Abstract: A magneto-optic disc recording system includes an E-shaped electromagnet for providing magnetic biasing selectively for the recording and erasing processes. The middle arm of the E comprises a first pole piece and is positioned radially with respect to the disc rotation, on the opposite side of the disc from, but aligned with, the path of radial motion of the focused recording/erasing light beam. The other arms of the E, parallel to the middle arm, comprise second pole pieces opposite in polarity from the first pole piece, and are positioned adjacent the disc recording surface on the opposite side of the disc from the middle arm. Two shoes of a magnetic material, coupled to the optical translation stage, provide a magnetic circuit between the respective second pole pieces and the area surrounding the objective lens focusing light on the disc recording surface, relaying a substantially vertical magnetic field through the disc at the point of incidence of the focused light beam.

Abstract: A magneto-optical recording medium is disclosed in which a magnetic thin film recording layer is formed by a magnetic material having a Curie temperature or magnetic compensation temperature as low as 50.degree. to 250.degree. C. and a coercive force as large as 1 KOe or more and having an easy axis of magnetization perpendicularly to the film surface. A substantially transparent magnetic material film layer of ferrite, garnet or the like is disposed adjacent the recording film layer, large in the Faraday rotation angle and having an easy axis of magnetization perpendicularly to the film surface. A transparent substrate is disposed on the side of incidence of light. The substantially transparent magnetic material layer of the ferrite, garnet or the like may increase the magneto-optical rotation angle in the magnetic thin film recording layer, or may increase the magneto-optical rotation angle by the Faraday effect.

Abstract: A magneto-optic disc recording system includes a cylindrical permanent magnet for providing magnetic biasing selectively for the recording and erasing processes. The magnet is positioned radially with respect to the disc rotation, on the opposite side of the disc from, but aligned with, the path of radial motion of the focused recording/erasing light beam. The poles of the magnet are diametrically opposed, and the magnet is axially rotatable. Circular eddy currents, induced by the magnetic field of the magnet on the surface of the rotating disc, generate a second magnetic field which opposes the field of the magnet, thus impelling rotation of the magnet. A stopping mechanism stops the rotation of the magnet with one or the other of its poles adjacent the disc, such that either a recording or erasing magnetic bias is selectively provided to the recording region.

Abstract: Disclosed is a new magnetic storage medium including a layer of amorphous material typically GdDyFe whose Curie recording point (e.g., 120.degree. C.) is lower than its crystallization point (e.g., 350.degree. C.) to enable crystallization to cause variations in its optical properties such as transmittance or reflectivity for thermomagnetic writing. Reversible recordings are set up on the amorphous material layer by a thermomagnetic writing technique, for example Curie point writing, while unchangeable or permanent recordings are set up on the amorphous material layer through laser-activated crystallization of the amorphous material layer.

Abstract: An optical head for a magneto-optical memory in which the major axis (the phase advance axis or phase lag axis) of optical anisotropy of a lens focusing a linearly polarized laser beam onto a magneto-optical recording medium is arranged to coincide with the direction of linear polarization of the laser beam incident upon the lens, thereby improving the extinction ratio.

Abstract: Amorphous alloys of two materials having antiferromagnetically-coupled magnetization sublattices, and capable of deposition as a thin film supporting small stable domains for thermo-magnetic recording. The thin-film material is an alloy of at least one rare-earth element and a transistion-metal element. A stable domain of a few microns diameter, allowing highest density of information recording, is achieved by providing the lowest possible wall energy to the domain, with a resulting low anisotropy.

Abstract: A method of recording information on a magneto-optic information storage medium having a normal magnetization film, comprising modulating a recording beam of light with the pieces of information to be recorded on the information storage medium; irradiating the normal magnetization film with the modulated beam of light in the presence of a bias magnetic field; detecting the sensitivity of recording of the information storage medium throughout the recording area of the information storage medium; and controlling the bias magnetic field to vary with the detected sensitivity of recording.

Abstract: A three-dimensional magnetic bubble memory apparatus formed of at least two arrays of sheets, with the sheets of each array being mounted in spaced and parallel relationship and with the sheets of the two arrays being perpendicular to one another, and with each sheet being formed of light-transparent material producing magnetic bubble domains, and with a multiplicity of bubble generators being located along one edge of each sheet and being responsive to selected input signals for producing arrays of magnetic bubbles for movement along parallel channels on each sheet to selected positions representative of binary data to be stored in the memory apparatus, and which includes a light source positioned on one side of each array for directing a polarized light beam to the corresponding array, and a multiplicity of photocells positioned on the other side of each array respectively aligned with the locations on the sheets of the corresponding array at which magnetic bubbles are selectively positioned so that the amp

Abstract: A light signal reading method in which a first light beam modulated to a polarized state in accordance with information magnetically recorded on a recording medium is caused to interfere with a second light beam of a frequency different from that of the first light beam, and the information being detected as a variation in the intensity of the interference light, and an apparatus therefor.

