Abstract: A light reflecting and heat dissipating material which is capable of reflecting light and dissipating heat transmitted thereto from a layer in contact with or adjacent to the material to cool the layer is composed of an alloy represented by formula (I):Ag.sub.x Pd.sub.1-x (I)wherein 0.6.ltoreq..times..ltoreq.0.85. An optical information recording medium for recording information, reproducing and erasing recorded information is composed of a substrate, a recording layer formed thereon and a light reflection and heat dissipation layer composed of the above light reflecting and heat dissipating material formed on the recording layer.

Abstract: This specification discloses a magneto-optical recording medium in which on the opposite side of a second magnetic layer having a relatively low curie temperature and a relatively great coercive force, there are laminated a first magnetic layer and a third magnetic layer each having a relatively high curie temperature and a relatively small coercive force as compared with the second magnetic layer, the second magnetic layer has its curie temperature varying in the direction of film thickness thereof and has a curie temperature T.sub.L1 near the interface thereof with the first magnetic layer and has a curie temperature T.sub.L3 near the interface thereof with the third magnetic layer, and T.sub.L1 .noteq.T.sub.

Abstract: A method of making a magneto-optical disk. A first AlGeN dielectric film is formed by reactive sputtering on a substrate. Two targets, one of aluminum and one of germanium, are used in the sputtering in a mixed atmosphere having at least nitrogen gas. Alternatively, a single target using an aluminum germanium alloy can be used. A magnetic film is formed on top of this dielectric film. A second dielectric film is then formed on top of the magnetic film. An adhesive film is formed on top of the second dielectric film and a second substrate adhered thereto.

Abstract: An optical data storage medium is comprised of a data layer and a reference layer deposited onto a substrate. The data layer material is comprised of a transition metal rich rare earth-transition metal. The data layer has a destruction temperature greater than its Curie temperature. The reference layer is comprised of a transition metal poor rare earth-transition metal. The reference layer material has a Curie temperature greater than the destruction temperature of the data layer material. The result is a magneto-optic medium which may be recorded upon only once.

Abstract: An overwritable method of magnetooptical recording uses an over write capable magnetooptical recording medium that comprises a substrate and a magnetic layer. The magnetic layer is stacked on the substrate and includes first and second layers each having a perpendicular magnetic anisotropy. When a high-level laser beam irradiates the medium, the magnetization of the second layer is reversed and a bit of one magnetization direction is recorded in the first layer under the influence of the magnetization of the second layer. When a low-level laser beam irradiates the medium, a bit of opposite magnetization direction is recorded in the first layer under the influence of the second layer. This overwritable method of magnetooptical recording exhibits a high C/N ratio without decreasing recording sensitivity.

Abstract: A magneto-optical disc is fabricated by forming a first dielectric film, a recording film of a rare earth element-transition element alloy, and a second dielectric film on a transparent substrate in the described order and further forming an intermediate film between the recording film and the second dielectric film. The second dielectric film contains at least one metal element and nitrogen. By depositing Ti, Cr or Nb to form an intermediate film of 1-28 .ANG. thick, the disc is improved in magnetic field sensitivity and reliability. By depositing Co or Ni to form an intermediate film of 1-18 .ANG. thick, the disc is improved in magnetic field sensitivity and reproduction stability.

Abstract: A magneto-optical recording medium includes a magneto-optical layer, a reflection layer and an inorganic dielectric layer interposed therebetween. The dielectric layer is extremely thin so that it will exhibit almost no optical effect, thereby allowing a high CN ratio to be obtained. Thermal conductivity of the dielectric layer is so low that the magneto-optical and reflection layers are thermally isolated from each other. That is, if refractive index of the dielectric layer is n, thickness of the dielectric layer is T (nm), and the thermal conductivity of the dielectric layer is C (J (m sec K).sup.-1), then the thickness T is set within a range that satisfies the following equation:5n-4.ltoreq.T.ltoreq.(12n-4)(C/2.1).sup.-0.4where C.ltoreq.4J (m sec K).sup.-1.

