented in opposite directions, and the third magnetic layer transitions to ferromagnetism. In the present invention, the magneto-optical recording medium is characterized in that the sublattice magnetic moments of the same element in the first magnetic layer and the second magnetic layer are oriented parallel to each other by exchange coupling.

Further, the present invention irradiates a light spot on the above-mentioned magneto-optical recording medium having information recorded on the second magnetic layer,
In a region where the third magnetic layer has a temperature lower than the magnetic transition temperature in the region within the light spot, the third magnetic layer has an antiferromagnetic phase, and the first magnetic layer and the second magnetic layer are magnetostatically coupled to each other. The directions of the sublattice magnetizations of the first magnetic layer and the second magnetic layer are opposite to each other, and the third magnetic layer is ferromagnetic in the region where the temperature of the third magnetic layer is equal to or higher than the magnetic transition temperature in the region of the light spot. Information of a magneto-optical recording medium in which the first magnetic layer and the second magnetic layer are exchange-coupled with each other, the magnetization information of the second magnetic layer is converted into an optical signal by a magneto-optical effect, and the signal is read as a recording signal. A recording / reproducing method is provided.

In the magneto-optical recording medium of the present invention, at least the first magnetic layer, the second magnetic layer, and the third magnetic layer, each of which is a perpendicular magnetization film, have the first magnetic layer, the third magnetic layer, and
The second magnetic layer is laminated on the substrate in this order, and the first magnetic layer and the second magnetic layer are formed.
In the exchange-coupled state, the magnetization direction of the magnetic layer is antiparallel, and the third magnetic layer is made of a magnetic phase transition material that reversibly transitions from antiferromagnetism to ferromagnetism. Above the temperature at which the layer and the second magnetic layer are magnetostatically coupled to each other, the sublattice magnetic moments of these similar elements are oriented in opposite directions, and the third magnetic layer transitions to ferromagnetism. The sublattice magnetic moments of the same element in the first magnetic layer and the second magnetic layer are oriented parallel to each other.

Therefore, the first magnetic layer and the second magnetic layer are magnetostatically coupled to each other in the low temperature region where the third magnetic layer is in the antiferromagnetic phase, and thus the first magnetic layer and the second magnetic layer. The sublattice magnetic moments of the layers are in opposite directions. Also,
In the high temperature region where the third magnetic layer is in the ferromagnetic phase, the first magnetic layer and the second magnetic layer are exchange-coupled via the third magnetic layer,
The sublattice magnetic moments of the first magnetic layer and the second magnetic layer are parallel to each other. At low temperatures, the sublattice magnetic moments of the first magnetic layer and the second magnetic layer are opposite to each other, and the Kerr rotation angle (θk) of these layers is apparently zero. Therefore, when reproducing with the magneto-optical recording medium of the present invention, the magnetization information recorded in the second magnetic layer is detected only in a part of the high temperature region in the light spot, and in the low temperature region in the light spot. Even when the laser beam passes through the first magnetic layer, the magnetic domain information of the second magnetic layer is not detected. Therefore, it is not necessary to mask the magnetic domain information of the recording layer in the super-resolution method described in the above-mentioned Japanese Patent Laid-Open No. 3-93058, and the thickness of the reproducing layer and thus the entire magnetic layer can be reduced. Therefore, in the magneto-optical recording medium and the reproducing method of the present invention, high linear velocity recording can be realized, the recording speed can be improved, the cost can be reduced, and at the same time, a film structure having a reflective film structure can be obtained, so that C / N can be increased.

The applicant of the present invention has also filed Japanese Patent Application Laid-Open No. 6-31444.
3 proposes a magneto-optical recording medium composed of at least a reproducing layer, a first magnetic layer and a second magnetic layer. Even when compared with the medium, the reproducing layer and the first magnetic layer are included in the medium of the present invention. Since the number of layers is one, the number of layers can be further reduced. Further, according to the magneto-optical recording medium and the reproducing method of the present invention, since it is not necessary to apply an external magnetic field during reproduction, it is possible to provide high density by magnetic super-resolution in an inexpensive magneto-optical recording device.

