JPH02278546A - Magneto-optical overwriting system - Google Patents

Abstract

PURPOSE:To simplify the constitution of a recording and reproducing device by providing a layer for suppressing mutual exchanging action between magnetic layers and setting the coercive force, Curie temperature and magnetization of each magnetic layer in specified relation. CONSTITUTION:Between first and second magnetic layers 3 and 5 and between the second and third magnetic layers 5 and 7, layers 4 and 6 are provided to prevent the mutual exchanging action between the magnetic layers. Coercive force Hc 1, Hc 2 and Hc 3 of these magnetic layers 3, 5 and 7 is set in the condition of Hc 3 > Hc 1 > Hc 2 at a room temperature and Curie temperatures Tc 1, Tc 2 and Tc 3 of these magnetic layers are set in the condition of Tc 1 < Tc 2 < Tc 3. The layer 7 can change the direction of the magnetization in the layer 5 at the room temperature. However, for the layer 3, the magnetization is provided so that the direction can not be changed. In such a magneto-optical recording medium PMM, a recording bias magnetic field in a conventional system is not required. Then, since the magnetization of the third magnetic layer is used for the initializing magnetic field of the second magnetic layer, the generating part of the magnetic field is not required and the constitution of the recording and reproducing device is simplified.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to magneto-optical overlay systems.

(Prior Art) Information is recorded in a magnetic layer of a magnetic recording medium by a change in magnetization corresponding to recorded information by utilizing changes in magnetic properties of a magnetic material due to heat. The magneto-optical recording and reproducing method uses optical effects associated with magnetism such as the Faraday effect and Kerr effect to read the state of change in magnetization corresponding to the recorded information in the magnetic layer. In recent years, many systems using various magneto-optical recording media have been proposed because their use enables high-density recording and reproduction.

Optical disk memory using a disc-shaped magneto-optical recording medium has been actively researched and developed as a large-capacity file that can be attached to and detached from a recording/playback device and is rewritable, and has been commercialized. However, at present, even though it is rewritable, the rewriting method is not simple and direct overwriting is not possible, so it has been widely used in the past. This has the disadvantage that it is less convenient to use than a so-called hard disk device (for example, a wintier-type disk device) in which the medium is not removable.

For this purpose, various types of magneto-optical overwriting methods have been proposed to enable direct overwriting of magneto-optical disks, but among the magneto-optical overwriting methods that have already been proposed, (1) The rotating magneto-optical recording medium is irradiated with a minute spot of constant light intensity, and the recording bias magnetic field strength is modulated depending on the information signal being recorded. Magneto-optical overwrite method (2) A first magnetic layer composed of an amorphous alloy of a heavy rare earth metal and a transition metal, and a second magnetic layer composed of an amorphous alloy of a heavy rare earth metal and a transition metal. The first magnetic layer and the second magnetic layer have a laminated structure in such a state that magnetic exchange interaction occurs between the two magnetic layers, and the coercive force Hcl of the first magnetic layer and the coercive force Hc of the second magnetic layer
2 is in the relationship Hc ], ) Hc 2 at room temperature, and the Curie temperature Tc of the first magnetic layer is
1 and the Curie temperature Tc2 of the second magnetic layer are Te1(T
A magneto-optical recording medium including a component made of a magnetic material having a relationship of c2, and a first magnetic layer in the magneto-optical recording medium described above are heated to a temperature equal to or higher than the Curie temperature Tcl. The first light intensity is such that the second magnetic layer is heated to a temperature below the Curie temperature TcZ, and the first magnetic layer in the magneto-optical recording medium has a Curie temperature. Temperature Tcl
The light intensity is modulated into a second light intensity that is heated to a temperature higher than the nearby temperature and the second magnetic layer is heated to a temperature higher than the temperature around the Curie temperature Tcz. means for condensing the laser beam and irradiating it onto the magneto-optical recording medium; means for relatively moving the focused point of the laser beam and the magneto-optical recording medium; Application of an external magnetic field for initialization of the second magnetic layer such that only the second magnetic layer is magnetized in a predetermined direction in its thickness prior to being irradiated by the laser beam; the first magnetic layer and the second magnetic layer by heating at the focal point by the laser beam having the second light intensity.
In the cooling process after the magnetization of both magnetic layers disappears, first, the above-mentioned second magnetic layer is applied to the above-described magnetization disappearing portion of the second magnetic layer. A second magnet in the opposite direction to the direction of magnetization in the magnetic layer.
A new magnetization is generated by an external bias magnetic field that generates a magnetic field capable of magnetizing the magnetic layer of the second magnetic layer, and then the newly generated magnetization of the second magnetic layer is transferred to the first magnetic layer by magnetic exchange interaction. After the magnetization of only the first magnetic layer has been extinguished by heating at the focal point by the laser beam having the first light intensity, In the cooling process, the magnetization of the second magnetic layer corresponding to the part where the magnetization disappears in the first magnetic layer changes due to magnetic exchange interaction to the magnetization of the first magnetic layer. An overwrite method using a magneto-optical recording medium equipped with an exchange two-layer film comprising means for generating magnetization in the erased portion and means for reproducing from the first magnetic layer side. There are two types of magneto-optical overwriting methods: .

(Problems to be Solved by the Invention) However, in the magneto-optical overwrite method shown in (1) of the conventional magneto-optical overwrite methods described above, the magnetic field is generated by the information signal to be recorded. For high-density recording, it is necessary to generate a high-frequency magnetic field that changes at a high frequency, but as is well known, it is difficult to generate a magnetic field of sufficient strength at high frequencies. Therefore, this (1
) The problem with the magneto-optical overwrite method is that it is difficult to increase the information transfer speed and it is not easy to realize high-density recording and reproduction.

