Magneto-optical Patents (Class 365/122)
  • Patent number: 8379470
    Abstract: A semiconductor memory system includes a controller and a memory device that are optical-interconnected. The controller includes a control logic configured to generate a control signal for controlling the memory device and a transmitter configured to convert the control signal into an optical signal, and output the optical signal. The memory device includes a receiving unit filter configured to convert the optical signal into an electric signal, and the electric signal based on a supply voltage corresponding to a period of the optical signal or the electric signal.
    Type: Grant
    Filed: August 12, 2010
    Date of Patent: February 19, 2013
    Assignee: Samsung Electronics Co., Ltd.
    Inventors: Sung-dong Suh, Kyoung-ho Ha, Seong-gu Kim, Soo-haeng Cho, In-sung Joe
  • Patent number: 8270198
    Abstract: A nonvolatile optical memory element in which a ferromagnetic body is provided on a semiconductor causes such a problem that in a case where magnetization of the ferromagnetic body is read by light, magneto-optical response becomes very small when the ferromagnetic body is small in volume. The present invention provides a memory element, a memory device, and a data reading method, each of which is applicable to data reading from a nonvolatile optical memory element. In a nonvolatile optical memory element having a structure in which a ferromagnetic body is provided on a semiconductor that is connected to an optical waveguide, electrons are injected into the semiconductor via the ferromagnetic body so that the electrons that are spin-polarized according to a magnetization direction of the ferromagnetic body are injected into the semiconductor, thereby enlarging a region in which a photomagnetic effect occurs effectively.
    Type: Grant
    Filed: July 27, 2010
    Date of Patent: September 18, 2012
    Assignee: National Institute of Advanced Industrial Science and Technology
    Inventors: Vadym Zayets, Koji Ando, Shinji Yuasa, Hidekazu Saito
  • Patent number: 8154957
    Abstract: A magneto-optical device (MOD) with optically induced magnetization for use in magnetic field sensors as a magnetic element pinning a magnetization in a preferred direction of a ferromagnetic layer as well as a magnetic memory cell for magneto-optical recording. The MOD comprises the Mg—Mg—Co ferrite film deposited on a magnesium oxide (MgO) substrate. The ferrite film is illuminated at room temperature with a circularly polarized light (CPL) in a static magnetic H-field (about of 3 kOe) normal to the illuminated ferrite film surface. At certain (“writing”) combinations of H, sigma (CPL helicity), the long-lived optically induced magnetization with a unidirectional anisotropy, stable to a conventional demagnetization occurs. For readout of information, conventional magnetoresistive sensors and MFM can be used. To erase information, the ferrite film should be illuminated with two field-light combinations, other than “writing”, or annealed at temperature higher than 530 degrees C.
    Type: Grant
    Filed: May 24, 2011
    Date of Patent: April 10, 2012
    Inventors: Esfir Z. Katsnelson, Mark M. Chervinsky
  • Patent number: 8040712
    Abstract: An information memory device using an electromagnetic-wave resonance phenomenon is provided to achieve both high density and long-period storage of stored data. Memory cells are three-dimensionally arranged in the inside of a solid-like medium which is not contacted with a surface of the medium, and the memory cell has resonance characteristics to electromagnetic waves depending on the space coordinates of the memory cell. For the medium, a material is selected so that an electromagnetic wave having the resonance frequency of the memory cell. By observing absorption spectra of the irradiated electromagnetic wave or emission spectra after the absorption, three-dimensional space coordinates of the memory cell are calculated.
    Type: Grant
    Filed: December 17, 2008
    Date of Patent: October 18, 2011
    Assignee: Hitachi, Ltd.
    Inventors: Takao Watanabe, Toshimichi Shintani, Takeshi Maeda, Akemi Hirotsune, Yoshitaka Bito
  • Publication number: 20110026296
    Abstract: A nonvolatile optical memory element in which a ferromagnetic body is provided on a semiconductor causes such a problem that in a case where magnetization of the ferromagnetic body is read by light, magneto-optical response becomes very small when the ferromagnetic body is small in volume. The present invention provides a memory element, a memory device, and a data reading method, each of which is applicable to data reading from a nonvolatile optical memory element. In a nonvolatile optical memory element having a structure in which a ferromagnetic body is provided on a semiconductor that is connected to an optical waveguide, electrons are injected into the semiconductor via the ferromagnetic body so that the electrons that are spin-polarized according to a magnetization direction of the ferromagnetic body are injected into the semiconductor, thereby enlarging a region in which a photomagnetic effect occurs effectively.