Abstract: A layer in a magnetic storage medium provides a biasing magnetic field for writing data. The layer exhibits a net magnetization with an orientation in a first direction when the layer is at a temperature below its compensation temperature and a net magnetization with an orientation in a second direction different from the first direction when heated as by a laser to a temperature above its compensation temperature, but below its Curie point temperature.

Abstract: A recording medium suitable for use in a photo-thermo-magnetic memory of high density recording, including a substrate; a first magnetic layer, such as an amorphous TbFe film, which has a large coercive force and whose axis of easy magnetization is oriented in the direction perpendicular to the surface of the first layer; and a second magnetic layer, such as an amorphous GdTbCoFe film, having (i) a larger polar Kerr rotation or reflection than that of the first layer, (ii) the same polarity of polar Kerr rotation as that of the first layer, (iii) a direction of its magnetic moment aligned in parallel with that of the first layer and (iv) a thickness permitting the transmittance of a light, such as laser beam, therethrough and being magnetically coupled with the first layer by an exchange interaction therebetween; the first and second magnetic layers being superimposed on the substrate in that order or in the inverse order.

Abstract: A region (21) having different magnetic energy from that of other portion is formed in a layer (1b) of soft magnetic material which has an easy axis of magnetization normal to the layer surface and is magnetized in one direction by applying an external bias magnetic field. By irradiating a light beam on the layer surface, a cylindrical magnetic domain b magnetized in the direction opposite to the magnetization direction is formed at a first stable position of the region (21). This cylindrical magnetic domain is moved to a second stable position by a second cylindrical magnetic domain c.multidot.b formed by the irradiation of light beam or by a temperature gradient whereby stable recording, reading thereof and accurate calculation function can be carried out.

Abstract: The novel optical recording medium, as in the prior art, has a transparent substrate bearing two recording layers, each addressable from only one side of the medium, but unlike prior 2-sided media, the two recording layers are on the same face of the substrate. When the novel medium is addressed from one side of the substrate, a thin-film barrier, such as an opaque metal, between the two recording layers prevents the more distant recording layer from responding to that energy. Preferably a tough, transparent cover layer is sealed to the substrate to protect the two recording layers.

Abstract: A magneto-optical recording medium comprising: a recording layer of a magnetic thin film low in the Curie temperature or magnetic compensation temperature and high in coersive force and having an easy axis of magnetization in a direction perpendicular to the film surface; a reproducing layer disposed adjacent the recording layer and large in the magnetic Kerr rotation angle and having an easy axis of magnetization in a direction perpendicular to the film surface; and a transparent substrate disposed on the side of incidence of light. In accordance with the present invention, a reflecting metal layer is provided for reflecting light having entered from the side of the transparent substrate and passed through the recording layer and the reproducing layer. A dielectric layer may be further disposed at least on one side of the transparent substrate or the reflecting metal layer with respect to the recording layer and the reproducing layer.

Abstract: A thermomagnetooptical memory device comprises a recording medium having a substrate on which there is a magnetooptically active layer. The magnetooptically active layer is present between a laser source and a layer reflecting radiation from the laser source. The device further includes lenses to focus radiation from the laser source onto selected locations on the recording medium, and magnetooptical detectors placed in the path of the radiation returning from the magnetooptically active layer. The magnetooptically active layer comprises a polycrystalline, oxidic material based on Fe.sup.3+ having a spinel structure and having a thickness chosen to cause destructive interference between the plane polarized radiation returning from the surface of the magnetooptic layer and plane polarized radiation returning from the reflecting layer and having passed through the magnetooptically active layer at least twice.

Abstract: A thermo-magnetic method for recording of a bit of information in each domain of an amorphous alloy thin-film layer supporting small stable domains. Each domain in the recording layer is first magnetized in a first direction, corresponding to a first binary state, by exposure to a saturation magnetic field. The remaining binary state is temporarily or permanently recorded in a particular domain by heating (to a lower or higher temperature) that domain volume of the recording layer above a predetermined temperature, but less than the melting temperature of the layer material, and thereafter cooling the heated domain in the presence of a bias magnetic field of direction opposite to, and magnitude less than, the saturation field. The binary state of each domain is read by interrogation with a beam of energy and utilization of differential effects between the interrogation beam and the direction of the magnetic field in the interrogated domain.