[0019]

The magneto-optical recording medium of the present invention and the recording / reproducing method using the medium will be described in detail below with reference to the drawings.

Hereinafter, the first magnetic layer is referred to as a reproducing layer, the second magnetic layer is referred to as a recording layer, and the third magnetic layer is referred to as an intermediate layer.

As shown in FIG. 1A, the magneto-optical recording medium of the present invention comprises at least a reproducing layer, an intermediate layer and a recording layer which are laminated. Further, a reflective layer may be further provided in order to further improve the characteristics. Further, an interference layer made of a dielectric material may be provided between the recording layer and the reflective layer. When this interference layer is provided, heat does not easily escape from the recording layer to the reflective layer, so that the enhanced structure allows recording with low power,
There are merits such as improved C / N.

As the reproducing layer, for example, a rare earth-iron group amorphous alloy, for example, GdFeCo, TbFeCo, GdTb.
FeCo, GdDyFeCo, NdGdFeCo, Gd
Co or the like is preferable.

The intermediate layer is located between the reproducing layer and the recording layer, and is antiferromagnetic at room temperature, and when the temperature rises, it changes from antiferromagnetic to ferromagnetic near the temperature at which the reproducing layer transitions to the perpendicular magnetization film. It consists of a material that reversibly undergoes a magnetic phase transition such that it returns to an antiferromagnetic material at room temperature. The temperature at which the antiferromagnetism transitions to the ferromagnetism and the temperature at which the ferromagnetism transitions to the antiferromagnetism do not have to match. Then, in the low temperature region in the light spot, the intermediate layer is antiferromagnetic and blocks the exchange force from the recording layer to the reproducing layer, and in the high temperature region, the intermediate layer becomes ferromagnetic and functions to mediate the exchange coupling force. Mainly has.

The material of the intermediate layer is, for example, FeRh.
Or MnSb or MnCrSb or HfT
A magnetic film mainly containing aFe or MnPt is preferable.
Among them, FeRh is most preferable because it can easily obtain a magnetic film having a magnetic phase transition temperature of room temperature or higher. In addition, P is added to FeRh for the purpose of adjusting the magnetic phase transition temperature.
You may add additional elements, such as d, Pt, and Ir. If the thickness of the intermediate layer is too small, it is insufficient to block the exchange force from the recording layer at room temperature, and if it is too large, the laser power during recording becomes large. Therefore, the thickness of the intermediate layer is preferably 1 nm to 15 nm, more preferably 4 nm to 10 nm or less. The temperature at which the intermediate layer transitions from antiferromagnetism to ferromagnetism needs to be at least between the maximum temperature in the light spot during reproduction and room temperature, and specifically, 80 ° C to 250 ° C. And preferably in the range of 120 ° C to 200 ° C.

In the high temperature region, the reproducing layer, the intermediate layer and the recording layer need to be thin enough to allow light to pass therethrough and cancel θk, and at least 30 nm or less, preferably 20 nm or less, more preferably 15 n.
m.

Next, the recording layer is preferably one having a large perpendicular magnetic anisotropy and capable of maintaining a stable magnetization state.
Most preferred are rare earth-iron group amorphous alloys such as FeCo, DyFeCo, TbDyFeCo. Alternatively, a garnet; a platinum group-iron group periodic structure film such as Pt / Co or Pd / Co; a platinum group-iron group alloy such as PtCo or PdCo may be used.

In order for the rotation of the plane of polarization to be canceled in the reproduction layer and the recording layer, the reproduction layer near the incident side has a large effect on the rotation of the plane of polarization, so that the reproduction layer and the recording layer have the same degree. When it has a complex refractive index, it may be thinner than the recording layer.

In the reproducing layer, the intermediate layer and the recording layer, Cr,
Elements such as Al, Ti, Pt, and Nb may be added to improve corrosion resistance.

The recording / reproducing process of the present invention will be described below.