    Type: Application
    Filed: July 27, 2010
    Publication date: February 3, 2011
    Applicant: National Institute of Advanced Industrial Science and Technology
    Inventors: Vadym Zayets, Koji Ando, Shinji Yuasa, Hidekazu Saito
  • Patent number: 6912148
    Abstract: A system for writing data to and reading data from a magnetic semiconductor memory utilizing a spin polarized electron beam. The magnetic semiconductor memory comprises a plurality of storage locations, each storage location includes a magnetic material and a layer of semiconductor material capable of emitting photons. The method of reading data from the magnetic semiconductor memory comprising steps of directing a spin-polarized electron beam at the magnetic semiconductor memory, and detecting the light emission state of the semiconductor layer from the magnetic semiconductor memory.
    Type: Grant
    Filed: July 21, 2003
    Date of Patent: June 28, 2005
    Assignee: Intel Corporation
    Inventors: Eric C. Hannah, Michael A. Brown
  • Publication number: 20040042245
    Abstract: A fail repair circuit of a nonvolatile ferroelectric memory device and a method for repairing the same are disclosed, in which a redundancy time can be reduced and a redundancy algorithm can be changed or added at any time.
    Type: Application
    Filed: September 3, 2003
    Publication date: March 4, 2004
    Applicant: HYNIX SEMICONDUCTOR INC.
    Inventors: Hee Bok Kang, Hun Woo Kye, Duck Ju Kim, Je Hoon Park
  • Patent number: 6649285
    Abstract: A magneto-optical recording medium includes a magnetic reproducing layer having an axis of easy magnetization in a direction perpendicular to its layer surface, a magnetic intermediate layer formed on the magnetic reproducing layer and having an axis of easy magnetization in a plane at a room temperature, and a magnetic recording layer formed on the magnetic intermediate layer and having an axis of easy magnetization in a direction perpendicular to its layer surface. The magnetic reproducing layer has a composition of GdxFeCoy where 22 at %≦x≦25 at % and 16 at %≦y≦23 at %.
    Type: Grant
    Filed: December 20, 2000
    Date of Patent: November 18, 2003
    Assignee: Fujitsu Limited
    Inventor: Tetsuo Hosokawa
  • Patent number: 6567331
    Abstract: A reverse bias voltage in combination with selective illumination can selectively write data into optical memory. The writing process can be completed quickly since parallel writing of data may be performed. The writing process generates an avalanche current that is used to change an element. The change can be destruction of the element or may be the alteration of property such as conductance or work function.
    Type: Grant
    Filed: June 18, 2001
    Date of Patent: May 20, 2003
    Assignee: Velor Incorporated
    Inventors: Boris Chernobrod, Vladimir Schwartz
  • Patent number: 6455174
    Abstract: A magnetic recording medium comprises, on a substrate, a recording auxiliary layer, a recording holding layer, recording control layer, and a recording layer. The recording layer is constructed by using a ferri-magnetic material having perpendicular magnetization. The data can be recorded at a super high density by using the recording and reproducing head of the present invention, because the recording layer has the perpendicular magnetization. The disappearance of data, which would be otherwise caused by the thermomagnetic relaxation phenomenon, is suppressed after recording the data, because the recording layer has large coercive force at the room temperature. The data, which is recorded at the super high density on the magnetic recording medium, can be reproduced by using a magnetic resistance element carried on the recording and reproducing head.
    Type: Grant
    Filed: November 3, 1999
    Date of Patent: September 24, 2002
    Assignee: Hitachi Maxell, Ltd.
    Inventors: Hiroki Takao, Yuji Yamazaki, Susumu Imai, Hiroyuki Awano, Katsusuke Shimazaki
  • Patent number: 6436524
    Abstract: When recording using magnetic field modulation recording, the magneto-optical recording medium which is disclosed is capable of satisfactory recording with a low magnetic field. This recording medium is a layered superposition of a recording layer 13 and an auxiliary recording layer 14 having a film thickness of less than or equal to 100 angstroms. The recording layer 13 is a film having an easy perpendicular axis of magnetization whose value of magnetization at room temperature is at least 150 emu/cc, and for example a heavy rare earth—transition metal alloy, a magnetic multilayer film which employs a precious metal, an oxide like a garnet or Spinel ferrite, or some other magnetic alloy may be used. The auxiliary recording layer 14 is typically a heavy rare earth—transition metal alloy, and has a Curie temperature higher (desirably at least 30K higher) than that of the recording layer 13.
    Type: Grant
    Filed: January 13, 1998
    Date of Patent: August 20, 2002
    Assignee: Seiko Epson Corporation
    Inventors: Masaya Ishida, Takeo Kawase
  • Patent number: 6403148
    Abstract: A magnetooptical recording medium includes a first magnetic layer, a second magnetic layer whose Curie temperature is lower than that of the first magnetic laye, and a third magnetic layer, comprising a vertically-magnetizing film, whose Curie temperature is higher than that of the second magnetic layer. The first magnetic layer, the second magnetic layer and the third magnetic layer are in a state of exchange coupling with each other at a portion of a vertically-magnetizing film. A domain walls formed in the first magnetic layer moves when the temperature of the medium has been raised to at least the Curie temperature of the second magnetic layer.