Abstract: A thermomagnetic recording method is capable of recording information on a layer of soft magnetic material which has an axis of easy magnetization normal to the surface of the layer and in which magnetic bubble domains are generated by application of a bias magnetic field. Information is recorded by radiating the layer with pulses of a focused beam so as to form a magnetic bubble domain having a magnetization opposite to a direction of the bias magnetic field. Recorded information is stable but can be easily erased.

Abstract: In a magnetic layer of a magnetooptical modulator having fixed magnetic single domain areas, the areas of the layer present between the single domain areas are made electrically conductive by reduction.

Abstract: A recording medium is provided which comprises (a) a first recording layer; (b) a second recording layer provided in contiguity to the first recording layer; and (c) a separation layer for spatially separating the first and second recording layer. The first recording layer has a sufficient film thickness not to permit the recording to be effected on the second recording layer, while the recording operation is performed on the first recording layer, and the recording operation is effected on the second recording layer at positions corresponding to defective portions in the first recording layer.

Abstract: An improved magneto-optical recording medium and a method of making the same, the medium including a substrate base and a magneto-optical recording layer formed on the base and composed of a plurality of layers each of which contains a rare earth metal and a transition metal. The relative concentration ratio between the rare earth metal and the transition metal in the layers varies cyclically in the direction of the thickness of the magneto-optical recording layer. The recording medium is conveniently manufactured by simultaneously depositing the transition metal and the rare earth metal by co-sputtering the two metals on a base and providing relative movement between the base and the metal sources during co-sputtering to produce the multilayer recording structure.

Abstract: An optical information storage system wherein information is read from a magneto-optical storage medium by indicating the storage medium with a first laser beam generated by a semiconductor laser and exploiting the self-coupling effect of the semiconductor laser in response to light reflected from the storage medium to generate a second laser beam. A Faraday rotator is disposed in an optical path along which the reflected light from the magneto-optical storage medium returns to the semiconductor laser and a polarization rotating angle of the Faraday rotator is selected so that the oscillating polarization plane of the semiconductor laser is changeable in dependence upon the perpendicular magnetization direction of the magneto-optical storage medium.

Abstract: A multi-layer magneto optical thin film recording medium is disclosed having very high carrier-to-noise ratios (at least 47 decibels) and high rotation angles. A transmission electron microscope photomicrograph (at 200,000 X) of one such medium is shown in FIG. 1. The magneto optic layer is a multi-phase amorphous material having magnetic anisotropy perpendicular to the plane of the thin film produced in a triode vacuum sputtering process at vacuums in the range of 4.times.10.sup.-3 to 6.times.10.sup.-4 Torr. Various transparent layers, such as dielectric intermediate and anti-reflective layers and a protective covering layer, are combined with the magneto optic layer and a reflective surface to yield media having enhanced carrier-to-noise ratio and magnetic optic angle of rotation.

Abstract: This specification discloses a magneto-optical information reading apparatus which comprises a device for causing a light beam polarized in a predetermined direction to enter a magnetic recording medium on which information is recorded, an analyzer provided in the optical path of the light beam modulated by the magneto-optic effect in accordance with the information, and a photodetector having the current amplifying function and photoelectrically detecting the light beam transmitted through the analyzer, and in which the following equation is substantially satisfied: ##EQU1## where .phi. is the transmission axis azimuth of the analyzer relative to the predetermined direction of polarization and .eta. is the extinction factor of the analyzer.

Abstract: Ferrimagnetic oxides of the following formula, ##EQU1## wherein Me represents at least one element selected from the group consisting of Ba, Sr and Pb, M.sub.I is at least one element selected from the group consisting of Ga and Al, M.sub.II is at least one element selected from the group consisting of Bi, Gd, Tb, Dy, Ho, La, Y, Co, Zn, Ti, Sc, In, Sn, Ca, Cr, Ni and Ge, 1.ltoreq.x.ltoreq.8, 0<y.ltoreq.6, 1.ltoreq.x+y.ltoreq.8, m is an ion valence of M.sub.I and n is an ion valence of M.sub.II, and a magneto-optical recording medium comprising a transparent substrate, a perpendicular magnetic-anisotropic magnetic film layer formed on the substrate, which magnetic film layer comprises one of the ferrimagnetic oxides of the above formula, and a reflection layer formed on the magnetic film layer, are disclosed.