In addition, in the above-mentioned (2) overwrite method using a magneto-optical recording medium equipped with an exchange two-layer film, the first magnetic layer and the second magnetic layer constituting the exchange two-layer film are , a means for applying an external magnetic field for initializing the second magnetic layer, and a means for applying a bias magnetic field necessary for recording, which are difficult to configure as having the necessary magnetic properties, respectively. The problem is that two external magnetic fields are often required, which increases the size of the device.

In the above-mentioned (2) overwriting method using a magneto-optical recording medium equipped with an exchangeable two-layer film, a high transfer speed can be obtained because the recording of information signals is performed by optical change stages. 2) Check the Curie point, compensation point, coercive force, magnetization, and film thickness of each magnetic layer for the first and second magnetic layers that make up the film. It is not easy to control the domain wall energy between the layers and the magnetic walls to configure each layer to have the necessary magnetic properties, and there are problems with productivity and reproducibility. This also has the disadvantage of increasing the size of the device.

Next, in the above-mentioned (2) overwrite method using a magneto-optical low recording medium having two exchange layers and one layer.

The difficulty in configuring the exchange two-layer films in a magneto-optical recording medium so that they each have the necessary magnetic properties will be explained with reference to FIG. 3 as follows.

That is, overwriting using a magneto-optical recording medium equipped with an exchange two-layer film! The coercive force of the first magnetic layer at room temperature is expressed as l-1 in the first magnetic layer and the second magnetic layer constituting the exchange two-layer film of the magneto-optical recording medium used in the method.
c1, the Curie point is Tc1, the coercive force of the second magnetic layer at room temperature is Hc2, and the Curie point is Tc2, the relationship shown in the following equations (1) and (2) is Hcl > Hc2 (1) Tc1 < The first magnetic layer and the second magnetic layer described above are made of a magnetic material having magnetic properties such that Tc2 (2) holds true.

By the way, the first magnetic layer is made of an amorphous alloy of a heavy rare earth metal (RE) and a transition metal (TM), and the first magnetic layer is made of an amorphous alloy of a heavy rare earth metal (RE) and a transition metal (TM). When the two magnetic layers are laminated together with the second magnetic layer, the reversal magnetic field of each of the magnetic layers described above is caused by the exchange interaction of the two magnetic layers, so that the two magnetic layers are independently activated. This will be different from the reversal magnetic field if it exists.

For example, the magnetic hysteresis characteristics in the state where the first magnetic layer composed of an amorphous alloy of heavy rare earth metal (RE) and transition gold@(TM) exists alone are shown in Fig. 3 (
b), and the magnetic hysteresis in the state where the second magnetic layer composed of an amorphous alloy of heavy rare earth metal (RE) and transition gold i (TM) exists alone. Assuming that the characteristics are as shown in FIG. 3(a), the magnetic hysteresis characteristic of the laminate when the first magnetic layer and the second magnetic layer described above are laminated is the third one. The reversal magnetic field of the first magnetic layer, as shown by (c) in the figure, is shown in (b) of Figure 3 when the first magnetic layer exists alone. Hc is smaller than 1, and the reversal magnetic field of the second magnetic layer is smaller than Hc2 shown in FIG. 3(a) when the second magnetic layer exists alone. Therefore, the following equations (2) and (3) hold true.

H1=Hcl-crw/2M5ltL-(2)H
2=Hc2 +σv/2M52t2 - (3) (where, L1 and t2 are the film thicknesses of each magnetic layer, and σ is the interfacial domain wall energy) And an overwrite method using a magneto-optical recording medium equipped with an exchange two-layer film In this case, the initialization magnetic field Hini is the reversal magnetic field H1, which is shown in equations (2) and (3) above.
, H2 must satisfy the condition of the following equation (4).

Hl>Hinj>H2−・=(4) However, the magnitude of the switching magnetic fields H1 and H2 is (2).

As shown in equation (3), the film thickness t1 of each magnetic layer,
t2, interfacial domain wall energy σ, etc., in order to set the magnitudes of the reversal magnetic fields H1 and H2 so as to satisfy the condition of equation (4), it is necessary to It is necessary to accurately control coercive force Hc], I-Ic2, saturation magnetization Ms], Ms2, film thicknesses t1, t2, etc., but this is extremely difficult.