    Type: Grant
    Filed: December 23, 1999
    Date of Patent: June 11, 2002
    Assignee: Canon Kabushiki Kaisha
    Inventors: Tsutomu Shiratori, Tomoyuki Hiroki
  • Patent number: 6261707
    Abstract: A magneto-optical recording medium is composed of a base which has a property that a light can be transmitted therethrough, a readout layer formed on the base, which has in-plane magnetization at room temperature, whereas, a transition occurs from in-plane magnetization to perpendicular magnetization as the temperature thereof is raised and a recording layer formed on the readout layer for recording information magneto-optically. A recording and reproducing method and the optical head are designed for the magneto-optical recording medium. By the recording and reproducing method using the optical head, information recorded at high density can be reproduced.
    Type: Grant
    Filed: November 3, 1993
    Date of Patent: July 17, 2001
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Yoshiteru Murakami, Junji Hirokane, Junichiro Nakayama, Junsaku Nakajima, Akira Takahashi, Kenji Ohta, Naoyasu Iketani
  • Patent number: 6153318
    Abstract: A composition of materials that is ferromagnetic and whose properties may be varied by means of an applied electric field and has at least a first and second layer. The first layer may be a substance of the formula III-V, wherein III is at least one element of Group IIIA, and V is at least one of the elements As and Sb and may include other elements of Group VA. The second layer may be a substance of the formula Mn-V, wherein V is at least one of the elements As and Sb present in the first layer. This second layer may be less than approximately 500 nm thick, but thick enough to be ferromagnetic. The first layer and said second layer may be crystalline.
    Type: Grant
    Filed: April 30, 1997
    Date of Patent: November 28, 2000
    Inventor: Gerald M. Rothberg
  • Patent number: 6139980
    Abstract: An information recording medium and a reading method thereof for realizing high density recording and recording/reading a direction of magnetization at minute bit length and bit width, which comprises a substrate having a first magnetic layer which is capable of thermo-magnetically recording and a second magnetic layer which is capable of being exchange coupled with the first magnetic layer formed thereon in this order, is performed by detecting a direction of magnetization transferred onto the second magnetic layer from variations in magnetic flux while emitting a light beam thereon.
    Type: Grant
    Filed: November 10, 1997
    Date of Patent: October 31, 2000
    Assignee: Fujitsu Limited
    Inventor: Koji Matsumoto
  • Patent number: 6139949
    Abstract: A magneto-optical recording medium in which information can be overwritten by a magnetic field modulation method, is provided with a magnetic thin film satisfying an inequality t.times.M.sub.s <5 .mu.m.multidot.emu/cc wherein the film thickness is, represented by t .mu.m and the saturating magnetization is represented by M.sub.s emu/cc. Even in the case where the intensity of the modulated magnetic field applied to the magneto-optical recording medium is small, a carrier to noise ratio C/N of not. less than a predetermined value and a jitter of not more than a predetermined value can be realized.
    Type: Grant
    Filed: April 22, 1993
    Date of Patent: October 31, 2000
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Kazuhiko Tsutsumi, Tatsuya Fukami
  • Patent number: 6096444
    Abstract: A magneto-optical recording medium of a three-layered structure (consisting of a readout layer, an intermediate layer, and a recording layer), capable of double-mask magnetically-induced super-resolution readout, has magnetic properties such that the exchange coupled force between the readout layer (a GdFeCo film) and the intermediate layer (a GdFe film) decrease with increasing temperature, while the exchange coupled force between the intermediate layer and the recording layer (a TbFeCo film) increase with increasing temperature. The magnetic property of the readout layer is transition-metal magnetization dominant, and that of the intermediate layer is rare-earth magnetization dominant.
    Type: Grant
    Filed: February 2, 1998
    Date of Patent: August 1, 2000
    Assignee: Fujitsu Limited
    Inventors: Ken Tamanoi, Koji Matsumoto, Keiji Shono
  • Patent number: 6077585
    Abstract: An optical recording medium having at least one aluminum nitride and silicon nitride composite dielectric layer is provided. The amount of aluminum nitride in the dielectric layer, x, is more than zero and less than or equal to about 95 mol %. The amount of silicon nitride in the layer is represented as (100-x) and is equal to or greater than about 5 and less than 100 mol %. The refractive index of the composite dielectric layer is between about 1.70 and 2.15. The composite dielectric layer is sandwiched between a transparent support such as a plastic transparent support and an optical recording layer adapted to be irradiated by laser light in order to read, write or erase information in order to protect the recording layer.