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 first through fourth magnetic layers laminated in this order in such a way that an exchange coupling exists between any adjacent layers of the first through fourth magnetic layers so that a magnetization direction can be copied, wherein the first magnetic layer is a memory layer, the second magnetic layer is a writing layer, the third magnetic layer is a switching layer, and the fourth magnetic layer is an initializing layer. Further, respective Curie temperatures Tci satisfy an inequation Tc.sub.3 <Tc.sub.1 <Tc.sub.2, Tc.sub.4 (i=1, 2, 3, or 4 indicating an ordinal number of the magnetic layers); and the second magnetic layer exhibits an in-plane magnetization at room temperature, whereas, exhibits a perpendicular magnetization above a predetermined temperature set between the room temperature and Tc.sub.3 temperature.

Abstract: An optical data recording medium of the present invention includes: a substrate; a reflective material layer formed of light-reflective material, the reflective material layer being provided over the substrate; and an optical data recording layer for optically recording data therein and for optically reproducing the data therefrom, the optical data recording layer being formed over the reflective material layer. The reflective material layer is patterned so that the light-reflective material may be partly removed therefrom for selectively allowing a light beam irradiated on the substrate to pass therethrough to reach the optical data recording layer.

Abstract: A magnetooptic recording medium is composed of a transparent substrate, first and second magnetic layers and a reflecting layer. The first magnetic layer is formed on the transparent substrate and exhibits a large magneto-optical effect and has an axis of easy magnetization that is perpendicular to the film surface. The first magnetic layer is made of a Gd--Fe--Co amorphous alloy that is dominant in the iron group sublattice magnetization and the saturation magnetization lies within a range from 50 to 300 emu/cc. The second magnetic layer is formed on the first magnetic layer and has a larger coercive force at the room temperature than that of the first magnetic layer and a Curie temperature or a magnetic compensation temperature lower than that of the first magnetic layer and an axis of easy magnetization that is perpendicular to the film surface.

Abstract: A magneto-optical recording medium capable of overwriting by light modulation comprises a substrate, a first magnetic layer having a curie point T.sub.1 and a coercive force H.sub.1, a second magnetic layer having a curie point T.sub.2 and a coercive force H.sub.2, and a third magnetic layer having a curie point T.sub.3 and a coercive force H.sub.3. The first, second and third magnetic layers are successively laminated on the substrate. The first magnetic layer, the second magnetic layer and the third magnetic layer each are vertically magnetized film composed chiefly of an amorphous alloy of rare earth elements and transition metal elements, and satisfy the following conditions:H.sub.1 >H.sub.2 >H.sub.3,T.sub.1 >T.sub.2 and T.sub.3.By constituting the magneto-optical recording medium as above, the external magnetic field can be reduced to thereby prevent the disappearance of the recording bit and to enable the compactness of a recording apparatus to be accomplished.

Abstract: A magneto-optical recording medium on which rewriting is possible is composed of a substrate and a recording layer exhibiting perpendicular anisotropy formed thereon. The recording layer consists of at least a transition-metal layer and a rare-earth-metal layer, or at least two transition metal--rare earth metal alloy layers, which are alternately overlaid on each other, and each of the layers further contains a precious metal in an amount of 1 atom % to 10 atom %.

Abstract: An amorphous alloy containing uranium and a member selected from the group of N, P, As, Sb, Bi, S, Se, Te, Po and mixtures thereof; and use thereof for storage medium, light modulator or optical isolator.

Abstract: A read-only magneto-optical disk comprises at least a substrate and a magnetic layer built up thereon. The magnetic layer has a track with a second micro region .alpha..sub.1 (corresponding to a pit or mark) in which magnetization can be directed in a predetermined direction .uparw. under spot irradiation of a reproduction laser and a first micro region .alpha..sub.0 in which magnetization cannot be directed in the predetermined direction under the laser irradiation. Defining one of the micro regions as an information unit, information is expressed by presence or absence of the information unit, or by a length thereof. In a method and apparatus for reproducing from the disk, when the region .alpha..sub.1 is located within a heat-storing region a in the irradiation spot, the coercivity therein drops, and the magnetization is directed in the predetermined direction .uparw. under influence of an auxiliary magnetic field .uparw. (as if heat-visualized).