As a magneto-optical overwrite method 1~ that does not have the problems that have arisen in the previously proposed magneto-optical overwrite methods described in (]) and (2), the applicant company has previously proposed the following methods:
A first magnetic layer made of an amorphous alloy of a heavy rare earth metal and a transition metal, and a second magnetic layer made of an amorphous alloy of a heavy rare earth metal and a transition metal are combined with the first magnetic layer described above. The first magnetic layer and the second magnetic layer have a laminated structure with a layer interposed therebetween to prevent magnetic exchange interaction between the first magnetic layer and the second magnetic layer. The term "layer" means that the coercive force Hc of the first magnetic layer and the coercive force Hc2 of the second magnetic layer have a relationship of Hcl>Hc2 at room temperature and in odor, and the Curie temperature T of the first magnetic layer is
c1 and the Curie temperature Tc2 of the second magnetic layer are Te1(
Magneto-optical recording having a component made of a magnetic material which has a relationship of Tc2 and which, at least for the second magnetic layer, does not have a compensation point between the room temperature and the Curie temperature. The medium and the first magnetic layer in the magneto-optical recording medium have a Curie temperature Tc1.
a first light intensity that is heated to a temperature above the nearby temperature and a second magnetic layer heated to a temperature below a temperature near the Curie temperature Tc2; and the above-mentioned magneto-optical recording medium. The first magnetic layer at
The light intensity is modulated to a second light intensity that is heated to a temperature higher than or equal to a temperature near c1 and a second light intensity that is brought into a heating state such that the second magnetic layer is heated to a temperature higher than or equal to a temperature near Curie temperature Tc2. means for condensing the laser beam and irradiating it onto the magneto-optical recording medium; means for relatively moving the focal point of the laser beam and the magneto-optical recording medium; means for applying an external magnetic field for magnetizing only the second magnetic layer in a predetermined direction in the thickness direction of the second magnetic layer before being irradiated with the laser beam having a second intensity; In the cooling process after the magnetization of both the first and second magnetic layers disappears due to heating at the focal point by the light flux, first, the above-described magnetization in the second magnetic layer disappears. A demagnetizing field from around the part where the magnetization disappears in the second magnetic layer causes new magnetization in the opposite direction to that of the surrounding area, and then
In the part where the magnetization disappears in the magnetic layer, the second
After the magnetization is caused by the transfer of the newly generated magnetization in the magnetic layer of In the cooling process, the magnetization of the second magnetic layer corresponding to the part where the magnetization disappears in the first magnetic layer is transferred to the part where the magnetization disappears in the first magnetic layer. The present invention provides a magneto-optical overwrite system comprising means for controlling the magnetic layer, and means for performing reproduction from the first magnetic layer side.

(Problems to be Solved by the Invention) The magneto-optical overlay methods 1 to 1 proposed by the applicant company described above do not require the recording bias magnetic field required in the conventional method, and furthermore, the initialization Since the magnetic field generating section can be provided anywhere other than the irradiation position of the recording laser beam, this has the advantage that the configuration of the recording/reproducing device can be easily simplified. In the magneto-optical overwrite method proposed by the applicant company, even if the initialization magnetic field generation part can be provided anywhere other than the irradiation position of the recording laser beam, Since a device for generating an initializing magnetic field was required, it was inevitable that the structure of the device would become larger.

(Means for Solving the Problems) The present invention provides a first metal alloy composed of an amorphous alloy of a heavy rare earth metal and a transition metal. 2. A third magnetic layer is provided between the first magnetic layer and the second magnetic layer, and between the second magnetic layer and the third magnetic layer, respectively. The coercive forces of the first and second magnetic layers are Hc1 and Hc2, respectively.
When the coercive force Hc1 of the first magnetic layer and the coercive force Hc2 of the second magnetic layer are Hcl) Hc at room temperature
2, and the Curie temperature Tc1 of the first magnetic layer, the Curie temperature Tc2 of the second magnetic layer, and the Curie temperature Tc3 of the third magnetic layer are Te1(Tc2(
Furthermore, for at least the second magnetic layer, a magnetic material that does not have a compensation point between room temperature and the Curie temperature is used, and furthermore, the above-mentioned third The magnetic layer is a magnetic material having magnetic properties such that the direction of magnetization of the second magnetic layer can be changed at a temperature below the Curie temperature of the first magnetic layer, but the direction of magnetization of the first magnetic layer cannot be changed. is used, and the first magnetic layer in the magneto-optical recording medium described above is heated to a temperature higher than the temperature near the Curie temperature Tc1, and the second magnetic layer is heated to a temperature near the Curie temperature Tc2. The first light intensity is heated to a temperature below, and the first light intensity in the magneto-optical recording medium is
The second magnetic layer is heated to a temperature higher than the temperature near the Curie temperature Tc1, and the second magnetic layer is heated to a temperature higher than the Curie temperature Tc1.
a second light intensity that is heated to a temperature near c2, a means for condensing a laser beam whose light intensity is modulated and irradiating the magneto-optical recording medium, and the laser beam as described above. The bimagnetism of the first magnetic layer and the second magnetic layer is achieved by means of relatively moving the focal point of the laser beam and the magneto-optical recording medium, and by heating the focal point with a laser beam having a second light intensity. In the cooling process after the magnetization of the layer disappears, first, the demagnetizing field from around the area where the magnetization disappears in the second magnetic layer is applied to the area where the magnetization disappears in the second magnetic layer. A new magnetization in the opposite direction is generated, followed by the first magnetization.
In the part where the magnetization disappears in the magnetic layer, the second
After the magnetization is caused by the transfer of the newly generated magnetization in the magnetic layer of In the cooling process, the magnetization of the second magnetic layer corresponding to the part where the magnetization disappears in the first magnetic layer is transferred to the part where the magnetization disappears in the first magnetic layer. a magneto-optical overcoat comprising: means for initializing the second magnetic layer by magnetization of the third magnetic layer at room temperature; and means for reproducing from the first magnetic layer side. This provides a write method.

(Function) Each of the first and second elements is composed of an amorphous alloy of a heavy rare earth metal and a transition metal. Second. A magnetic exchange effect is exerted between the third magnetic layer, the first magnetic layer and the second magnetic layer, and the second magnetic layer and the third magnetic layer. The coercive forces Hc1 and Hc2 of the first and second magnetic layers J3 are such that the coercive forces Hc1) Hc2 at room temperature are have a relationship, and
The Curie temperature 'rcl of the first magnetic layer, the Curie temperature Tc2 of the second magnetic layer, and the Curie temperature -fc3 of the third m-layer have the relationship Tc1 (Tc2 (goc3)). Furthermore, for at least the second magnetic layer, a magnetic material that does not have a compensation point between room temperature and the Curie temperature is used, and furthermore, the third magnetic layer described above is arranged to compensate for the curve of the first magnetic layer. Although the direction of magnetization of the second magnetic layer can be changed at a temperature of less than 1゛c1,
A magneto-optical recording medium is used in which a magnetic material having magnetic properties that does not change the direction of magnetization of the magnetic layer is used, and the first magnetic layer in the magneto-optical recording medium is heated to a temperature near the Curie temperature 'rcl. The first light intensity is heated to the above temperature and the second magnetic layer is heated to a temperature r near the Curie temperature TcZ, and the first light intensity is A second light intensity that heats the first magnetic layer to a temperature equal to or higher than the Curie temperature Tc1 and heats the second magnetic layer to a temperature near the Curie temperature Tc2. Recording is performed by condensing a laser beam whose light intensity is modulated and irradiating it onto a magneto-optical recording medium.