    Type: Grant
    Filed: March 19, 1992
    Date of Patent: June 20, 2000
    Assignee: Seiko Epson Corporation
    Inventor: Akira Aoyama
  • Patent number: 6027825
    Abstract: A magnetooptical recording medium includes a first magnetic layer, a second magnetic layer whose Curie temperature is lower than that of the first magnetic layer, and a third magnetic layer, comprising a vertically-magnetizing film, whose Curie temperature is higher than that of the second magnetic layer. The first magnetic layer, the second magnetic layer and the third magnetic layer are in a state of exchange coupling with each other at a portion of a vertically-magnetizing film. A domain walls formed in the first magnetic layer moves when the temperature of the medium has been raised to at least the Curie temperature of the second magnetic layer.
    Type: Grant
    Filed: June 5, 1997
    Date of Patent: February 22, 2000
    Assignee: Canon Kabushiki Kaisha
    Inventors: Tsutomu Shiratori, Tomoyuki Hiroki
  • Patent number: 6020079
    Abstract: A magneto-optical recording medium capable of performing magnetically induced super resolution reproduction by perfectly masking a mark adjacent to a mark to be reproduced. The magneto-optical recording medium includes a transparent substrate, a magnetic reproducing layer laminated on the transparent substrate, a magnetic control layer laminated on the reproducing layer, and a magnetic recording layer laminated on the control layer. The reproducing layer has an easy axis of magnetization in a plane at room temperature. Each of the control layer and the recording layer has an easy axis of magnetization perpendicular to the substrate.
    Type: Grant
    Filed: February 25, 1998
    Date of Patent: February 1, 2000
    Assignee: Fujitsu Limited
    Inventors: Koji Matsumoto, Keiji Shono
  • Patent number: 6001467
    Abstract: A magneto-optic memory medium comprising a dielectric film, a magneto-optic memory film, a dielectric film and a reflective film superposed in layers on a light trnasmitting substrate, the magneto-optic memory film being a rare earth-transition metal alloy film having the composition formula of:(Gd.sub.x Tb.sub.1-x).sub.y Fe.sub.1-ywherein x is 0.58 to 0.62, and y is 0.27 to 0.33, which is useful as a magneto-optic disc or magneto-optic card.
    Type: Grant
    Filed: February 5, 1993
    Date of Patent: December 14, 1999
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Kenji Ohta, Akira Takahashi, Yoshiteru Murakami, Junichiro Nakayama, Tomoyuki Miyake
  • Patent number: 5958575
    Abstract: A magneto-optical recording medium is disclosed in which magnetic layer has a multi-layer structure consisting of an artificial lattice film constituted by a Co layer and a Pt layer and/or a Pd layer stacked together and a rare earth-transition metal layer. High coercivity may be achieved by the rare earth-transition metal film whilst a satisfactory Kerr rotation angle in the short wavelength range may be assured by the artificial lattice film. The magneto-optical recording medium may cope with the next-generation high density recording employing a short wavelength laser.
    Type: Grant
    Filed: October 26, 1995
    Date of Patent: September 28, 1999
    Assignee: Sony Corporation
    Inventors: Kensuke Fijimoto, Shunichi Hashimoto, Yoshitaka Ochiai
  • Patent number: 5955191
    Abstract: A super-resolution magneto-optical recording medium has a reproducing layer, an in-plane magnetization layer and a recording layer. The reproducing layer and the recording layer are magnetostatically coupled, and each of the layers is made of a rare-earth transition-metal alloy which has a greater transition-metal sublattice moment than the compensation composition, and exhibits perpendicular magnetization, if it exists alone. At a temperature not more than the Curie temperature, the in-plane magnetization layer is exchange-coupled with the reproducing layer so as to allow the reproducing layer to exhibit in-plane magnetization. Since the reproducing layer is allowed to exhibit in-plane magnetization by the in-plane magnetization layer, it is not necessary to use a material containing a greater rare-earth metal sublattice moment as the reproducing layer.
    Type: Grant
    Filed: July 22, 1997
    Date of Patent: September 21, 1999
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Junji Hirokane, Yoshiteru Murakami, Akira Takahashi
  • Patent number: 5940314
    Abstract: A ultra-high density memory device utilizing a photoinductive ferromagnetic thin film. A photoinductive ferromagnetic thin film is formed on a GaAs substrate, and a tip is arranged so as to face the photoinductive ferromagnetic thin film. The GaAs substrate is disposed on an xyz scanner, and the three-dimensional positional relationship between the GaAs substrate and the tip is changed by the xyz scanner. Blue light is radiated onto the thin film in order to make the magnetization orientation of molecules uniform. Through application of a relatively high voltage, a relatively large current is caused to flow between the tip and the substrate, so that randomization of the magnetization orientation of molecules of the photoinductive ferromagnetic thin film; i.e., writing operation is carried out.
