Abstract: A magneto-optical recording medium of the present invention has a recording layer made of a perpendicular magnetization film, and a readout layer which is in an in-plane magnetization state at room temperature and changes into a perpendicular magnetization state with a rise in temperature. When the magneto-optical recording medium is irradiated with a light beam, the readout layer separates into three regions: a region in an in-plane magnetization state, a region in a perpendicular magnetization state, and a region having a temperature not lower than the Curie temperature thereof. Only the region in the perpendicular magnetization state allows copying of the magnetization of the recording layer. Therefore, even when the diameter and intervals of recording bits on the recording layer are very small, it is possible to reproduce a target recording bit separately from a recording bit adjacent to the target recording bit.

Abstract: A method to produce a magneto-optical recording medium which includes a readout layer having in-plane magnetization at room temperature and in which a transition occurs from in-plane magnetization to a perpendicular magnetization when temperature rises, and a recording layer for storing information thereon magneto-optically. In the readout layer made of GdFeCo by adding Nd thereto, an amount of Nd to be added changes in a direction perpendicular to its film surface, and an amount of Nd is larger on a light incidence side than on the other side. As a result, even when a laser with a short wavelength is used, high density recording can be achieved as undesirable recording and reproducing operations due to a change in a magnetic interaction is prevented and also deterioration in quality of a reproducing signal is prevented.

Abstract: In a method for reproducing an optical disk of the present invention, address information of an optical disk, provided with tracking guides composed of (1) a wobbling groove wobbled in accordance with address information and (2) a normal groove which is not wobbled, is reproduced. The wobbling groove and the normal groove are alternately provided in a radius direction of the optical disk. When carrying out recording and reproducing of the optical disk, three beams composed of one main beam and two sub beams are used. The three beams are projected so that (a) the sub beams are respectively on the wobbling groove and the normal groove and (b) the main beam is on a land between the wobbling groove and the normal groove. The address information is found from reflected light of one of the sub beams. The above arrangement allows respective central portions of the sub beams to track the tracking guides.

Abstract: A magneto-optical recording medium having a substrate whereupon a transparent dielectric layer, a readout layer showing in-plane magnetization at room temperature and perpendicular magnetization with an increase in temperature, a metal film layer, a recording layer made of a perpendicularly magnetized film, and a protective layer are formed in this order, wherein the film thickness of the readout layer is between 5 nm and 30 nm, the film thickness of the metal film layer is between 6 nm and 40 nm, and the film thickness of the recording layer is between 20 nm and 80 nm. Since recording domain information at a portion showing in-plane magnetization is masked, even when adjacent recording bit enters into the beam diameter of a light beam focused, it is possible to separately reproduce individual recording bits with high signal quality.

Abstract: A magneto-optical recording medium includes a readout layer having in-plane magnetization at room temperature and in which a transition occurs from in-plane magnetization to a perpendicular magnetization when temperature rises, and a recording layer for storing information thereon magneto-optically. In the readout layer made of GdFeCo by adding Nd thereto, an amount of Nd to be added changes in a direction perpendicular to its film surface, and an amount of Nd is larger on a light incidence side than on the other side. As a result, even when a laser with a short wavelength is used, high density recording can be achieved as undesirable recording and reproducing operations due to a change in a magnetic interaction is prevented and also deterioration in quality of a reproducing signal is prevented.

Abstract: A magneto-optical recording medium has a transparent substrate, a first magnetic layer, first intermediate layer, a second magnetic layer, and a third magnetic layer provided in this order. The first magnetic layer has an in-plane magnetization at room temperature, while a transition from the in-plane magnetization to a perpendicular magnetization occurs to the first magnetic layer with a temperature rise. The first intermediate layer is made of a non-magnetic substance. The second magnetic layer is a film having a perpendicular magnetization. The third magnetic layer is a film having a perpendicular magnetization, has a coercive force smaller than that of the second magnetic layer at room temperature, and has a Curie temperature higher than that of the second magnetic layer.

Abstract: A magneto-optical recording medium includes a readout layer has in-plane magnetization at room temperature and in which a transition occurs from in-plane magnetization to perpendicular magnetization when temperature thereof is raised, and a recording layer for recording thereon information. The composition of the readout layer varies in a direction perpendicular to the surface thereof, and in the readout layer, the Co density on the light incident side is higher than the Co density on the interface between the readout layer and the recording layer. Therefore, the Curie temperature on the reproducing light incident side of the readout layer is high and the the polar Kerr rotation angle in reproducing increases, thereby achieving improvements in a reproducing signal quality.