During recording, when heated at the focal point by the laser beam of the second light intensity, in the cooling process after the magnetization of both the first and second magnetic layers disappears, , new magnetization in the opposite direction to the surroundings is generated in the above-mentioned part of the second magnetic layer where the magnetization disappears due to the demagnetizing field from around the part where the magnetization disappears in the second magnetic layer. Magnetization is generated in the portion of the magnetic layer where the magnetization disappears by transferring the magnetization newly generated in the second magnetic layer.

Furthermore, in the case where recording is performed by heating at a condensing point by a laser beam having the first light intensity, the first magnetic layer described above is The magnetization of the second magnetic layer corresponding to the portion where the magnetization disappears is transferred to the portion where the magnetization disappears in the first magnetic layer.

The magnetization of the third magnetic layer at room temperature causes the initialization magnetic field to initialize the second magnetic layer.

(Example) Hereinafter, specific contents of the magneto-optical overwriting method of the present invention will be explained in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a schematic configuration of a recording/reproducing apparatus, FIG. 2 is a schematic cross-sectional view of a magneto-optical recording medium used in the magneto-optical overwriting method of the present invention, and FIG. 4 and 5 are side views of the magnetic characteristics of each magnetic layer.

Magneto-optical overlay 1 of the present invention whose schematic configuration is shown in FIG.
~ In the block diagram of the system, Md is a drive motor, 9 is a rotating shaft, ] 0 is a turntable, PMM is a magneto-optical recording medium whose specific configuration is shown in Figure 2, C is a clamper, and Pfl is a laser. Luminous flux, L is objective lens (condensing lens)
, P, Q a are laser beams condensed by a condensing lens L, and the magneto-optical recording medium PMM is placed on the turntable 10 and then fixed by a clamper C, and the drive motor Md is rotated at a predetermined speed. It is rotated integrally with the turntable 10 by being rotationally driven in the direction of arrow R in the figure.

The laser beam PQ described above is emitted from a laser light source (not shown) provided in an optical head (optical pickup) including the condensing lens L described above, and is emitted from an optical system (not shown). The laser beam PQa, which is focused by the condensing lens L of the optical head, is formed when the optical head moves in a direction perpendicular to the extending direction of the recording trace on the magneto-optical recording medium PMM during recording and reproducing operations. By moving in a predetermined movement manner, the light is focused on the magneto-optical recording medium PMM as a light spot with a minute diameter.

During the recording operation, the energy of the laser beam is changed in a predetermined manner as described below depending on the content of the recording,
Further, during the reproduction operation, the energy is constant and smaller than that during the recording operation.

FIG. 2 is a schematic cross-sectional view of a magneto-optical recording medium used in the magneto-optical overwriting method of the present invention. In FIG. 2, 1 is a transparent substrate, and 2 is an intermediate layer (car enhancement/protective layer). 3 is a first magnetic layer composed of an amorphous alloy of a heavy rare earth metal and a transition metal, and 5 is a second magnetic layer composed of an amorphous alloy of a heavy rare earth metal and a transition metal. magnetic layer.

Further, 4 is a layer for preventing magnetic exchange interaction from occurring between the first magnetic layer 3 and the second magnetic layer 5, and 7 is an amorphous layer of heavy rare earth metal and transition metal. 6 is a layer for preventing magnetic exchange interaction from occurring between the second magnetic layer 5 and the third magnetic layer 7; 8 is a third magnetic layer made of a magnetic alloy; It is a protective layer.

The intermediate layer 2 and the protective layer 6 described above are not necessary components in principle in the operation of overwriting a magneto-optical recording medium by the magneto-optical overwriting method of the present invention, but they are This is a component that should be included in the configuration when a magnetic recording medium is put into practical use.

In the magneto-optical overwrite method of the present invention, in the magneto-optical recording medium having the configuration shown in FIG. 2 used during recording and reproduction, the first magnetic layer 3 and the second magnetic layer 5 described above are and the third magnetic layer 7 means the first magnetic layer 3
The coercive force Hcl of the second magnetic layer 5, the coercive force Hc2 of the second magnetic layer 5, and the third
The coercive force Hc3 of the magnetic layer 7 is Hc3 at room temperature.
) Hc 1 > Hc 2, and the Curie temperature Tc1 of the first magnetic layer 3, the Curie temperature 1゛C2 of the second magnetic layer 5, and the Curie temperature Tc3 of the third magnetic layer 7. are in the relationship Tc1<Tc2<Tc3, and at least the second magnetic layer 5 is constructed using a magnetic material that does not have a compensation point between room temperature and the Curie temperature. FIGS. 4 and 5 show side views of the magnetic characteristics of each of the first to 33rd magnetic layers.

Further, the third magnetic layer 7 described above has such a magnetization that the direction of magnetization of the second magnetic layer 5 can be changed at room temperature, but the direction of magnetization of the first magnetic layer 3 cannot be changed. At the same time, at an information recording temperature higher than room temperature, the first
A magnetic material is used that has magnetic properties that exhibit magnetization that does not affect the magnetic layer 3 and the second magnetic layer 5.