    Type: Grant
    Filed: January 20, 1998
    Date of Patent: August 17, 1999
    Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho
    Inventors: Motofumi Suzuki, Takeshi Ohwaki, Yasunori Taga, Hiroshi Tadano, Testu Kachi, Yuichi Tanaka, Kazuyoshi Tomita
  • Patent number: 5922177
    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.
    Type: Grant
    Filed: July 9, 1998
    Date of Patent: July 13, 1999
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Naoyasu Iketani, Yoshiteru Murakami, Akira Takahashi, Kenji Ohta
  • Patent number: 5821004
    Abstract: A magneto-optical recording medium having a recording layer which has a first magnetic film, a second magnetic film and a third magnetic film in this order from a laser beam incident side, in which the second magnetic film has a perpendicular anisotropy in a temperature range from room temperature to a Curie temperature, the first magnetic film has an in-plane anisotropy when there is no temperature increase by the irradiation of a laser beam or a perpendicular anisotropy when the temperature is raised by the irradiation of the laser beam, and an exchange coupled force is present between the first magnetic film and the second magnetic film.
    Type: Grant
    Filed: November 30, 1992
    Date of Patent: October 13, 1998
    Assignee: Matsushita Electric Industrial Co., Ltd
    Inventors: Yasumori Hino, Yoshihiko Kudoh, Masahiro Birukawa, Norio Miyatake
  • Patent number: 5814400
    Abstract: A magneto-optical recording medium comprises in combination: a magneto-optical recording layer capable of writing or erasing information by a laser beam and an external magnetic field and of reading the information by a Kerr effect; and a substrate having the magneto-optical recording layer formed thereon. The magneto-optical recording layer has at least two layers, including a first magneto-optical recording layer and a second magneto-optical recording layer which are magnetically coupled together. The first magneto-optical recording layer is a layer providing a greater magneto-optical effect in a short light wavelength range than the second magneto-optical recording layer though that having less perpendicular magnetic energy than this, as is provided on an irradiation side of the laser beam. It provides advantages in both the magneto-optical effect and perpendicular anisotropy in consideration of the thicknesses or compositions of the first and second magneto-optical recording layers.
    Type: Grant
    Filed: May 20, 1991
    Date of Patent: September 29, 1998
    Assignees: Hitachi, Ltd., Hitachi Maxell, Ltd.
    Inventors: Fumiyoshi Kirino, Yoshinori Miyamura, Junko Nakamura, Norio Ohta, Masahiko Takahashi, Ryo Suzuki
  • Patent number: 5814418
    Abstract: In one embodiment, the magneto-optical recording medium of the present invention has a recording layer structure including at least a readout magnetic film, a control magnetic film, and a recording magnetic film. The readout magnetic film is a perpendicular magneto-anisotropy film at a temperature in a predetermined range. The control magnetic film provided between the readout magnetic film and the recording magnetic film has a prescribed structure so as to assume a perpendicular magneto-anisotropy film at a temperature in a predetermined range and an in-plane magneto-anisotropy film at a temperature in a range other than the predetermined range.
    Type: Grant
    Filed: September 26, 1995
    Date of Patent: September 29, 1998
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Keiji Nishikiori, Yasumori Hino, Masahiro Birukawa
  • Patent number: 5726964
    Abstract: Scanning head including a magneto-optical element and scanning device including the scanning head. A scanning head having a head face (1) comprises flux-guiding elements (3a, 3b) and a magneto-optical element (5). The magneto-optical element is disposed in a gap plane (4) which extends between flux-guiding elements.
    Type: Grant
    Filed: July 13, 1995
    Date of Patent: March 10, 1998
    Assignee: U.S. Philips Corporation
    Inventors: Hans W. Van Kesteren, Jacobus J. M. Ruigrok
  • Patent number: 5723227
    Abstract: A magneto-optical recording medium capable of performing magnetically induced super resolution reproduction by perfectly masking a mark adjacent to a mark to be reproduced. The magneto-optical recording medium includes a transparent substrate, a magnetic reproducing layer laminated on the transparent substrate, a magnetic control layer laminated on the reproducing layer, and a magnetic recording layer laminated on the control layer. The reproducing layer has an easy axis of magnetization in a plane at room temperature. Each of the control layer and the recording layer has an easy axis of magnetization perpendicular to the substrate.
