Patents by Inventor Tadashi Kai

Tadashi Kai has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 7663197
    Abstract: A magnetoresistive element which records information by supplying spin-polarized electrons to a magnetic material, includes a first pinned layer which is made of a magnetic material and has a first magnetization directed in a direction perpendicular to a film surface, a free layer which is made of a magnetic material and has a second magnetization directed in the direction perpendicular to the film surface, the direction of the second magnetization reversing by the spin-polarized electrons, and a first nonmagnetic layer which is provided between the first pinned layer and the free layer. A saturation magnetization Ms of the free layer satisfies a relationship 0?Ms<?{square root over ( )}{Jw/(6?At)}. Jw is a write current density, t is a thickness of the free layer, A is a constant.
    Type: Grant
    Filed: September 22, 2006
    Date of Patent: February 16, 2010
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Toshihiko Nagase, Masatoshi Yoshikawa, Eiji Kitagawa, Masahiko Nakayama, Tadashi Kai, Tatsuya Kishi, Hiroaki Yoda
  • Patent number: 7599156
    Abstract: A magnetoresistive element according to an example of the present invention has a stacked structure comprised first and second ferromagnetic layers and a nonmagnetic layer disposed between these ferromagnetic layers, and a planar shape of at least one of the first and second ferromagnetic layers has a shape formed by combining two or more parts each having a shape of a character C.
    Type: Grant
    Filed: October 6, 2005
    Date of Patent: October 6, 2009
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Tatsuya Kishi, Masahiko Nakayama, Yoshiaki Fukuzumi, Tadashi Kai
  • Publication number: 20090244792
    Abstract: A magnetoresistance effect element includes: a first ferromagnetic layer having invariable magnetization perpendicular to a film plane; a second ferromagnetic layer having variable magnetization perpendicular to the film plane; a first nonmagnetic layer interposed between the first ferromagnetic layer and the second ferromagnetic layer; a third ferromagnetic layer provided on an opposite side of the second ferromagnetic layer from the first nonmagnetic layer, and having variable magnetization parallel to the film plane; and a second nonmagnetic layer interposed between the second and third ferromagnetic layers.
    Type: Application
    Filed: March 3, 2009
    Publication date: October 1, 2009
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Masahiko NAKAYAMA, Tadashi KAI, Sumio IKEGAWA, Hiroaki YODA, Tatsuya KISHI
  • Patent number: 7592189
    Abstract: A magnetic memory device comprising, a magneto-resistance effect element that is provided at an intersection between a first write line and a second write line. And the magneto-resistance effect element having, an easy axis that extends in a direction of extension of the first write line, and a first conductive layer for electrical connection to the magneto-resistance effect element, the first conductive layer having sides which are in flush with sides of the magneto-resistance effect element.
    Type: Grant
    Filed: November 6, 2007
    Date of Patent: September 22, 2009
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Yoshihisa Iwata, Yoshiaki Fukuzumi, Tadashi Kai
  • Publication number: 20090224342
    Abstract: A magnetoresistive effect element includes a reference layer, a recording layer, and a nonmagnetic layer. The reference layer is made of a magnetic material, has an invariable magnetization which is perpendicular to a film surface. The recording layer is made of a magnetic material, has a variable magnetization which is perpendicular to the film surface. The nonmagnetic layer is arranged between the reference layer and the recording layer. A critical diameter which is determined by magnetic anisotropy, saturation magnetization, and switched connection of the recording layer and has a single-domain state as a unique stable state or a critical diameter which has a single-domain state as a unique stable state and is inverted while keeping the single-domain state in an inverting process is larger than an element diameter of the magnetoresistive effect element.
    Type: Application
    Filed: October 9, 2008
    Publication date: September 10, 2009
    Inventors: Masahiko NAKAYAMA, Kay Yakushiji, Sumio Ikegawa, Shinji Yuasa, Tadashi Kai, Toshihiko Nagase, Minoru Amano, Hisanori Aikawa, Tatsuya Kishi, Hiroaki Yoda
  • Publication number: 20090166322
    Abstract: A magneto-resistive element according to an aspect of the present invention includes a free layer whose magnetized state changes and a pinned layer whose magnetized state is fixed. The free layer comprises first and second ferromagnetic layers and a non-magnetic layer which is arranged between the first and second ferromagnetic layers. An intensity of exchange coupling between the first and second ferromagnetic layers is set so that an astroid curve in a hard axis direction opens.