First, a recording magnetic domain is formed in the recording layer of the magneto-optical recording medium of the present invention according to a data signal. Recording is performed by once erasing and then modulating the laser power while applying a magnetic field in the recording direction. Alternatively, the laser power is modulated while applying an external magnetic field to overwrite the old data with the new data. For these optical modulation recordings,
If the intensity of the laser beam is determined in consideration of the linear velocity of the recording medium so that only a predetermined area in the light spot is near the Curie temperature of the recording layer, a recording magnetic domain smaller than the diameter of the light spot can be formed. , A signal with a period less than the diffraction limit of light can be recorded. Alternatively, overwrite recording is performed by modulating the external magnetic field while irradiating a laser beam having a power such that the recording layer has a Curie temperature or higher. In this case, if the modulation speed is increased according to the linear velocity, a recording magnetic domain having a diameter smaller than that of the light spot can be formed, and as a result, a signal having a period less than the diffraction limit of light can be recorded.

Next, the reproducing method of the magneto-optical recording medium of the present invention will be described.

The intermediate layer of this medium is made of a magnetic phase transition material, and is antiferromagnetic at low temperatures including room temperature, and becomes ferromagnetic at high temperatures. The transition temperature is set so as to be within the temperature range within the light spot during reproduction. Therefore, from room temperature to the magnetic phase transition temperature, since the intermediate layer is always an antiferromagnetic material, the same number of opposite spins exist, and the exchange coupling force from the recording layer is effectively blocked by the intermediate layer. It For this reason, the reproducing layer and the recording layer are magnetostatically coupled in a low temperature region within the light spot during reproduction, and exchange coupling is performed through the intermediate layer in the high temperature region when they are ferromagnetic. The intermediate layer has the same number of sublattice magnetizations in opposite directions until the transition temperature is reached, and the overall magnetization is 0. Therefore, this state is indicated by a blank (hatched portion) in FIG. 2B. ing.

The reproducing layer and the recording layer are different in the type of sub-lattice magnetization that is dominant in ferrimagnetism (generally referred to as an antiparallel structure). More specifically, for example, when a rare earth (RE) -iron group (TM) element alloy is used for the reproducing layer and the recording layer, the reproducing layer has a rare earth element sublattice magnetization dominant (R).
The magnetic layer is E-rich), and the recording layer has the iron group element sublattice magnetization predominant (TM-rich) at room temperature, or vice versa. Of these, rare earth (R
When the E) -iron group (TM) element alloy is used, the reproducing layer is a rare earth element sublattice magnetization dominant (RE rich) magnetic layer, and the recording layer is an iron group element sublattice magnetization dominant (TM rich) at room temperature. The structure is more preferable because the magnetization information can be recorded in the recording layer in a low magnetic field. The anti-parallel structure needs to be achieved at least within the temperature range within the light spot during reproduction.

Therefore, when the magneto-optical recording medium of the present invention is reproduced, in the low temperature region within the light spot, the reproducing layer and the recording layer are magnetostatically coupled and the overall magnetization becomes parallel, so that the directions of the sub-lattice magnetizations are mutually opposite. In the opposite direction, the reproducing layer and the recording layer are exchange-coupled in the high temperature region, and the directions of the sublattice magnetization are parallel.

This state is shown in FIG. 2 (b). Figure 2
In (b), the white arrow indicates the overall magnetization, and the black arrow indicates the direction of the sublattice magnetization. For example, when a rare earth element-dominant iron-transition metal-dominant ferrimagnetic rare-earth-iron transition metal alloy is used in the reproducing layer and the recording layer, a white arrow indicates the entire magnetization. Indicates the sublattice magnetization of the iron group transition metal.

In the low temperature region, since the TM sublattice magnetic moments of the reproducing layer and the recording layer are oriented in mutually opposite directions, the light transmitted through the substrate first has its plane of polarization rotated in the reproducing layer and then Then, the recording layer is rotated in the opposite direction and returned to the magneto-optical recording device. Therefore, the rotation angle of the polarization plane polarized in the reproduction layer is made equal to the rotation angle of the polarization plane polarized in the recording layer. Then, the Kerr rotation angle is not affected by these layers. That is, even if the incident light passes through the reproducing layer, the magnetization information of the magnetic layer is not detected. Therefore, no signal is detected below the mask temperature Tm.