    Type: Grant
    Filed: January 4, 1995
    Date of Patent: March 3, 1998
    Assignee: Fujitsu Limited
    Inventors: Koji Matsumoto, Keiji Shono
  • Patent number: 5706259
    Abstract: In a magneto-optical recording medium for super resolution reproduction, a recording layer having a Curie temperature of 300.degree. C. or higher is used. An inhibition force for inhibiting movement of a domain wall in the recording layer is enhanced, while the magnetization is sufficiently increased such that a contraction force, which decreases a surface area of the domain wall, can be decreased. Thus, recording domains become stable during recording and erasing. Further, cross erasing characteristics can be improved, while maintaining previously used recording and erasing powers. The inhibition force becomes larger than the contraction force, even if the Curie temperature is low, when the recording layer is made of a first magnetic material for forming recording domains which have a compensation temperature between 0.degree. and 200.degree. C., or when the compensation temperature of the recording layer is between 0.degree. and 200.degree. C.
    Type: Grant
    Filed: May 18, 1995
    Date of Patent: January 6, 1998
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Yuichi Fukamachi, Masahiro Birukawa
  • Patent number: 5700567
    Abstract: In a magneto-optical recording medium comprising a first dielectric layer, a recording layer, a second dielectric layer, and a metal reflective layer stacked on a substrate, the second dielectric layer is formed of a mixture of a rare earth element oxide, silicon oxide, and silicon nitride. The medium has increased recording sensitivity and provides stable recording/reproducing performance with low error rate and high resolution.
    Type: Grant
    Filed: November 16, 1995
    Date of Patent: December 23, 1997
    Assignee: TDK Corporation
    Inventor: Hajime Utsunomiya
  • Patent number: 5681633
    Abstract: A magneto optical disc, is provided with: a record layer to which information is recorded in a perpendicular magnetization condition; a switch layer, which perpendicular magnetic anisotropy is reduced at a room temperature and is increased at a temperature close to a predetermined reproduction temperature; and a reproduction layer opposed to the record layer through the switch layer to have a switched connection with the record layer by the switch layer.
    Type: Grant
    Filed: May 6, 1996
    Date of Patent: October 28, 1997
    Assignee: Pioneer Electronic Corporation
    Inventors: Nobuaki Onagi, Nobuyasu Negishi, Takamasa Yoshikawa
  • Patent number: 5679474
    Abstract: A magneto-optical recording medium with wide operating margins is disclosed.The magneto-optical recording medium includes a vertical magnetic films of exchange-coupled liminated structure composed of a first magnetic layer with a high coercive force H.sub.H and a low Curie temperature T.sub.L and a second magnetic layer with a lower coercive force H.sub.L and a higher Curie temperature T.sub.H in comparison with those of the first magnetic layer. The first magnetic layer has a gradient of the Curie temperature along the direction of thickness of the layer so that the Curie temperature is higher at a position closer to the second magnetic layer.The recording method utilizing the recording medium according to the present invention is also disclosed.
    Type: Grant
    Filed: June 7, 1995
    Date of Patent: October 21, 1997
    Assignee: Canon Kabushiki Kaisha
    Inventor: Tsutomu Shiratori
  • Patent number: 5679455
    Abstract: This invention relates to a multi-layer magneto-optic recording medium having an information recording layer and an initializing layer that can be overwritten by light modulation, and in which adjacent layers, including auxiliary layers provided for more efficient transfer from the initializing layer to the recording layer, are coupled by an exchange force. This structure enables high-density, high-speed recording of audio information, visual information, and computer data.
    Type: Grant
    Filed: June 7, 1995
    Date of Patent: October 21, 1997
    Assignee: Mitsubishi Denki Kabushiki Kaisha
    Inventors: Yoshiyuki Nakaki, Takashi Tokunaga, Tatsuya Fukami, Motohisa Taguchi, Kazuhiko Tsutsumi
  • Patent number: 5667862
    Abstract: A magneto-optical disk having a four-layer structure formed of a first protective dielectric layer, a recording magnetic layer, a second protective dielectric layer and a reflective metal layer is disclosed. The constraints for the film thicknesses of the various layers are determined not only from the optical and magneto-optical aspects, but from the aspect of the dynamic thermal response.The recording magnetic layer is a magnetic layer mainly formed of TbFeCo and having a film thickness of not less than 180 .ANG. and not more than 280 .ANG.. The first protective dielectric layer is a nitride film having a film thickness such that the product of its refractive index and the film thickness is not less than 0.2 and not more than 0.35 times the wavelength of the laser light employed. The second protective dielectric layer is a nitride film having a film thickness such that the product of its refractive index and the film thickness is not less than 0.1 and not more than 0.