    Type: Application
    Filed: January 29, 2009
    Publication date: July 2, 2009
    Inventors: Sumio IKEGAWA, Masahiko Nakayama, Tadashi Kai, Eiji Kitagawa, Hiroaki Yoda
  • Publication number: 20090140358
    Abstract: A magnetoresistive element includes a first ferromagnetic layer having a first magnetization, the first magnetization having a first pattern when the magnetoresistive element is half-selected during a first data write, a second pattern when the magnetoresistive element is selected during a second data write, and a third pattern of residual magnetization, the first pattern being different from the second and third pattern, a second ferromagnetic layer having a second magnetization, and a nonmagnetic layer arranged between the first ferromagnetic layer and the second ferromagnetic layer and having a tunnel conductance changing dependent on a relative angle between the first magnetization and the second magnetization.
    Type: Application
    Filed: February 2, 2009
    Publication date: June 4, 2009
    Inventors: Masahiko Nakayama, Tadashi Kai, Tatsuya Kishi, Yoshiaki Fukuzumi, Toshihiko Nagase, Sumio Ikegawa, Hiroaki Yoda
  • Patent number: 7525837
    Abstract: A magnetoresistive effect element includes a nonmagnetic layer having mutually facing first and second surfaces. A reference layer is provided on the first surface and has a fixed magnetization direction. A magnetization variable layer is provided on the second surface, has variable magnetization direction, and has a planer shape including a rectangular part, a first projected part, and a second projected part. The rectangular part has mutually facing first and second longer sides and mutually facing first and second shorter sides. The first projected part projects from the first longer side at a position shifted from the center toward the first shorter side. The second projected part projects from the second longer side at a position shifted from the center toward the second shorter side.
    Type: Grant
    Filed: January 25, 2008
    Date of Patent: April 28, 2009
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Tadashi Kai, Masahiko Nakayama, Sumio Ikegawa, Yoshiaki Fukuzumi, Yoshihisa Iwata
  • Patent number: 7518907
    Abstract: A magnetoresistive element includes a first ferromagnetic layer having a first magnetization, the first magnetization having a first pattern when the magnetoresistive element is half-selected during a first data write, a second pattern when the magnetoresistive element is selected during a second data write, and a third pattern of residual magnetization, the first pattern being different from the second and third pattern, a second ferromagnetic layer having a second magnetization, and a nonmagnetic layer arranged between the first ferromagnetic layer and the second ferromagnetic layer and having a tunnel conductance changing dependent on a relative angle between the first magnetization and the second magnetization.
    Type: Grant
    Filed: January 25, 2008
    Date of Patent: April 14, 2009
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Masahiko Nakayama, Tadashi Kai, Tatsuya Kishi, Yoshiaki Fukuzumi, Toshihiko Nagase, Sumio Ikegawa, Hiroaki Yoda
  • Patent number: 7518906
    Abstract: A magneto-resistive element according to an aspect of the present invention includes a free layer whose magnetized state changes and a pinned layer whose magnetized state is fixed. The free layer comprises first and second ferromagnetic layers and a non-magnetic layer which is arranged between the first and second ferromagnetic layers. An intensity of exchange coupling between the first and second ferromagnetic layers is set so that an astroid curve in a hard axis direction opens.
    Type: Grant
    Filed: March 20, 2006
    Date of Patent: April 14, 2009
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Sumio Ikegawa, Masahiko Nakayama, Tadashi Kai, Eiji Kitagawa, Hiroaki Yoda
  • Publication number: 20090080239
    Abstract: A magnetoresistive element includes a first reference layer having magnetic anisotropy perpendicular to a film surface, and an invariable magnetization, a recording layer having a stacked structure formed by alternately stacking magnetic layers and nonmagnetic layers, magnetic anisotropy perpendicular to a film surface, and a variable magnetization, and an intermediate layer provided between the first reference layer and the recording layer, and containing a nonmagnetic material. The magnetic layers include a first magnetic layer being in contact with the intermediate layer and a second magnetic layer being not in contact with the intermediate layer. The first magnetic layer contains an alloy containing cobalt (Co) and iron (Fe), and has a film thickness larger than that of the second magnetic layer.