Therefore, as shown in FIG. 2A, an aperture portion where the recording mark is detected and a mask portion where the recording mark is not detected are generated in the light spot. That is, the diameter of the light spot is effectively reduced, and it is possible to detect a recording mark that is sufficiently smaller than the light spot that could not be detected conventionally.

Further, in the medium of the present invention, since the narrow high temperature region becomes the aperture region, it is possible to mask the information of the adjacent tracks in an isolated manner. Higher density can be achieved.

In the magneto-optical recording medium of the present invention, it is not necessary to mask the magnetization information of the recording layer with the reproducing layer and the layer having the same TM sublattice magnetic moment as that of the reproducing layer, so that the reproduced signal does not deteriorate in these layers. Can be as thin as. Therefore, the film thickness of the magnetic layer can be significantly reduced as compared with the conventional one.

The magnetostatic coupling is roughly proportional to the saturation magnetization of the recording layer and inversely proportional to the film thickness of the intermediate layer. Therefore, in order to reliably reverse the magnetization of the reproducing layer in the low temperature region, the saturation magnetization of the recording layer is increased in the low temperature region in the light spot, and the film reaches the limit at which the effect of the intermediate layer can be exhibited. It is better to reduce the thickness. If the radius of the recording magnetic domain (recording mark) is large with respect to the film thickness of the recording layer, the static magnetic field becomes weak and acts only around the recording magnetic domain. Therefore, the radius of the recording mark is made smaller than the film thickness. Is effective.

When the incident light is transmitted through the recording layer, the incident light is reflected on the recording layer in order to reflect the light to prevent the reduction of the returning light amount and enhance the incident light between the magnetic layer and the reflective layer. A reflective layer may be provided on the side opposite to the surface. In addition to the reflective layer, in order to enhance the interference effect, SiN, AlN
A dielectric such as _x , AlO _x , TaO _x , and SiO _x may be provided as the interference layer. This interference layer needs to have a film thickness that can cancel θk in the recording layer and obtain a desired reflectance. Alternatively, a heat conductive layer may be provided in order to improve the heat conductivity for the purpose of improving the shape of the magnetic domain when performing the magnetic field modulation overwrite. These reflection layer and heat conduction layer are made of Al, AlTa, AlTi, AlC.
r, Cu or the like may be used. Further, the reflective layer needs to be thin enough to reflect light, and the reflective layer and the heat conductive layer need to be thin so that the optical power is not too large. It is also possible to perform heat conduction and reflection in one layer. Furthermore, a protective coat made of the dielectric layer or polymer resin may be applied as a protective film.

[0042]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 In order to adjust the magnetic characteristics of FeRh, FeRh was deposited on a glass substrate using a DC magnetron sputtering device. The composition of FeRh is Fe
The power of each target of Rh and Rh was controlled so that the atomic ratio was Fe: Rh = 47: 53. The film thickness is 1000
Å Also, after depositing FeRh, SiN is used as a protective film.
Was deposited to 800 Å.

The magnetization of this FeRh sample was measured using an oscillating sample magnetometer while applying an external magnetic field.
At the time of measurement, use a rotary pump to measure the sample at 1 × 10 ^-3 P
While reducing the pressure to a, the sample was heated to raise its temperature from room temperature to 500 ° C. This FeRh sample reversibly undergoes a magnetic phase transition from antiferromagnetism to ferromagnetism. Magnetization abruptly occurred at about 130 ° C. when the temperature was raised, and the transition temperature was almost the same when the temperature was lowered. Moreover, Ir is added to FeRh
When 5 to 10% is added, the transition temperature rises by about 170 ° C to 280 ° C as compared with the case where no transition temperature is added, and when Pd is added to 2 to 6% relative to Rh, the transition temperature is not added. When compared to the transition temperature of about 50 ℃ ~
It decreased by 150 ° C. Further, the Rh composition of FeRh is set to 48 to 6
When changed in the range of 2%, the magnetic transition temperature increased with the increase of Rh. The Rh composition of FeRh is 50-60%
The range is suitable because a magnetic phase transition occurs during reproduction.