Abstract: A magneto-optical recording medium is composed of a reproducing layer, a recording layer, and an initializing layer, which are laminated in this order. The reproducing layer is provided so that a light beam is projected thereon so as to reproduce information. The recording layer is provided so that information is recorded therein and the information is copied to the reproducing layer at a readout temperature. The initializing layer is provided so that the reproducing layer is initialized at room temperature. Non-magnetic layers are provided between the reproducing layer and the recording layer and between the recording layer and the initializing layer, respectively, so that such two layers are not exchange-coupled each other. The recording layer has a compensation temperature of room temperature, while the initializing layer has a compensation temperature of the readout temperature, which is achieved by temperature rise caused by the projection of the light beam.

Abstract: A magneto-optical recording medium has a recording layer whereon information is magneto-optically recorded. A readout layer is provided on the recording layer. The readout layer has a compensating temperature that is located between room temperature and the Curie temperature. In the readout layer, upon an application of a light beam, the in-plane magnetization occurs at room temperature and a transition from the in-plane magnetization to vertical magnetization occurs as the temperature of the irradiated area of the readout layer rises above a predetermined temperature. By employing this magneto-optical recording medium, with an application of a light beam that is intensity modulated into two levels, only a spot having a temperature not less than a predetermined temperature is involved in the reproduction; therefore, a recorded bit with a size smaller than the diameter of the light beam can be reproduced, thereby greatly increasing the recording density.

Abstract: A magneto-optical recording medium has an exchange-coupled triplilayer film wherein a readout layer which has in-plane magnetization at room temperature, and in which a transition occurs from in-plane magnetization to perpendicular magnetization when temperature thereof is raised above T.sub.1, an intermediate layer which has perpendicular magnetization at room temperature, the perpendicular magnetization being maintained from room temperature to Curie temperature T.sub.3, and a recording layer which has perpendicular magnetization at room temperature, the perpendicular magnetization been maintained from room temperature to Curie temperature T.sub.2 which are laminated in this order, and the temperatures T.sub.1, T.sub.2 and T.sub.3 satisfy the following inequality: T.sub.1 <T.sub.3 <T.sub.2.

Abstract: A transparent substrate of an optical memory is produced by injection molding using a stamper. Grooves and lands are alternately arranged on the optical memory, for tracking of light converged on the optical memory. The groove width is set in the range of 0.3 .mu.m to 0.4 .mu.m and the groove depth is set in the rage of 80 nm to 100 nm. A decrease in the width of a land at each edge is restrained to 0.2 .mu.m in maximum. With such dimensions, even when the track pitch is set to about 1.4 .mu.m, it is possible to obtain a track crossing signal with intensity sufficient for performing an access operation to a target track. Moreover, since the dimensions bring about an improved reflectance at a land, the optical memory achieves an improved C/N and recording density.

Abstract: The magneto-optical recording medium is provided with a readout layer which shows the in-plane magnetization and which changes from the in-plane magnetization to the vertical magnetization when its temperature rises higher than a predetermined temperature by irradiation of the light beam, a memory layer which records information thereon magneto-optically, an intermediate layer which keeps in-plane magnetization from room temperatures to its Curie temperature, and an writing layer which has a Curie temperature higher than that of the memory layer and has coercive force lower than that of the memory layer. Since the intermediate layer becomes a domain wall in optical modulation recording, it prevents the memory layer and the writing layer from forming a domain wall, so information can be recorded in good condition. Moreover, a portion of the readout layer besides a center portion of the light beam shows the in-plane magnetization and masks the memory layer at playback.

Abstract: A magneto-optical recording medium has magnetic multi-layers including a reproductive layer, which is a magnetic layer having perpendicular magnetic anisotropy, for reading out magneto-optically recorded information and a recording layer, which is a magnetic layer having perpendicular magnetic anisotropy, for magneto-optically recording information. In the magneto-optical recording medium, the following conditions are fulfilled:H.sub.C1 (ta)+.sigma.w(ta)/2M.sub.S1 (ta)h.sub.1<-H.sub.C1 (t)+.sigma.w(t)/2M.sub.S1 (t)h.sub.1, and40(nm).ltoreq.h.sub.1 .ltoreq.120(nm)where h.sub.1 is the thickness of the reproductive layer, H.sub.C1 (ta) is coercive force of the reproductive layer at room temperature (ta), M.sub.S1 (ta) is saturation magnetization of the reproductive layer, M.sub.S2 (ta) is saturation magnetization of the recording layer, .sigma.w(ta) is magnetic domain wall energy of the magnetic domain wall formed between said reproductive layer and the recording layer, H.sub.