Abstract: An optical reproducing system for reading out magnetically recorded data comprises an optical head (4,4a,4b,4c,4d) for copying magnetic pattern on a magnetic recording medium like a magnetic tape (1), a conversion system (5,6,7,8,9,10) for converting a magnetic pattern on the optical head (4 et al.) to an optical pattern by using the Faraday effect which rotates a polarization of an LED beam (light emission diode) or a laser beam according to magnetic polarity in a domain in said optical head, a charge coupled device (3, CCD) with a plurality of cells for converting beam energy polarized according to recorded data to correspond to electrical output signal. The CCD device effects the conversion or reading of a plurality of data simultaneously.

Abstract: A magneto-optical recording medium having an easy axis of magnetization in a direction perpendicular to the film surface, characterized in that a readout medium layer, a reflection layer and a recording medium layer are sequentially disposed in a direction of the incidence of a reading-out light, thereby to increase a reproduced output.

Abstract: A magneto-optic storage media which utilizes two layers or films of magnetic material, with the magneto-optic hysteresis loop of one of the films being of a sense opposite to the sense of the magneto-optic hysteresis loop of the other film. The media permits the Farraday effect polarization rotations produced by one of the magnetic films to be in phase with Kerr effect polarization rotations produced by the other of the magnetic films, such that additive mode conversion is provided from different portions of the media whereby the detected signal has an increased signal-to-noise ratio.

Abstract: A magnetic domain device has at least one post element formed from a material that exhibits magnetic domain characteristics and that is positioned on a nonmagnetic substrate material. A pair of electrical drive lines associated with a post element permit coincident current selection of the post element to nucleate a magnetic domain reversal, and an additional current introduced into an adjacent drive line establishes an additive magnetic field to assist the propagation of a domain wall associated with the nucleated magnetic domain reversal so that the direction of magnetization of the post element is reversed.

Abstract: A magneto-optical recording medium is disclosed, which comprises a transparent substrate, a vertical magnetic-anisotropic magnetic film layer formed thereon, which magnetic film layer comprises a ferrimagnetic oxide of the following formulaMeGa.sub.x Fe.sub.12-x O.sub.19wherein Me represents an element selected from the group consisting of Ba, Sr and Pb, and x is an integer of 3 to 8, and a reflection layer formed on the vertical magnetic-anisotropic film layer.

Abstract: There is disclosed a head assembly for use in a magneto-optic recording/playback system which includes a memory medium having a magnetic coating having a magnetic anisotropy in a vertical direction. A light beam is applied to the memory medium for recording and reproduction of information. The head assembly includes a polarizing prism and a Faraday effect element in an optical path for the light beam. There is needed only the single polarizer.

Abstract: Magneto-optic media and system optimization including a set of optimized magneto-optic media for use in a magneto-optic recording and readout system employing an incident readout light beam of a given fixed power, P.sub.o. The beam is delivered in a linearly polarized state to the magneto-optic media and the magneto-optic radiation received from the media is detectable by the system. Each member of the set of media comprises a reflective layer having a predetermined thickness, a first transparent layer overlying the reflecting layer and having a predetermined thickness and refractive index and a second light transmissive layer having a predetermined thickness and exhibiting absorptivity at the wavelength of said incident readout light beam and having magneto-optic conversivity and perpendicular anisotropy. Members of the set of optimized magneto-optic media may further included a third transparent layer overlaying the second transmissive layer and having a predetermined thickness and refractive index.

Abstract: A magneto-optic memory element consisting of a substrate provided with an amorphous layer of an alloy of a rare-earth metal and a transition metal. The layer has a uniaxial magnetic anisotropy. Such memory elements are suitable for storing digital information in the form of magnetized areas, the magnetizaiton direction of which can be read by means of the Kerr effect or Faraday effect. By adding bismuth to the alloy, the Kerr rotation and Faraday rotation can each be increased considerably, so that simpler reading of the stored information is possible.

Abstract: A magneto-optical memory element consisting of a substrate, provided with an amorphous layer of an alloy of a rare-earth metal and a transition metal. The layer has a uniaxial magnetic anisotropy. Such memory elements are suitable for storing digital information in the form of magnetized areas, the magnetization direction of which can be read by means of the Kerr effect or Faraday effect. By adding bismuth and/or tin to the alloy the Kerr rotation and Faraday rotation can each be increased considerably, so that simpler reading of the stored information is possible.

Abstract: Methods and apparatus for reversibly altering magnetic characteristics or domains of ferrimagnetic material by photomagnetic means, particularly by electron spin reversal (spin-flip). Photomagnetic electron spin reversal and inversion creating cylinder domains and their surrounding toroid domains of oppositely directed intrinsic magnetization in ferrimagnetic thin film material are achieved by means of signal modulated circularly polarized laser radiation. Three different stable conditions are detectable. The invention has particular application as a fundamentally new aproach to erasable digital data storage, providing means and methods for photomagnetically alterable and erasable data storage which can be detected by observing polarization of optical radiation directed through the ferrimagnetic material.