    Type: Application
    Filed: September 18, 2008
    Publication date: March 26, 2009
    Inventors: Toshihiko Nagase, Katsuya Nishiyama, Tadashi Kai, Masahiko Nakayama, Makoto Nagamine, Minoru Amano, Masatoshi Yoshikawa, Tatsuya Kishi, Hiroaki Yoda
  • Publication number: 20090052095
    Abstract: A magnetic recording head includes: a main magnetic pole; a laminated body; and a pair of electrodes. The laminated body includes a first magnetic layer having a coercivity lower than magnetic field applied by the main magnetic pole, a second magnetic layer having a coercivity lower than the magnetic field applied by the main magnetic pole, and an intermediate layer provided between the first magnetic layer and the second magnetic layer. The pair of electrodes are operable to pass a current through the laminated body.
    Type: Application
    Filed: June 2, 2008
    Publication date: February 26, 2009
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Kenichiro Yamada, Hitoshi Iwasaki, Junichi Akiyama, Masayuki Takagishi, Tomomi Funayama, Masahiro Takashita, Mariko Shimizu, Shuichi Murakami, Tadashi Kai
  • Patent number: 7470963
    Abstract: There are provided a first reference layer, in which a direction of magnetization is fixed, and a storage layer including a main body, in which a length in an easy magnetization axis direction is longer than a length in a hard magnetization axis direction, and a projecting portion provided to a central portion of the main body in the hard magnetization axis direction, a direction of magnetization of the storage layer being changeable in accordance with an external magnetic field.
    Type: Grant
    Filed: August 30, 2005
    Date of Patent: December 30, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Tadashi Kai, Shigeki Takahashi, Tomomasa Ueda, Tatsuya Kishi, Yoshiaki Saito
  • Publication number: 20080291585
    Abstract: It is made possible to provide a magnetoresistive effect element that can reverse magnetization direction with a low current, having low areal resistance (RA) and a high TMR ratio. A magnetoresistive effect element includes: a film stack that includes a magnetization free layer including a magnetic layer in which magnetization direction is changeable, a magnetization pinned layer including a magnetic layer in which magnetization direction is pinned, and an intermediate layer provided between the magnetization free layer and the magnetization pinned layer, the intermediate layer being an oxide containing boron (B) and an element selected from the group consisting of Ca, Mg, Sr, Ba, Ti, and Sc. Current is applied bidirectionally between the magnetization pinned layer and the magnetization free layer through the intermediate layer, so that the magnetization of the magnetization free layer is reversible.
    Type: Application
    Filed: August 23, 2007
    Publication date: November 27, 2008
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Masatoshi Yoshikawa, Tadashi Kai, Toshihiko Nagase, Eiji Kitagawa, Tatsuya Kishi, Hiroaki Yoda
  • Publication number: 20080261331
    Abstract: A magnetic memory device comprising, a magneto-resistance effect element that is provided at an intersection between a first write line and a second write line. And the magneto-resistance effect element having, an easy axis that extends in a direction of extension of the first write line, and a first conductive layer for electrical connection to the magneto-resistance effect element, the first conductive layer having sides which are in flush with sides of the magneto-resistance effect element.
    Type: Application
    Filed: November 6, 2007
    Publication date: October 23, 2008
    Inventors: Yoshihisa Iwata, Yoshiaki Fukuzumi, Tadashi Kai
  • Publication number: 20080253174
    Abstract: A magnetoresistive effect element includes a first magnetic layer, a second magnetic layer, and a first spacer layer. The first magnetic layer has an invariable magnetization direction. The second magnetic layer has a variable magnetization direction, and contains at least one element selected from Fe, Co, and Ni, at least one element selected from Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, and Au, and at least one element selected from V, Cr, and Mn. The spacer layer is formed between the first magnetic layer and the second magnetic layer, and made of a nonmagnetic material. A bidirectional electric current flowing through the first magnetic layer, the spacer layer, and the second magnetic layer makes the magnetization direction of the second magnetic layer variable.