In the magneto-optical overwriting method of the present invention, a magneto-optical recording medium having the configuration shown in the second figure used during recording and reproduction, that is, a transparent plastic substrate is used as a transparent substrate 1.
, each of the above-mentioned constituent parts 2 to 8 is placed on the transparent substrate 1.
Table 1 below shows a specific example of the structure of a magneto-optical recording medium in which each layer is sequentially formed.

(Table 1) In the specific configuration example of the magneto-optical recording medium shown in Table 1 above, there is no magnetic exchange interaction between the first magnetic layer 3 and the second magnetic layer 5. The layer 4 provided to prevent magnetic exchange and the layer 6 provided to prevent magnetic exchange interaction from occurring between the second magnetic layer 5 and the second magnetic layer 7 are made of non-magnetic material. The thickness is 5 depending on the body material tantalum.
nm film is used.

As described above, in the magneto-optical recording medium used in the magneto-optical overwriting method of the present invention, the amphiphilic layers 3 and 5 are provided between the first magnetic layer 3 and the second magnetic layer 5. A layer 4 is provided to prevent exchange interactions from occurring,
Further, since a layer 6 is provided between the second magnetic layer 5 and the third magnetic layer 7 to prevent the exchange interaction between the amphiphilic layers 5 and 7 from reaching the above-mentioned The reversal magnetic field of each magnetic layer 3, 5.7 is approximately equal to that when each magnetic layer 3, 5.7 exists independently.

Therefore, in the magneto-optical recording medium used in the magneto-optical overwriting method of the present invention, the initializing magnetic field H is used to invert only the second magnetic layer 5.
o is given by the following ( 5) A magnetic field that satisfies the relationship of formula % formula (5), that is, the coercive forces Hc1 and HO2 in each of the magnetic layers 3 and 5 when the above-mentioned amphiphilic layers 3 and 5 exist individually, respectively. A magnetic field between the two is sufficient.

The above points obtained in the magneto-optical overwriting method of the present invention are obtained by the exchange 2 described above with reference to equations (2) to (4).
The setting of the initialization magnetic field Hjnj in the conventional overwrite method using a magneto-optical recording medium with a layered film is
Regarding the reversal magnetic fields H1 and H2 in the layer film, Hl>Hjni>H2・44) Since the condition of equation (4) must be satisfied,
In order to set the magnitudes of the reversal magnetic fields H1 and H2 so as to satisfy the condition of equation (4) described above, the coercive forces Hc1 and Hc2 of each layer and the saturation magnetization M s 1.
, M s 2, film thickness t 1. This is a great advantage in manufacturing the magneto-optical recording medium and in the configuration of the recording/reproducing device, compared to the case where it was necessary to accurately control t2 and the like.

In addition, in the magneto-optical recording medium used in the magneto-optical overwriting method of the present invention, the first magnetic layer 3, the second magnetic layer 5, and the third magnetic layer 7 are different from each other. The coercive force Hcl of 3, the coercive force Hc2 of the second magnetic layer 5, and the coercive force Hc3 of the third magnetic layer 7 are HO3) Hcl at room temperature.
) I(c2, and the above-mentioned Curie temperature Tc1 of the first magnetic layer 3, Curie temperature 'I''c2 of the second magnetic layer 5, and Curie temperature 'r of the third magnetic layer 7
c3 has the relationship T"cl (Tc2 < Tc3, and at least the second magnetic layer 5 is constructed using a magnetic material that does not have a compensation point between room temperature and the Curie temperature, and the above-mentioned The third magnetic layer 7 has a magnetization that can change the direction of magnetization of the second magnetic layer 5 at room temperature Tr, but cannot change the direction of magnetization of the first magnetic layer M3, and At the information recording temperature T1, 'I'2 (see Figure 3), which is higher than the room temperature Tr, the magnetic layer 3 exhibits such magnetization that it does not affect the second magnetic layer 3 and the second magnetic layer 5. The third magnetic material P17 has a very large coercive force (Tc3) so that magnetization is always maintained in a certain direction at room temperature Tr. 3 magnetic layer 7
The magnetic field (HO) generated by the magnetization of the third magnetic layer 7 changes the direction and orientation of the magnetization of the adjacent second magnetic layer 5.
The third magnetic layer 7 has a magnetization strength such that the direction of magnetization is directed to There is no need to provide a separate means for applying an external magnetic field, which was conventionally required, in order to apply an initial magnetization field to the magneto-optical recording medium PMM.

Next, in the magneto-optical overwriting method of the present invention, a magneto-optical recording medium (a disc-shaped magneto-optical recording medium, hereinafter also referred to as a disk) having the configuration described with reference to FIG. A case will be described in which recording and reproducing is performed by rotating the PMM in the direction of arrow R at a predetermined rotation speed under the control of a rotation control circuit (not shown) by the drive motor Md described above.

The condensing lens L condenses the laser beam PM emitted from a laser light source (not shown), and the condensed light PQa enters the disk PMM from the transparent substrate 1 side, and the first
．． A light condensing portion 11 is created by a minute light spot in the second magnetic layers 3 and 5.