Abstract: A magnetic recording medium having a recording layer made up of a ferrimagnetic material whose compensation temperature is included within room temperatures and an information recording-reproduction method using the magnetic recording medium. During recording, while a light beam is projected on the recording layer so as to raise the temperature of a recording portion, information is recorded by applying a signal magnetic field from a magnetic head. During reproduction, while a light beam is projected on a reproducing portion of the recording layer so as to raise the temperature thereof, information is reproduced by detecting leakage flux from the reproducing portion by the magnetic head. Thus, during reproduction, no magnetic flux is generated from other portions of the recording layer not irradiated by the light beam. With the arrangement, crosstalk due to leakage flux from adjoining tracks not irradiated by the optical beam can be eliminated.

Abstract: A magneto-optical recording medium comprising a readout layer and a recording layer has a relationship that an external magnetic field H1 is smaller than an external magnetic field H4, where the H1 is a minimum external magnetic field necessary to make a magnetization direction of the readout layer direct to the direction reverse to a magnetization direction of the recording layer substantially at the room temperature, and the H4 is a maximum external magnetic field necessary to make the magnetization direction of the readout layer direct to the direction same as the magnetization direction of the recording layer at an high temperature not lower than a predetermined temperature. Moreover, the magneto-optical disk is provided, between the readout layer and the recording layer, with an intermediate layer which inhibits an effective bias magnetic field from the recording layer to the readout layer at the room temperature.

Abstract: A magneto-optical memory device is provided with a base whereon a first magnetic film which exhibits in-plane magnetization at room temperature and exhibits perpendicular magnetization at above room temperature, a second magnetic film having its Curie temperature above room temperature; and a third magnetic film having its Curie temperature set above the Curie temperature of the second magnetic film, which exhibits perpendicular magnetization in a temperature range between room temperature and Curie temperature are laminated in this order. When recording, the temperature of the third magnetic film is raised to the vicinity of its Curie temperature, and information is recorded thereon by an external magnetic field. As the magnetization of the second magnetic film having a temperature rise above its Curie temperature disappears, an exchange coupling force is not exerted between the first magnetic film and the third magnetic film.

Abstract: A magneto-optical disk, which possesses a disc-shaped substrate and a recording layer composed of a perpendicular magnetization film that is formed on the substrate, characterized in having: an area wherein magnetic domains having an upward magnetization and magnetic domains having a downward magnetization are alternately aligned along at least one circuit of the disk, the area being formed on the recording layer, the length of the magnetic domains having the upward magnetization being virtually equal to the length of the magnetic domains having the downward magnetization. This invention also has a reproducing method which is characterized in that, when information is reproduced by projecting a light beam onto the magneto-optical recording disk, the intensity of the light beam is adjusted so as to maximize the amplitude of a reproduced signal that is obtained from the area.

Abstract: A transparent substrate of an optical memory is produced by injection molding using a stamper. Grooves and lands are alternately arranged on the optical memory, for tracking of light converged on the optical memory. The groove width is set in the range of 0.3 .mu.m to 0.4 .mu.m and the groove depth is set in the rage of 80 nm to 100 nm. A decrease in the width of a land at each edge is restrained to 0.2 .mu.m in maximum. With such dimensions, even when the track pitch is set to about 1.4 .mu.m, it is possible to obtain a track crossing signal with intensity sufficient for performing an access operation to a target track. Moreover, since the dimensions bring about an improved reflectance at a land, the optical memory achieves an improved C/N and recording density.

Abstract: A magneto-optical recording medium includes a readout layer has in-plane magnetization at room temperature and in which a transition occurs from in-plane magnetization to perpendicular magnetization when temperature thereof is raised, and a recording layer for recording thereon information. The composition of the readout layer varies in a direction perpendicular to the surface thereof, and in the readout layer, the Co density on the light incident side is higher than the Co density on the interface between the readout layer and the recording layer. Therefore, the Curie temperature on the reproducing light incident side of the readout layer is high and the the polar Kerr rotation angle in reproducing increases, thereby achieving improvements in a reproducing signal quality.

Abstract: A magneto-optical memory element has a multi-layer construction in the order from a side first receiving light from a light-source which includes a first transparent dielectric film, a rare earth transition metal alloy film, a second transparent dielectric film and a reflective film. The magneto-optical device uses circular dichroism effect of a magnetic mater for reading information. The rare earth transition metal alloy film has a refractive index represented by n.+-..DELTA.n wherein n=3.2-3.55i and .DELTA.n=0.05-0.03i. The thickness of film is about 18 to 46 nm. The second transparent dielectric film has a refractive index of 2.0.+-.0.2 and a film thickness of 80 to 108 nm.