Abstract: A magnetic recording film and a magneto-optic recording system utilizing films. The film includes light and heavy rare earth elements and transition metal elements. The system can include dielectric layers and low magnetic coercivity layers in addition to the recording layer.

Abstract: A magneto-optical recording medium having a layered structure consisting of a first dielectric layer, magnetic recording layer, second dielectric layer and reflecting layer successively formed on a transparent substrate plate can be imparted with improved performance relative to the recording sensitivity and the C/N ratio when the recording layer and the second dielectric layer each have such a thickness that the angle .delta. given by the equation .delta.=tan.sup.-1 (.epsilon./.theta.k), in which .epsilon. is the Kerr ellipticity of the regenerative light and .theta.k is the Kerr rotation angle, does not exceed 10.degree., the thickness of the recording layer being in the range from 8 nm to 13.5 nm and the thickness of the second dielectric layer satisfying the relationship given by the inequality0.06.ltoreq.nd/.lambda..ltoreq.0.14,in which d is the thickness of the second dielectric layer, .lambda.

Abstract: In the magneto-optical recording medium with a transparent substrate, a film of dielectric indium oxide, tin oxide or metallic Ti is interposed between the substrate and the recording layer, to prevent deterioration of the properties thereof.

Abstract: An overwritable magneto-optical recording medium is disclosed. The recording medium comprises a first magnetic layer exhibiting vertical magnetic anisotropy and a second magnetic layer having a higher Curie temperature and a lower coercive force at room temperature in comparison with the first magnetic layer and exchange coupled with the first magnetic layer, wherein the second magnetic layer exhibits in-plane magnetic anisotropy and vertical magnetic anisotropy at room temperature and the vertical magnetic anisotropy relative to the in-plane magnetic anisotropy becomes larger in the vicinity of the Curie temperature of the first magnetic layer than at room temperature.Further, a recording method using the magneto-optical recording medium is also disclosed.

Abstract: A magneto optical disc is provided with: a substrate having a disc shape; and a ferrimagnetic layer formed on the substrate for recording information as a magnetization condition therein, the ferrimagnetic layer comprising material which Kerr rotation angle at a room temperature is substantially zero and which Kerr rotation angle at a predetermined reproducing temperature has a predetermined value other than zero, the predetermined reproducing temperature being higher than the room temperature and lower than a Curie point of the ferrimagnetic layer.

Abstract: A magneto-optical recording method for recording information in an overwrite mode in a magneto-optical recording medium by the application of a laser beam is disclosed. The magneto-optical recording medium includes a substrate, and at least two magnetic recording layers overlaid thereon, with an exchange force working at least between the two magnetic recording layers, and the Curie temperature of each of the two magnetic recording layers being substantially the same.

Abstract: A magneto optical disk comprising: a circular substrate; a recording layer, formed on the substrate, for magneto-optical recording of information; a readout layer, formed between the substrate and the recording layer, for the reproduction of information recorded on the recording layer, wherein the readout layer has a Curie temperature which is higher than the Curie temperature of the recording layer, and exhibits in-plane magnetization at room temperature and a change from in-plane magnetization to perpendicular magnetization when its temperature rises over a certain temperature as a result of the application of a light beam, and wherein the magnetic compensation temperature is set such that it increases from the peripheral edge of the magneto-optical disk toward the center thereof.