As mentioned above, the third magnetic layer 7 can change the direction of magnetization of the second magnetic layer 5 at room temperature 1゛r, but cannot change the direction of magnetization of the first magnetic layer 3. The material has such a magnetization that it does not affect the first magnetic layer 3 and the second magnetic layer 5 at information recording humidity higher than room temperature T'r. A magnetic material having magnetic properties is used, and the third magnetic layer 7
At room temperature Tr, the coercive force Hc3 is very large so that magnetization is always maintained in a certain direction, and this third
The magnetic field (Ho) generated by the magnetization of the magnetic layer 7 changes the direction and orientation of the magnetization of the adjacent second magnetic layer 5 as described above.
Since the magnetic layer 7 has a magnetization strength that is made to be oriented in the same direction as the magnetization direction of the magnetic layer 7, the portion away from the light converging section 11 by the laser beam PQ emitted from the laser light source is The third magnetic layer 7 operates as an initial magnetization magnetic field application layer in the part where the temperature is at room temperature Tr, and the magnetic field (HO) generated by the magnetization of the third magnetic layer 7 causes the adjacent second magnetic layer to The magnetization direction and orientation of the magnetic layer 5 are made to match the magnetization direction and orientation of the third magnetic layer 7 described above.

As a result, the second temperature at room temperature Tr. third magnetic layer 5,
The state of magnetization of No. 7 is the state of magnetization of No. 2 in [1], f:6] in FIG.
Initialization caused by the magnetization of the third magnetic layer 7, as shown in the state of magnetization of the third magnetic layers 5 and 7 (arrows in FIG. 3 indicate the magnitude, direction, and direction of magnetization) Magnetic field (Ho
), only the second magnetic layer 5 is initially magnetized (perpendicular magnetization) in the direction of the magnetization of the third magnetic layer 7 described above in the direction of its thickness.

That is, the external magnetic field Ho generated in the third magnetic layer 7 is caused by the coercive force Hcl of the first magnetic layer 3 and the coercive force Hc2 of the second magnetic layer M5, which have a relationship of Hcl) Hc2 at room temperature Tr. On the other hand, at room temperature Tr, the following (5)
A magnetic field Ho satisfying the relationship of formula % formula % (5) :3] is applied to the second magnetic layer 5, and the second magnetic field Ho in the disk 7
Only the magnetic layer 5 is magnetized in the same magnetization direction and direction as that of the third magnetic layer 7 by the initialization Ha generated in the third magnetic layer 7 described above.

Next, the first . Second. In a state where the third magnetic layer 3, 5.7 is in the magnetized state illustrated in [1] in FIG.
The temperature of +517 is the Curie temperature Tc of the first magnetic layer 3.
1 with the relationship Tc3>Tc2>Tc1
A laser beam PIl having a power capable of heating the magnetic layer 3 to a Curie temperature Te1 or higher is focused PΩa to heat the first to third magnetic layers M3, 5.7 in the disk PMM, and the focused point is When the temperature of the first to third magnetic layers 3°5.7 corresponding to 11 is heated to a temperature equal to or higher than the Curie temperature Te1 of the first magnetic layer 5, the light condensing point] 1
The magnetization of the portion of the first magnetic layer 3 corresponding to the first magnetic layer 3 disappears, and the third
The state is as illustrated in [2] in the figure.

In the rotationally driven disk PMM, the first
~ As described above, when the third magnetic layer 3, 5.7 portion shifts from the position of the focal point 11 of the laser beam PQ as the disk PMM rotates and enters the cooling process, the temperature gradually decreases. The temperature rises due to the condensing point 11 of the laser beam pu, and the magnetization disappears. 1], the magnetic field caused by the magnetization of the second magnetic layer 5 causes magnetization in the same direction and direction as that of the second magnetic layer 5.

When the state of magnetization in the first magnetic layer 3 is an upward arrow, the recording state in the first magnetic layer 3 is defined as a recording state of (0); When the state of magnetization is indicated by a downward arrow, the first magnetic layer 3
If we define the recording state in (1) as the recording state in (1), then as mentioned above, the state of [1] in FIG. 3 changes from the state of [1] in FIG.
The recording state of the first magnetic layer 3, which is brought into the state []] in FIG. 3 after being brought into the state [2], is the recording state (0).

Next, the first . Second. In the state where the third magnetic layer 3, 5.7 is in the magnetized state illustrated in [1] in FIG. 3, the first to third magnetic layers 3
, 5.7, the Curie temperature Tc of the first magnetic layer 3
A laser beam PQ having a power capable of heating the second magnetic layer 5 to the Curie temperature Tc2 or higher, which has the relationship T"c3>T"c2>Tc1 with respect to ~Third magnetic layer 3, 5.7
Heat it up.

The condensing point] 1 and the corresponding first to third magnetic layers 3° 5.
7 is the Curie temperature Tc of the second magnetic layer 5 mentioned above.
When heated to 2 or more, the 1st. The magnetization of the second magnetic layers 3 and 5 disappears, and the third
The state is as illustrated in [3] in the figure.

In the rotationally driven disk PMM, the first
- When the third magnetic layer 3, 5.7 shifts from the focal point 11 of the laser beam PQ as the disk PMM rotates and enters a cooling process, the temperature gradually decreases. The temperature is equal to or lower than the Curie temperature Tc2 of the second magnetic layer 5, and the Curie temperature Te1 of the first magnetic layer 3
In the above temperature range, the portion of the second magnetic layer 5 where the magnetization has disappeared is affected by the demagnetizing field as indicated by the dotted line arrow in the figure due to the magnetization around that portion. As illustrated in Figure 3, downward magnetization occurs as indicated by the solid arrow.

That is, in the above state, the magnetization of the third magnetic layer 7 is small, so that the strength of the magnetic field generated by the magnetization of the third magnetic layer 7 is such that the above-mentioned magnetization of the second magnetic layer 5 disappears. a second magnetic layer 5 around the portion;
Since the strength of the demagnetizing field as indicated by the dotted line arrow in the figure is smaller than the strength of the demagnetizing field caused by the magnetization of A demagnetizing field as shown by the dotted arrow in the figure, which is generated by the magnetization around the magnet, causes downward magnetization as shown by the solid arrow, as illustrated in [4] of FIG.