Abstract: A magneto-optic memory medium comprises a reflector exhibiting reflectance for light used for information reproduction and a magneto-optic magnetization film disposed on the reflector. When light is applied for information reproduction, the light impinges on the magnetization film and reaches the reflector. The light reflected through the reflector and the magnetization film is of use for information reproduction. In a preferred form of the magneto-optic memory medium, there is deposited on a transparent substrate a magnetic film having an axis of easy magnetization perpendicular to its surface. The magnetization film is overlaid with a reflective coating which is shaped into a strip configuration.

Abstract: This invention relates to an apparatus for detecting magneto-optical anisotropy which can be utilized as an information reproduction apparatus for detecting information recorded on a magnetic medium. The apparatus consists of a light source (10), a magneto-optically anisotropic medium (20), a polarization analyzer (33A) and a light detector (34). To avoid the information reproduction by means of the linearly polarized light as in the prior art, the apparatus of the present invention reproduces the information using the light source (10) which generates the elliptically polarized light. This makes it possible to reproduce the information having a high signal-to-noise ratio.

Abstract: A magnetic recording medium having a thin magnetic amorphous rare earth metal-transition metal alloy film is disclosed, the amorphous alloy film having an axis of easy magnetization in a direction substantially vertical to the film surface and containing a crystalline phase in the amorphous phase. The magnetic recording medium exhibits high coercive force over a wide compositional range.

Abstract: A small, highly reliable and inexpensive switching equipment, in which digital signals to be switched, stored as the presence or absence of magnetic domains in a first magnetic sheet or applied as the presence or absence of light to a flat plane formed by bundles of optical fibers, are switched by switching condition determining signals stored as the presence or absence of magnetic domains in a second magnetic sheet.

Abstract: A storage medium for use in a device for thermomagnetically writing and magneto-optically reading information. The medium comprises a nonmagnetizable substrate bearing an amorphous layer of a rare earth metal-iron type alloy (which contains from 20 to 30 atomic percent rare-earth metal/iron and 70 to 80 atomic percent iron) to which 15 to 30 atomic percent boron is added. The amorphous layer has a perpendicular easy axis of easy magnetization, required for the writing process, with a good stability against crystallization when heated to higher temperatures.

Abstract: A display system using the dispersive Faraday coefficient of a magnetic screen to obtain a color display from white light is disclosed. A beam of energy is directed upon a magnetic screen while concurrently an intensity modulated magnetic field is directed normal to the surface of the magnetic screen. The combination of the heating effect of the energy beam and the magnetic orienting effect of the intensity modulated magnetic field established localized areas of differing magnetic characteristics over the planar surface of the magnetic screen. Subsequently, a polarized beam of white light that floods the magnetic screen is, for each of several wave lengths, differently rotated upon passing through each of the areas of differing magnetic characteristics in the magnetic screen. The beamlets that are formed by the so-differently rotated areas of the polarized white light beam are then passed through an uncrossed analyzer, which beamlets appear as a multicolored projection upon the magnetic screen.

Abstract: Wave propagation in thin film optical waveguides using gyrotropic or anisotropic material in either the substrate or adjacent top layer with respect to the thin film waveguide is analyzed and a mode converter capable of converting TE to TM or TM to TE polarization is disclosed. Several mode converters constructed in accordance with the present invention are set forth. Also disclosed are other optical circuit elements constructed from such mode converters including a gyrator, isolator, an optical switch, and a non-destructive optical readout for magnetic memories.

Abstract: The invention relates to a device for magneto-optic memories controlled by light and/or heat in an external magnetic field, in which the magneto-optic material of the memory has a photoconductive layer which can be activated by the control beam and which can be controlled by means of electrodes provided thereon via a current or voltage source.

Abstract: A holographic optical memory utilizes an optical heterodyne technique to significantly increase the signal-to-noise ratio during the readout stage of operation. A light source provides a coherent light beam which is split into a readout beam and a local oscillator beam. The readout beam is directed to one of the holograms stored in the memory medium and a portion of the readout beam is diffracted by the hologram to form a reconstructed image of the bit pattern stored in the hologram at the reconstructed image plane. The local oscillator beam is superimposed with the diffracted portion of the readout beam. An optical frequency translator is positioned in either the readout beam or the local oscillator beam to cause the beams to have different optical frequencies. Therefore, when the two beams are superimposed, a beat frequency signal is produced. An array of detectors is positioned at the reconstructed image plane to receive the superimposed beams.