Abstract: A magnetooptical recording medium is provided with a transparent substrate, a first magnetic layer, a second magnetic layer having a higher Curie point and a lower coercive force than those of the first magnetic layer and being exchange coupled with the first magnetic layer. The medium further includes a third magnetic layer located between the first and second magnetic layers, so that the first magnetic layer is closer to the transparent substrate than the second and third magnetic layers and the third magnetic layer is closer to the transparent substrate than the second magnetic layer. Also disclosed is a process for recording on such a medium.

Abstract: A thin transparent epitaxial layer of a magnetizable material (e.g. gallium ferrite) is deposited on a substrate of a dielectric transparent material (e.g. gadolinium gallium garnet). A mask made from an oxidizable material (e.g. silicon) deposited on the epitaxial layer covers pixels defining rows and columns and exposes the other areas on the epitaxial layer. The epitaxial layer is then annealed at a suitable temperature (e.g. 500.degree. C.) for a suitable time (e.g. 10 minutes) to oxidize the silicon and reduce the Fe atoms in the pixel areas beneath the mask to Fe.sup.++ ions. This causes the pixel areas beneath the mask to be more easily magnetizable than the other areas in the epitaxial layer. The mask is then removed and a first insulating layer is deposited on the epitaxial layer. A first plurality of windings is then deposited on the first insulated layer in insulating relationship to one another.

Abstract: A magneto-optic memory and storage medium with the ability to directly write or overwrite ones and zeros at recording speed is described incorporating a radiant energy source, a control circuit for adjusting the power of the radiant energy beam and magneto-optic medium having a three layer sandwich comprising a magnetic bias layer, storage layer, and a switching layer therebetween functioning to switch from an antiferromagnetic state at low temperatures to a ferromagnetic state at temperatures above T.sub.AF. The invention overcomes the problem of direct overwrite of ones and zeros on magneto-optic media.

Abstract: The present invention pertains to a storage medium for use in a magneto-optical storage system. The storage medium comprises two layers of magnetic material, a storage layer and a read layer. The magnetic material of the storage layer has perpendicular (or vertical) axis of orientation; and within the storage layer the direction of magnetic orientation is either parallel or anti-parallel (up or down) relative to the direction of an impinging read radiation beam. In this storage system, the direction of orientation of magnetic material in one direction represents a first logical state, and a direction of orientation in the opposite direction represents a second logical state. The direction of orientation is thus a function of stored data.

Abstract: A magneto-optical memory element including: grooves, formed on at least one surface of a transparent substrate, for guiding a light beam; a magneto-optical recording layer formed on the surface of said transparent substrate on which the grooves are formed, wherein a width of each groove and a width of each land formed between the grooves are substantially equal, information is recorded on and reproduced from tracks on the grooves and the lands, and a groove depth d (track depth) is arranged such that 0.13.times..lambda./n.ltoreq.d.ltoreq. 0.18.times. .lambda./n, where .lambda. is a wavelength of the light beam and n is a refraction index of the transparent substrate. Assuming that a diameter of the light beam at a portion where a light intensity of the light beam becomes 1/e.sup.2 of a light intensity of the center of the light beam is L, a track pitch p is arranged such that 0.6.ltoreq.L/p.ltoreq.1.2. Therefore, even when the track density is increased, i.e.

Abstract: A method of reproducing information recorded on an optical recording medium includes the steps of directing a first reading optical beam and a second reading optical beam onto a recording portion on the optical recording medium to obtain a first electric output signal corresponding to the first beam interacting with the optical recording medium and a second electric output signal corresponding to the second beam interacting with the optical recording medium, and performing a non-linear operation and a linear-operation by using these first and second output signals, thereby obtaining an improved reproduced output signal.

Abstract: A magnetooptical disk has two axially space-apart translucent recording layers. Each translucent recording layer is axially closer to an outer surface of the disk than to the other recording layer. This geometry enables closely axially disposing a magnetic field biasing means to each of the recording layers from opposite axial sides of the disk, respectively. Laser beams are axially introduced into the disk to pass through one of the translucent recording layers in a defocussed state to reach a second recording layer in a focussed state. In this manner, recording in the second layer is effected by a modulated magnetic bias field using a constant intensity laser beam. Two sets of laser beams and magnetic biasing means are provided for recording on both data in both of the recording layers.