    Type: Grant
    Filed: April 16, 1991
    Date of Patent: September 16, 1997
    Assignee: Sony Corporation
    Inventors: Yasuaki Nakane, Shuichi Igarashi, Sakuya Tamada, Susumu Sakamoto, Teruo Chiba
  • Patent number: 5665467
    Abstract: A magneto-optical recording medium includes a first magnetic layer, a second magnetic layer and a third magnetic layer respectively made of rare-earth-transition metal alloys which are laminated in this order. The first magnetic layer has a perpendicular magnetization in a temperature range between room temperature and its Curie temperature. The second magnetic layer made of GdFeCo is set such that its Curie temperature is higher than the Curie temperature of the first magnetic layer, coercive force thereof at room temperature is nearly zero, and that it has an in-plane magnetization at room temperature and a transition occurs therein from the in-plane magnetization to the perpendicular magnetization at above a predetermined temperature.
    Type: Grant
    Filed: February 15, 1994
    Date of Patent: September 9, 1997
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Junichiro Nakayama, Michinobu Mieda, Hiroyuki Katayama, Akira Takahashi, Kenji Ohta
  • Patent number: 5662988
    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.
    Type: Grant
    Filed: February 10, 1995
    Date of Patent: September 2, 1997
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Junichiro Nakayama, Hiroyuki Katayama, Akira Takahashi, Kenji Ohta, Yoshiteru Murakami
  • Patent number: 5660929
    Abstract: A perpendicular magnetic recording medium is fabricated based on R.sub.21-60 (Fe.sub.1-y Co.sub.y).sub.z M.sub.0-10 wherein z is balance and at least 70 at % of R is Nd and/or Pr, the balance of R being one or more of other rare earth elements, and wherein y is less than 0.5 by atomic ratio. M is at least one of various additional metal elements. The Curie temperature Tc is between 70.degree. to 250.degree. C.; the saturation magnetization Ms is about 450 emu/cc or more; the uniaxial perpendicular magnetic anisotropy constant Ku of 2.5.times.10.sup.6 erg/cc or more is attained. Kerr rotation angle is 0.3 degree or more, which provides a magneto-optic recording medium. Since light rare earth elements having the collinear alignment of magnetic moment with Fe are used as a key element, it is possible to fabricate uniform perpendicular magnetic anisotropy thin films in a mass production scale at a low cost.
    Type: Grant
    Filed: November 18, 1993
    Date of Patent: August 26, 1997
    Assignee: Sumitomo Special Metals Co., Ltd.
    Inventors: Takao Suzuki, Masato Sagawa
  • Patent number: 5656385
    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.
    Type: Grant
    Filed: July 7, 1993
    Date of Patent: August 12, 1997
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Junsaku Nakajima, Akira Takahashi, Junji Hirokane, Yoshiteru Murakami, Kenji Ohta
  • Patent number: 5648163
    Abstract: A magneto-optic recording medium including a transparent substrate and a magneto-optic stack provided thereon. The stack includes a plurality of magneto-optic film layers less than 10 nm thick. Adjacent magneto-optic film layers are separated by dielectric layers consisting essentially of Y.sub.2 O.sub.3.
    Type: Grant
    Filed: September 27, 1994
    Date of Patent: July 15, 1997
    Assignee: Imation Corp.
    Inventor: Michael B. Hintz
  • Patent number: 5645911
    Abstract: An over-writable method of magnetooptical recording using a magnetooptical recording medium provides a high C/N ratio in a reproduction mode, permits reduction of the intensity of the initial magnetic field at room temperature in a recording mode, and permits reduction of laser beam intensity in a recording mode. First and second magnetic layers having perpendicular magnetic anisotropy serve as a recording layer and as a reference layer, respectively. The second 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-Vwhere U=0 to 50 atomic %V=15 to 35 atomic % andW=1 to 50 atomic %.The medium satisfies certain required conditions.
    Type: Grant
    Filed: May 2, 1995
    Date of Patent: July 8, 1997
    Assignee: Nikon Corporation
    Inventor: Hiroyuki Matsumoto
  • Patent number: 5643650
    Abstract: The recording sensitivity can be improved of a magneto-optical recording medium having a laminar structure consisting of a first dielectric layer, a recording layer, a second dielectric layer and reflecting layer successively formed on a transparent substrate plate by forming the reflecting layer from an alloy consisting of aluminum and from 0.05 to 3 atomic % of a rare earth element such as neodymium and gadolinium in place of pure aluminum as in conventional magneto-optical recording media.
    Type: Grant
    Filed: June 28, 1995
    Date of Patent: July 1, 1997
    Assignee: Shin-Etsu Chemical Co., Ltd.