Next, using this FeRh as an intermediate layer, a magneto-optical recording medium of the present invention was prepared. First, in a DC magnetron sputtering device, Si, Gd, Tb, Fe,
Each target of Co and Rh is attached and the diameter is 130mm
The glass substrate with the pre-groove was fixed to a substrate holder installed at a position where the distance from the target was 150 mm, and then the chamber was evacuated to a high vacuum of 1 × 10 ⁻⁵ Pa or less with a cryopump. . After evacuation, Ar gas was introduced into the chamber until the pressure reached 0.4 Pa. Then, the SiN dielectric layer was set to 80 nm and GdFe was formed.
A Co reproduction layer having a thickness of 10 nm was formed. Then, an FeRh intermediate layer was formed by depositing FeRh on the substrate to a thickness of 5 nm. Then, a TbFeCo recording layer having a thickness of 15 nm, a SiN interference layer having a thickness of 30 nm, and an Al reflecting layer having a thickness of 60 nm were sequentially formed to obtain a magneto-optical recording medium of the present invention having the structure shown in FIG. 1B. At the time of forming each SiN dielectric layer, N ₂ gas was introduced in addition to Ar gas, and reactive sputtering was performed so that the refractive index was 2.2 while adjusting the mixing ratio thereof.

The composition of the GdFeCo reproducing layer is RE at room temperature.
It was rich and the compensation temperature was set to the Curie temperature or higher, and the Curie temperature was set to 300 ° C. or higher. FeR
The magnetic phase transition temperature of the intermediate layer was about 160 ° C.

The composition of the TbFeCo recording layer is TM at room temperature.
The rich and Curie temperatures were set to 250 ° C.

Then, the magneto-optical recording medium was rotated at a rotation speed of 26.
When rotated at 00 rpm, the R of 12.5 MHz was set at a position of radius 37 mm so that the recording mark length became 0.40 μm.
An F signal and an RF signal of 6.4 MHz were written so that the recording mark length was 0.78 μm. The linear velocity of the medium at this time is 10 m / s. After that, the C / N at each mark length was measured. The NA of the objective lens of the optical head was 0.55, and the laser wavelength was 780 nm.

Next, the linear velocity is set to 5 m / s (rotational speed 1300 r
pm, radius 37 mm, 15 m / s (rotation speed 3600)
rpm, radius 40 mm, 20 m / s (rotation speed 360
0 rpm, radius 54 mm, 25 m / s (rotation speed 39
80 rpm, radius 60 mm) in steps to obtain a mark length of 0.78 μm, 3.2 MHz, respectively.
Record signals of 9.6MHz and 12.8MHz, C / N
Then, the minimum recording power Pw that gives 48 dB was obtained. The reproduction power was set to a value (2.0 to 2.5 mW) that maximizes the C / N ratio at each recording power.

Next, the recording / reproducing characteristics were measured using this magneto-optical recording medium. The results are shown in Table 1.

(Example 2) Using the same film forming apparatus and film forming method as in Example 1, a SiN dielectric layer of 80 nm, a GdFeCo reproducing layer of 12 nm and Fe were similarly formed on a polycarbonate substrate.
RhIr intermediate layer 6 nm, TbFeCo recording layer 10 n
m, SiN interference layer 30 nm, Al reflective layer 60 nm,
Films were formed in order, and a magneto-optical recording medium of the present invention having the structure shown in FIG. 1B was obtained.

The composition of the GdFeCo reproducing layer is TM at room temperature.
The Curie temperature was set to be rich and 300 ° C. or higher.

The composition of the FeRh intermediate layer is Fe47 (Rh
The magnetic phase transition temperature of 95Ir5) 53 was about 150 ° C. The composition of the TbFeCo recording layer is RE rich at room temperature,
The compensation temperature was set to a Curie temperature or higher and a Curie temperature of 250 ° C.