Abstract: A magneto-optical recording medium comprises a base film having a certain crystal plane oriented in parallel to a substrate and a recording film formed on the base film. The recording film is composed of plural pairs of Mn alloy group magnetic thin film layer having a C-axis-oriented crystalline magnetic anisotropy and a nonmagnetic thin film layer having an interatomic spacing approximate to that of the base film, alternately laminated each other, so that the Mn alloy group magnetic film having a C-axis-oriented crystalline magnetic anisotropy is epitaxially grown on the substrate at a low temperature through the base film with high thermal stability and great magneto-optical effect.

Abstract: A medium includes a readout layer, a memory layer, an adjusting layer for an exchange coupling force .sigma..sub.W, and a writing layer, and can perform an over-write operation upon radiation of a modulated laser beam. The readout layer essentially consists of GdFeCo, the memory layer essentially consists of TbFeCo, the adjusting layer essentially consists of GdFeCo, and the writing layer essentially consists of DyFeCo. The C/N ratio of the medium exceeds 53 dB. The C/N ratio is a value obtained when a plurality of mark.sup.H having a period of 1.6 .mu.m are written, and are read out so that medium noise is maximized as compared to other noise components.

Abstract: This invention is predicated upon applicants' discovery that conventional techniques for minimizing metal loss from sintered ceramic materials are not adequate in the fabrication of small ceramic components such as multilayer monolithic magnetic devices wherein a magnetic core is substantially surrounded by an insulating housing. Applicants have determined that this metal loss problem can be solved by providing the component with a housing layer having an appropriate concentration of metal. Specifically, if the insulating housing material around the magnetic core has, during the high temperature firing, the same partial pressure of metal as the magnetic core material, there is no net loss of metal from the core. In a preferred embodiment, loss of zinc from a MnZn ferrite core is compensated by providing a housing of NiZn ferrite or zinc aluminate with appropriate Zn concentrations. Similar considerations apply to other ceramic components.

Abstract: A magneto-optical playback method employing a magneto-optical recording medium having a playback magnetic layer, a recording magnetic layer, a transparent dielectric layer and a reflecting layer. The playback magnetic layer is so formed that its playback output R.times..theta..sub.k (in which R and .theta..sub.k represent the reflectivity and the Kerr rotation angle of the recording medium, respectively) is sufficiently small at any point lower than a threshold temperature T.sub.th at which the magnetization thereof is inverted. According to this method, a playback output is obtained by inverting the magnetization of merely the playback magnetic layer alone in a playback mode, thereby achieving ultrahigh-density recording with enhanced linear density (recording density on record tracks) and transverse-to-track density while improving the playback signal-to-noise ratio.

Abstract: An optomagnetic recording medium comprising a substrate plate and, provided thereon, a recording layer and a reflection layer, said reflection layer consisting of a thin layer of an alloy of aluminum and tantalum.

Abstract: Disclosed are medium and methods for storage and reading of stored information. The storage medium comprises an oxide layer having a plurality of pits and projections on the oxide layer surface. Information storage is achieved by applying voltage or light, in accordance to information signals, to the oxide layer, to differentially heat said oxide layer and create a plurality of portions which contain different quantities of oxygen. Stored information is read by the application of voltage or light to the oxide layer containing a plurality of portions containing different quantity of oxygen and detection of the electrical resistance or light reflectivity of each of said plurality of portions.

Abstract: Magneto-optical memory having a substrate of a material which is transparent for the visible-to-infrared spectral range, on which there are provided, in this sequence, a dielectric layer which is transparent for the visible-to-infrared spectral range and has a refractive index which is higher than the refractive index of the substrate and constitutes a diffusion barrier layer for oxygen and/or water, an in essence amorphous and/or in essence micro-crystalline magneto-optical layer with uniaxial anisotropy and a magnetic ordering temperature higher than ambient temperature and a top layer which acts as a reflection or interference layer and as a diffusion barrier layer for oxygen and/or water, the dielectric layer being a layer which is deposited from organic silicon materials by means of a PCVD process.