    Type: Application
    Filed: March 13, 2008
    Publication date: October 16, 2008
    Inventors: Masatoshi YOSHIKAWA, Eiji Kitagawa, Tadashi Kai, Toshihiko Nagase, Tatsuya Kishi, Hiroaki Yoda
  • Publication number: 20080231998
    Abstract: A magnetoresistive effect element includes a magnetization fixed layer having substantially fixed magnetization direction. A magnetization variable layer has a variable magnetization direction, consists of a magnetic alloy that has a BCC structure and is expressed by Fe1-x-yCoxNiy (0?x+y?1, 0?x?1, 0?y?1), and contains at least one additive element of V, Cr, and Mn in a range of 0<a?20 at % (a is a content). An intermediate layer is disposed between the magnetization fixed layer and the magnetization variable layer and consists of a nonmagnetic material. The magnetization direction of the magnetization variable layer is switched by a bidirectional current passing through the magnetization fixed layer, the intermediate layer, and the magnetization variable layer.
    Type: Application
    Filed: September 20, 2007
    Publication date: September 25, 2008
    Inventors: Masatoshi YOSHIKAWA, Tadashi Kai, Toshihiko Nagase, Eiji Kitagawa, Tatsuya Kishi, Hiroaki Yoda
  • Patent number: 7414880
    Abstract: A magnetoresistive effect element includes a nonmagnetic layer having mutually facing first and second surfaces. A reference layer is provided on the first surface and has a fixed magnetization direction. A magnetization variable layer is provided on the second surface, has variable magnetization direction, and has a planer shape including a rectangular part, a first projected part, and a second projected part. The rectangular part has mutually facing first and second longer sides and mutually facing first and second shorter sides. The first projected part projects from the first longer side at a position shifted from the center toward the first shorter side. The second projected part projects from the second longer side at a position shifted from the center toward the second shorter side.
    Type: Grant
    Filed: March 20, 2006
    Date of Patent: August 19, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Tadashi Kai, Masahiko Nakayama, Sumio Ikegawa, Yoshiaki Fukuzumi, Yoshihisa Iwata
  • Patent number: 7411263
    Abstract: A magnetic memory device includes a magnetoresistive element and a first wiring layer. The magnetoresistive element includes a fixed layer, a recording layer, and a non-magnetic layer interposed therebetween. The first wiring layer extends in a first direction and generates a magnetic field for recording data in the magnetoresistive element. The recording layer includes a base portion extending in a second direction rotated from the first direction by an angle falling within a range of more than 0° to not more than 20°, and first and second projections projecting from the first and second sides of the base portion in a third direction perpendicular to the second direction. The third and fourth sides of the base portion are inclined with respect to the third direction in the same rotational direction as a rotational direction in which the second direction is rotated.
    Type: Grant
    Filed: March 27, 2006
    Date of Patent: August 12, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Masahiko Nakayama, Tadashi Kai, Sumio Ikegawa, Yoshiaki Fukuzumi, Tatsuya Kishi
  • Publication number: 20080158740
    Abstract: A magnetic memory device includes a magnetoresistive element and a first wiring layer. The magnetoresistive element includes a fixed layer, a recording layer, and a non-magnetic layer interposed therebetween. The first wiring layer extends in a first direction and generates a magnetic field for recording data in the magnetoresistive element. The recording layer includes a base portion extending in a second direction rotated from the first direction by an angle falling within a range of more than 0° to not more than 20°, and first and second projections projecting from the first and second sides of the base portion in a third direction perpendicular to the second direction. The third and fourth sides of the base portion are inclined with respect to the third direction in the same rotational direction as a rotational direction in which the second direction is rotated.
    Type: Application
    Filed: February 26, 2008
    Publication date: July 3, 2008
    Inventors: Masahiko NAKAYAMA, Tadashi Kai, Sumio Ikegawa, Yoshiaki Fukuzumi, Tatsuya Kishi