    Inventors: Yoshio Tawara, Katsushi Tokunaga, Hideo Kaneko, Yoshiaki Shimizu
  • Patent number: 5640374
    Abstract: A recording layer having a recording magnetic domain for recording thereon information is formed. A readout layer for reading the information by the application of a light beam is formed on the recording layer. An intermediate layer made of a film having in-plane magnetization is formed between the recording layer and readout layer to control a magnetic exchange coupling force between the recording layer and readout layer. The readout layer is arranged so that the stable magnetic domain width in the readout layer is larger than that of the recording magnetic domain in the recording layer at room temperature. At a readout temperature achieved by the light beam, the stable magnetic domain width becomes smaller than that of the recording magnetic domain, and the magnetization direction in the recording magnetic domain is copied.
    Type: Grant
    Filed: June 6, 1996
    Date of Patent: June 17, 1997
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Junji Hirokane, Michinobu Mieda, Junichiro Nakayama, Akira Takahashi
  • Patent number: 5637411
    Abstract: Disclosed is a magneto-optical recording medium which comprises a transparent substrate and, provided on the substrate, a magneto-optical recording film comprising a perpendicular magnetic film based on rare earth metal-transition metal and an auxiliary magnetic film having spontaneous magnetization which exerts, between itself and the magneto-optical recording film, an exchange coupling force and wherein the auxiliary magnetic film is a magnetic film which readily rotates its magnetization direction toward the external magnetic field in the neighborhood of the Curie temperature of the magneto-optical recording film and has a squareness ratio of not more than 1 in the neighborhood of the Curie temperature. Also disclosed is a process for producing the magneto-optical recording medium.
    Type: Grant
    Filed: April 14, 1994
    Date of Patent: June 10, 1997
    Assignee: Hitachi Maxell, Ltd.
    Inventors: Katsusuke Shimazaki, Satoru Ohnuki, Masatoshi Hashimoto, Yoshinori Shirai, Norio Ohta, Hideo Fujiwara, Masafumi Yoshihiro, Yukinori Yamada, Eiji Koyama, Hitoshi Furusho
  • Patent number: 5631096
    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.
    Type: Grant
    Filed: March 7, 1995
    Date of Patent: May 20, 1997
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Junsaku Nakajima, Yoshiteru Murakami, Kenji Ohta, Akira Takahashi
  • Patent number: 5627777
    Abstract: A magneto-optical recording medium includes a transparent substrate, a magnetic reproducing layer laminated on the transparent substrate and having an easy direction of magnetization perpendicular to a film surface, a nonmagnetic intermediate layer laminated on the magnetic reproducing layer, and a magnetic recording layer laminated on the nonmagnetic intermediate layer and having an easy direction of magnetization perpendicular to a film surface. When a reproducing laser beam is directed onto the recording medium, a temperature distribution is formed in a beam spot. The temperature distribution consists of a low-temperature region satisfying Hc>Hs and Hc>Hr, an intermediate-temperature region satisfying Hs>Hc and Hs+Hc>Hr, and a high-temperature region satisfying Hr>Hs+Hc, where Hc represents a coercive force of the reproducing layer, Hs represents a magnetostatic bonding force between the reproducing layer and the recording layer, and Hr represents a reproducing magnetic field.
    Type: Grant
    Filed: May 30, 1995
    Date of Patent: May 6, 1997
    Assignee: Fujitsu Limited
    Inventors: Ken Tamanoi, Kenji Shono
  • Patent number: 5626965
    Abstract: A magnetooptical recording medium includes a substrate formed with a guide groove for tracking a laser beam, and first and second magnetic layers which are stacked on the substrate and each of which consists of an amorphous heavy rare earth-transition metal alloy. The first and second magnetic layers are magnetically coupled to each other. The first magnetic layer has a relatively high Curie temperature and a relatively low coercivity at room temperature, and the second magnetic layer has a relatively low Curie temperature and a relatively high coercivity at room temperature. The film thickness t.sub.1 of the first magnetic layer and the film thickness t.sub.2 of the second magnetic layer satisfy a condition t.sub.2 /t.sub.1 .gtoreq.2.5.
    Type: Grant
    Filed: June 7, 1995
    Date of Patent: May 6, 1997
    Assignee: Nikon Corporation
    Inventor: Haruhisa Iida
  • Patent number: 5620767
    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.
    Type: Grant
    Filed: August 9, 1993
    Date of Patent: April 15, 1997
    Assignee: Ricoh Company, Ltd.
    Inventors: Makoto Harigaya, Yukio Ide, Osamu Nonoyama, Yoshiyuki Kageyama, Hiroko Iwasaki
  • Patent number: RE35629
    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.
    Type: Grant
    Filed: October 14, 1993
    Date of Patent: October 14, 1997
    Assignee: Sharp Kabushiki Kaisha
    Inventors: Yoshiteru Murakami, Akira Takahashi, Kazuo Van, Junichiro Nakayama, Hiroyuki Katayama, Kenji Ohta