In addition, as mentioned above, the Curie temperature T of the first magnetic layer 3
Since the second magnetic layer 5 having no compensation point between c1 and the Curie temperature Tc2 of the second magnetic layer is used, the operation described above can be performed reliably.

Next, when the temperature of the above-mentioned portion further decreases to below the Curie temperature Tcl of the first magnetic layer 3, the third
The second magnetic layer 5 is formed as described for [4] in the figure.
Due to the newly generated downward magnetization as indicated by the solid line arrow, downward magnetization as indicated by the solid line arrow as illustrated in [5] in FIG. 3 is generated in the first magnetic layer 3. The newly generated magnetization in the part of the first magnetic layer 3 where the magnetization disappears is generated in the second magnetic layer as described above, regardless of the magnetic field around the part of the first magnetic layer 3 where the magnetization disappears. What is caused by the newly generated magnetization in the F direction as shown by the solid arrow in 5 is that the magnetic moment of the second magnetic layer 5 is larger than the magnetic moment of the first magnetic layer 3 near the Curie temperature Tc1 or lower. This is because.

Then, the temperature of the above-mentioned portion further decreases to room temperature Tr.
3, the part of the second magnetic layer 5 that is magnetized downward as indicated by the solid line arrow becomes the third magnetic layer that functions as an initializing magnetic field generating part. The first to third magnetic layers 3, 5.7 in the disk PMM are initialized by the initialization magnetic field HO generated by the magnetization of the magnetic layer 7 of the disk PMM, and are magnetized upward as illustrated in [6] in FIG. The first magnetic layer 3 is brought into a state of magnetization such that
The magnetization state in is as indicated by the downward arrow, that is, the recording state in the first magnetic layer 3 is the recording state (1).

In this way, in the magneto-optical overwrite method of the present invention, it is possible to overwrite the disk PMM without using any bias magnetic field for the disk PMM, and there is no need to apply an initializing magnetic field from the outside.

(Effects of the Invention) As is clear from the above detailed explanation, the magneto-optical overlay 1 method of the present invention has first magneto-optical overlays each made of an amorphous alloy of a heavy rare earth metal and a transition metal. Second. A magnetic exchange action is applied between the third magnetic layer and the first magnetic layer and the second magnetic layer, and between the second magnetic layer and the third magnetic layer, respectively. The coercive forces of the first to third magnetic layers are set to Hc1, l-Tc2. When Hc3,
The coercive force Hc1 of the first magnetic layer, the coercive force Hc2 of the second magnetic layer, and the coercive force Hc3 of the third magnetic layer are Hc3 at room temperature.
) have the relationship Hc 1 > Hc2, and the Curie temperature Tc1 of the J-th magnetic layer, the Curie temperature Tc2 of the second magnetic layer, and the Curie temperature Tc of the third magnetic layer.
3 has the relationship Tc1 < Tc2 (Tc3, and furthermore, for at least the second magnetic layer, a magnetic material having no compensation point between room temperature and the Curie temperature is used, and furthermore, Further, the third magnetic layer described above has a magnetization that can change the direction of magnetization of the second magnetic layer at room temperature but cannot change the direction of magnetization of the first magnetic layer, and A magneto-optical recording medium using a magnetic material having magnetic properties that exhibits magnetization that does not affect the first and second magnetic layers at an information recording temperature higher than that of the first and second magnetic layers; The first magnetic layer in the magneto-optical recording medium has a Curie temperature Tc, 1
a first light intensity that is heated to a temperature above the nearby temperature and a second magnetic layer heated to a temperature below a temperature near the Curie temperature Tc2; and the above-mentioned magneto-optical recording medium. The first magnetic layer at
The light intensity is modulated to a second light intensity that is heated to a temperature higher than or equal to a temperature near c1 and a second light intensity that is brought into a heating state such that the second magnetic layer is heated to a temperature higher than or equal to a temperature near the Curie temperature TcZ. means for condensing the laser beam and irradiating it onto the magneto-optical recording medium; means for relatively moving the focal point of the laser beam and the magneto-optical recording medium;
The first beam is heated at the focal point by a laser beam with a light intensity of
In the cooling process after the magnetization of the inner magnetic layer between the magnetic layer and the second magnetic layer disappears, first, in the part of the second magnetic layer where the magnetization disappears, A demagnetizing field from around the area where the magnetization disappears creates new magnetization in the opposite direction to the surrounding area, and then new magnetization is generated in the area where the magnetization disappears in the first magnetic layer in the second magnetic layer. to generate magnetization by transferring the magnetization generated in
Furthermore, in the cooling process after only the magnetization of the first magnetic layer disappears due to heating at the focal point by the laser beam of the first light intensity, the magnetization of the first magnetic layer described above disappears in the cooling process. means for transferring the magnetization of the second magnetic layer corresponding to the section to the section where the magnetization disappears in the first magnetic layer; A magneto-optical overwrite system comprising means for initializing the layer and means for reproducing from the first magnetic layer side, which is used in the magneto-optical overwrite method 1 of the present invention. In the magneto-optical recording medium, there are gaps between the first magnetic layer 3 and the second magnetic layer 5, and between the second magnetic layer 5 and the third magnetic layer 7. Since the PIs 3 and 6 are provided to prevent the exchange interaction between the magnetic layers 3 and 5.
. The initialization field Ho to be used for inversion is Hc 1 at room temperature.
> Coercive force Hc of the first magnetic layer 3 in the relationship of Hc 2
At room temperature, Hcl > Ho > Hc2 (5
) The coercive force Hc 1 in each of the magnetic layers 3 and 5 in the case where the magnetic field satisfies the relationship of the above formula (5), that is, the above-mentioned inner magnetic layer 3.5 exists independently,
A magnetic field between Hc 2 is sufficient, and the above-mentioned points obtained in the magneto-optical overwriting method of the present invention are different from the conventional overwriting method using a magneto-optical recording medium equipped with an exchange two-layer film. Since the setting of the initialization magnetic field Hini in must satisfy the condition of equation (4) with respect to the reversal magnetic fields H1 and H2 in the exchanged two-layer film, Hl>Hjni>l-I2-(4),
In order to set the magnitudes of the reversal magnetic fields H1 and H2 so as to satisfy the condition of equation (4), the coercive forces Hc1 and Hc2 of each layer and the saturation magnetization M s 1 must be set.
, M s 2, film thickness t 1. This is a great advantage in manufacturing magneto-optical recording media and in the configuration of recording and reproducing devices, compared to the case where it was necessary to accurately control the magneto-optical overwrite of the present invention. This method does not require the recording bias magnetic field that is required during the recording operation in the conventional method, and furthermore, in the present invention, as the initialization magnetic field HO used for initializing the second magnetic layer 5, Since the magnetic field generated based on the magnetization of the third magnetic layer 7 at room temperature is used, there is no need to separately provide a generator for generating the initializing magnetic field, and the configuration of the recording/reproducing device can be simplified. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a recording/reproducing apparatus, FIG. 2 is a schematic cross-sectional view of a magneto-optical recording medium used in the magneto-optical overwriting method of the present invention, and FIG. FIGS. 4 and 5 are diagrams for explaining the operating principle of the magneto-optical overwrite method, and are side views of the magnetic characteristics of each of the first to third magnetic layers. DESCRIPTION OF SYMBOLS 1... Transparent substrate, 2... Intermediate layer, 3... First magnetic layer composed of an amorphous alloy of heavy rare earth metal and transition metal, 5... Heavy rare earth metal and transition metal A second magnetic layer made of an amorphous alloy, 4. A layer for preventing magnetic exchange interaction from occurring between the first magnetic layer 3 and the second magnetic layer 5, 7 ...a third magnetic layer composed of an amorphous alloy of a heavy rare earth metal and a transition metal,
6... A layer for preventing magnetic exchange interaction from occurring between the second magnetic layer 5 and the third magnetic layer 7, 8...
Protective layer, PMM7... magneto-optical recording medium (disc-shaped magneto-optical recording medium...disk), Md... drive motor, L
・Objective lens (condensing lens), PQ...laser beam,
PQa...Focused light, 9. Rotation axis, 10.. Turntable, C.. Clamper, 11.. Light condensing section. \t