Then, using this magneto-optical recording medium, recording and reproducing characteristics were measured in the same manner as in Example 1. The results are shown in Table 1.

(Embodiment 3) Using the same film forming apparatus and film forming method as in Embodiment 1, a SiN dielectric layer of 80 nm, a GdFeCo reproducing layer of 10 nm, and Fe were similarly formed on a polycarbonate substrate.
Rh intermediate layer is 5 nm, DyFeCo recording layer is 12 nm,
An SiN interference layer having a thickness of 30 nm and an Al reflection layer having a thickness of 60 nm were sequentially deposited to obtain a magneto-optical recording medium of the present invention having the structure shown in FIG. The composition of the GdFeCo reproducing layer is R at room temperature.
The E-rich and compensation temperatures were set to be the Curie temperature or higher and the Curie temperature 300 ° C. or higher.

The magnetic phase transition temperature of the FeRh intermediate layer is about 14
It was 0 ° C.

The composition of the DyFeCo recording layer was TM at room temperature.
The Curie temperature was set to be rich and 250 ° C.

Then, using this magneto-optical recording medium, recording and reproducing characteristics were measured in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1) A SiN dielectric layer 80 nm, a TbFeCo recording layer 80 nm and a SiN protective layer 70 nm were sequentially formed on a polycarbonate substrate in the same manner by using the same film forming apparatus and film forming method as in Example 1. As a film, a conventional magneto-optical recording medium which is not super-resolution is obtained. The refractive index of each SiN layer is 2.1.
And

The composition of the TbFeCo recording layer was TM at room temperature.
The Curie temperature was set to be rich and 250 ° C.

Next, using this magneto-optical recording medium, recording and reproducing characteristics were measured in the same manner as in Example 1. The results are shown in Table 1.

With this conventional medium, the super-resolution effect was not obtained.

COMPARATIVE EXAMPLE 2 Using the same film forming apparatus and film forming method as in Example 1, a SiN dielectric layer of 80 nm, a GdFeCo reproducing layer of 30 nm, and Tb were similarly formed on a polycarbonate substrate.
FeCo intermediate layer is 10 nm, TbFeCo recording layer is 40 nm
nm and a SiN protective layer having a thickness of 70 nm were sequentially formed to obtain a conventional super-resolution magneto-optical recording medium. The refractive index of each SiN layer was 2.1.

The composition of the GdFeCo reproducing layer is TM at room temperature.
The Curie temperature was set to be rich and 300 ° C. or higher. The composition of the TbFeCo intermediate layer was set to be TM rich at room temperature and a Curie temperature of 140 ° C.

The composition of the TbFeCo recording layer was TM at room temperature.
The rich and Curie temperatures were set to 250 ° C.

Next, using this magneto-optical recording medium, recording and reproducing characteristics were measured in the same manner as in Example 1. Further, only in Comparative Example 2, a reproducing magnetic field of 500 Oe was applied during reproducing. The results are shown in Table 1.

Comparing the results of Comparative Examples 1 and 2 with the results of Examples 1 to 3, the magneto-optical recording medium of the present invention has a C / N ratio of 0.4 μm even when the thickness of the magnetic layer is small. Four
It can be seen that super-resolution recording / reproduction of 5 dB or more is possible, and the laser power required for recording does not become as large as that of the comparative example even at a high linear velocity. Further, since the maximum output of the semiconductor laser used in the existing magneto-optical recording device on the surface of the medium plate is about 10 mW, the linear velocity possible in the conventional magneto-optical recording medium of the comparative example is 17 m / s at the maximum. However, in the embodiment of the present invention, the linear velocity can be improved up to about 25 m / s, and when the output of the semiconductor laser is further improved, the difference in the recording sensitivity between the present invention and the conventional example tends to become wider. I know there is. Therefore, it is understood that the magneto-optical recording medium of the present invention can achieve high-speed recording as compared with the conventional example.