Abstract: In a photomagnetic eraser, information recorded on a magnetic-layer of a photomagnetic recording medium is erased or initialized by applying light over the photomagnetic recording medium from a light source in a reflector with heating and also by supplying a magnetic field to the photomagnetic recording medium along its axis of easy magnetization. In one form, a plurality of light sources may be disposed in the concave surface of a single reflector. Alternatively, the photomagnetic recording medium may be double-faced, and the light source and reflector may be disposed on each side of the double-face recording medium.

Abstract: This application concerns an optical storage with an optical storage medium having a plurality of storage fields arranged in matrix fashion, wherein each storage field of this storage field matrix comprises a storage position matrix consisting of a number of storage positions arranged in matrix fashion, and an X/Y deflection system for random-addressing a storage position of a storage field of the storage field matrix responsive to an X- and a Y-control signal generated by a control unit, so that a light beam impinging on the X/Y deflection system is directed to a storage position of a storage field of the optical storage medium corresponding to the position of the X/Y deflection system.

Abstract: A device for writing, reading or erasing a record carrier has a coil with a winding arranged between an objective lens and the record carrier. Optical radiation is focused to a spot, the converging beam passing through the coil opening. A core of a transparent material, having an index of refraction which significantly decreases vergence of the focused beam, is placed in the winding opening. As a result the diameter of the coil can be reduced, and permit increase of the generated magnetic field.

Abstract: An improved information-modulate magnetic field generating circuit for magneto-optical recording which uses a step-down transformer whose secondary winding has less turns than the primary winding, thus permitting substantial reduction of electric power for driving the magnetic head coil.

Abstract: A magneto-optic memory device, such as a magneto-optic disk or magneto-optic card having a pair of opposed substrates at least one of which is transparent. Between the substrates is a magneto-optic memory layer made of a stack of dielectric film, a rear earth-transition metal alloy thin film, a dielectric film and a light reflecting film built on the surface of the transparent substrate opposed to the other substrate. An adhesive layer covers the memory layer and bonds the transparent substrate to the other substrate. Lastly, a metal nitride film interposed between the light reflecting film of the memory layer and the adhesive layer.

Abstract: In an optical information recording medium comprising a substrate (11) of polycarbonate, a recording layer, and a reflecting layer (14) covering the reflecting layer and containing Al, an alloy layer (17) of a Ni-Cr alloy is deposited on the reflecting layer to sufficiently protect transmission of moisture into the reflecting layer. A covering layer (18) of ultraviolet curable resin may be deposited on the alloy layer. The recording layer is formed on the substrate and includes a magneto-optical layer (13) sandwiched between first and second interference layers (15, 16). For protecting transmission of moisture into the substrate, it is preferable that an additional layer (21) of SiO.sub.2 is deposited on the substrate opposite to the recording layer.

Abstract: An apparatus for applying a magnetic field has a permanent magnet, pivotally supported, which has an approximate cylindrical shape, respective semicircles of a circular section thereof being magnetized as N and S poles, and a driving coil, located in the vicinity of the permanent magnet so that the permanent magnet can partially penetrate inside the loops of the driving coil, the rotation and the positioning of the permanent magnet being controlled by the strength and/or directions of current flow in the driving coil. The apparatus is used for a magneto-optical disk storage. Since the driving coil is close to the permanent magnet, the pivoting of the permanent magnet can be controlled with a fast response. In addition, the apparatus can be made relatively small.

Abstract: A compact memory uses magnetic bubble technology for providing data storage. A three-dimensional arrangement, in the form of stacks of magnetic bubble layers, is used to achieve high volumetric storage density. Output tracks are used within each layer to allow data to be accessed uniquely and unambiguously. Storage can be achieved using either current access or field access magnetic bubble technology. Optical sensing via the Faraday effect is used to detect data. Optical sensing facilitates the accessing of data from within the three-dimensional package and lends itself to parallel operation for supporting high data rates and vector and parallel processing.