Claims (1)

[Claims] The first, second, and third magnetic layers, each made of an amorphous alloy of a heavy rare earth metal and a transition metal, are arranged between the first magnetic layer and the second magnetic layer, and between the first magnetic layer and the second magnetic layer. The second magnetic layer and the third magnetic layer are sequentially laminated with a layer interposed therebetween to prevent the magnetic exchange action from occurring, and the first and third magnetic layers described above are When the coercive forces in the two magnetic layers are respectively Hc1 and Hc2, the coercive force Hc1 of the first magnetic layer and the coercive force Hc2 of the second magnetic layer have a relationship of Hc1>Hc2 at room temperature,
Further, it is assumed that the Curie temperature Tc1 of the first magnetic layer, the Curie temperature Tc2 of the second magnetic layer, and the Curie temperature Tc3 of the third magnetic layer have a relationship of Tc1<Tc2<Tc3, Furthermore, for at least the second magnetic layer, a magnetic material that does not have a compensation point between room temperature and the Curie temperature is used, and furthermore, the third magnetic layer described above is used.
The magnetic layer has magnetic properties such that the direction of magnetization of the second magnetic layer can be changed at a temperature below the Curie temperature of the first magnetic layer, but the direction of magnetization of the first magnetic layer cannot be changed. The magneto-optical recording medium in which the material is used and the first magnetic layer in the magneto-optical recording medium described above are heated to a temperature near the Curie temperature Tc1, and the second magnetic layer is heated to a temperature below the Curie temperature Tc2. The first light intensity is heated to a temperature such that the first magnetic layer in the magneto-optical recording medium has a Curie temperature Tc.
It is heated to a temperature higher than the temperature near 1 and the second
A second light intensity is brought into a heating state such that the magnetic layer is heated to a temperature higher than the Curie temperature Tc2, and a laser beam whose light intensity is modulated is focused onto a magneto-optical recording medium. means for irradiating, means for relatively moving the focal point of the laser beam and the magneto-optical recording medium; In the cooling process after the magnetization of both the second magnetic layer and the second magnetic layer disappears, first, the area around the area where the magnetization disappears in the second magnetic layer is A demagnetizing field from the magnetic field generates new magnetization in the opposite direction to the surroundings, and then the newly generated magnetization in the second magnetic layer is transferred to the part where the magnetization disappears in the first magnetic layer. Further, in the cooling process after only the magnetization of the first magnetic layer is extinguished by heating at the focal point by the laser beam having the first light intensity, the above-mentioned magnetization is caused in the cooling process. means for transferring the magnetization of the second magnetic layer corresponding to the magnetization disappearing portion of the first magnetic layer to the magnetization disappearing portion of the first magnetic layer; and a third magnetization at room temperature. means for initializing the second magnetic layer by magnetization of the layer;
a magneto-optical overwrite system comprising means for reproducing from the magnetic layer side of the