[0068]

[Table 1]

[0069]

By using the magneto-optical recording medium and the recording / reproducing method of the present invention, the magnetic super-resolution can be realized by the magneto-optical recording medium in which the all-magnetic layer is made thin, and high-speed recording can be performed at a low material cost. It is possible to provide a density magneto-optical recording medium and an information reproducing / recording method.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a film structure of a medium of the present invention,
(A) is a figure of the basic composition of the medium of the present invention, and (b) is a figure showing the composition of an example of the medium of the present invention.

FIG. 2 is an explanatory view showing a magneto-optical reproducing method of the present invention,
(A) is a diagram showing an aperture and a mask in a light spot, (b) is a diagram showing a film structure and a magnetization state during reproduction of an example of the magneto-optical recording medium of the present invention, and (c) is a medium during reproduction. It is the figure which showed the temperature distribution of.

3A and 3B are explanatory diagrams showing a conventional super-resolution magneto-optical reproducing method, FIG. 3A is a diagram showing an aperture and a mask in a light spot, and FIG. 3B is a film structure of a conventional magneto-optical recording medium. FIG. 3C is a diagram showing a magnetization state during reproduction, and FIG. 6C is a diagram showing a temperature distribution of the medium during reproduction.

[Explanation of symbols]

 1 reproducing layer 2 auxiliary layer 3 intermediate layer 4 recording layer 7 light beam 9 medium moving direction 10 light beam 11 reproducing magnetic field applying direction 12 initializing magnetic field applying direction

Claims (6)

[Claims] 1. A first device comprising at least a perpendicular magnetization film.
A magnetic layer, a second magnetic layer, and a third magnetic layer are laminated on the substrate in the order of the first magnetic layer, the third magnetic layer, and the second magnetic layer from the light incident surface, and the first magnetic layer and the second magnetic layer. In the state where the magnetic layers are exchange-coupled, the directions of the entire magnetization are antiparallel, and the three magnetic layers have a temperature higher than room temperature (referred to as magnetic transition temperature) at which reversible transition from antiferromagnetism to ferromagnetism occurs. The first magnetic layer and the second magnetic layer are magnetostatically coupled to each other at room temperature, and the sublattice magnetic moments of these elements of the same kind are oriented in opposite directions at room temperature. Magneto-optical recording medium characterized in that sublattice magnetic moments of the same kind of elements in the first magnetic layer and the second magnetic layer are oriented parallel to each other by exchange coupling at a temperature above the layer transition to ferromagnetism. . 2. The magneto-optical recording medium according to claim 1, wherein the magnetic transition temperature of the third magnetic layer is a temperature around the transition temperature of the first magnetic layer to the perpendicular magnetization film. 3. The first magnetic layer and the second magnetic layer are made of a ferrimagnetic rare earth-iron group transition metal alloy, and are composed of a rare earth element-dominant magnetic layer at room temperature and an iron group transition metal-dominant magnetic layer at room temperature, respectively. The magneto-optical recording medium according to claim 1 or 2, wherein the third magnetic layer is a magnetic layer containing FeRh as a main component. 4. The surface of the second magnetic layer opposite to the light incident side,
A reflective layer made of metal is provided.
The magneto-optical recording medium according to any one of 1. 5. The magneto-optical recording medium according to claim 4, wherein an interference layer made of a dielectric material is provided between the second magnetic layer and the reflective layer. 6. The information recorded in the second magnetic layer according to claim 1.
6. The magneto-optical recording medium according to any one of 1 to 5 is irradiated with a light spot, and the third magnetic layer is anti-strengthen in a region where the temperature of the third magnetic layer is lower than the magnetic transition temperature in the region of the light spot. In the magnetic phase, the first magnetic layer and the second magnetic layer are magnetostatically coupled so that the sublattice magnetization directions of the first magnetic layer and the second magnetic layer are opposite to each other. In the region where the temperature of the layer is equal to or higher than the magnetic transition temperature, the third magnetic layer has a ferromagnetic phase, the first magnetic layer and the second magnetic layer are exchange-coupled, and the magnetization information of the second magnetic layer is changed by the magneto-optical effect. An information recording / reproducing method for a magneto-optical recording medium, which is converted into an optical signal and is read out as a recording signal.