Abstract: A magneto-optical recording medium on which new information can be directly over-written over pre-existing recorded information. Such medium comprises two magneto-optical recording layers which have a difference in Curie temperature in the range of 0.degree. C. -25.degree. C. and which are separated from each other by a metal layer for the transfer of heat, such as aluminum. Recording is effected by scanning the medium with a write spot produced by a pulsed laser beam concurrently with application of an external magnetic field which is modulated in accordance with the information to be recorded. The layers may have equal Curie temperatures if they behave thermally asymmetrically. At any scanning position of the write spot the scanned superposed local areas of the two recording layers are heated thereby above the Curie temperature of at least one of such layers and then permitted to cool while being subjected to the external magnetic field.

Abstract: A magneto-optical recording medium is consisted of a recording layer, a readout layer and a writing layer. The readout layer is made of rare earth-transition metal alloys wherein an easy magnetization axis is parallel to the recording layer at room temperature, and the easy magnetization axis is perpendicular to the recording layer as the temperature of the readout layer is raised above a predetermined temperature by irradiating thereon with a light beam. The writing layer is made of rare earth-transition metal alloys having such coercive force that a magnetization direction thereof is switched by an external magnetic field at room temperature and Curie temperature that is above Curie temperature of the recording layer.

Abstract: Significant improvement in corrosion resistance of a magnetooptic material for electric and electronic applications is achieved by a composition (RE.sub.a, TM.sub.b)1-c-.sub.d M.sub.c Be.sub.d of specified content ratios of the components, typically a Tb-Fe-Co type alloy with combined addition of M and Be.

Abstract: A rewritable magneto-optical memory device for multi-wavelength recording and reproduction having a high packing density. The device is form by a plurality of magnetic film layers, each of which has a unique characteristic wavelength at which optical absorption and magneto-optical effect occur simultaneously, in which a selective writing on one of the plurality of magnetic film layers is realized by using a writing light beam incident on the plurality of magnetic film layers which has a wavelength equal to the characteristic wavelength of that one of the plurality of magnetic film layers, and a selective reading from that one of the plurality of magnetic film layers is realized by measuring Faraday rotation angle of a reading light beam incident on the plurality of magnetic film layers which has a wavelength equal to the characteristic wavelength of that one of the plurality of magnetic film layers.

Abstract: A magneto-optical recording medium having a first magnetic layer and a second magnetic layer having a higher curie point and a lower coercive force than those of the first magnetic layer, which magneto-optical recording medium satisfying a condition of ##EQU1## where H.sub.H is a coercive force of the first magnetic layer, H.sub.L is a coercive force of the second magnetic layer. M.sub.s is a saturation magnetization of the second magnetic layer, h is a film thickness of the second magnetic layer, and .sigma..sub.w is a magnetic wall energy between the first and second magnetic layers. The second magnetic layer contains an element which is not ferromagnetic at a room temperature. A magnetic field opposite in direction to the field of the first layer is applied to the second layer. A recording method is also present using such medium.

Abstract: An over write capable multi-layer magnetooptical recording medium comprises a substrate on which is stacked a magnetic layer structure including first and second magnetic layers having perpendicular magnetic anisotropy serving as a recording layer and as a reference layer, respectively. The first layer comprises an alloy composition given by the formula:(Tb.sub.U Dy.sub.100-U).sub.V (Fe.sub.100-W Co.sub.W).sub.100-VwhereinU=0 to 60 atomic %V=10 to 30 atomic %W=5 to 40 atomic %and the second layer satisfies the following condition: ##EQU1## wherein .sigma..sub.w : exchange coupling force,M.sub.S2 : saturation magnetization of second layerH.sub.C2 : coercivity of second layer, andt.sub.2 : film thickness of second layers.