Patents by Inventor Sumio Ikegawa

Sumio Ikegawa 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).

  • Publication number: 20100073998
    Abstract: A data writing method for a magnetoresistive effect element of an aspect of the present invention including generating a write current in which a falling period from the start of a falling edge to the end of the falling edge is longer than a rising period from the start of a rising edge to the end of the rising edge, and flowing the write current through the magnetoresistive effect element which comprises a first magnetic layer having an invariable magnetizing direction, a second magnetic layer having a variable magnetizing direction, and a tunnel barrier layer provided between the first magnetic layer and the second magnetic layer, to change the magnetizing direction of the second magnetic layer.
    Type: Application
    Filed: September 17, 2009
    Publication date: March 25, 2010
    Inventors: Masahiko NAKAYAMA, Hisanori Aikawa, Tsuneo Inaba, Kenji Tsuchida, Sumio Ikegawa, Hiroaki Yoda, Naoharu Shimomura
  • 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
  • Publication number: 20090225587
    Abstract: A magnetoresistive element includes a first magnetic layer which includes a first surface and a second surface and has a first standard electrode potential, a second magnetic layer, a barrier layer which is provided between the second magnetic layer and the first surface of the first magnetic layer, and a nonmagnetic cap layer which contacts the second surface of the first magnetic layer and is formed from an alloy of a first metal material and a second metal material, the first metal material having a second standard electrode potential lower than the first standard electrode potential, the second metal material having a third standard electrode potential higher than the first standard electrode potential.
    Type: Application
    Filed: May 22, 2009
    Publication date: September 10, 2009
    Inventors: Makoto Nagamine, Toshihiko Nagase, Sumio Ikegawa, Katsuya Nishiyama, Masatoshi Yoshikawa
  • 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: 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
  • 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
  • Publication number: 20080253039
    Abstract: A magnetoresistive effect element includes a first ferromagnetic layer formed above a substrate, a second ferromagnetic layer formed above the first ferromagnetic layer, an insulating layer interposed between the first ferromagnetic layer and the second ferromagnetic layer and formed of a metal oxide, and a first nonmagnetic metal layer interposed between the insulating layer and the second ferromagnetic layer and in contact with a surface of the insulating layer on the side of the second ferromagnetic layer, the first nonmagnetic metal layer containing the same metal element as the metal oxide.
    Type: Application
    Filed: April 9, 2008
    Publication date: October 16, 2008
    Inventors: Makoto NAGAMINE, Keiji HOSOTANI, Hisanori AIKAWA, Tomomasa UEDA, Sumio IKEGAWA
  • 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: 20080180859
    Abstract: A magnetoresistive element includes: a magnetization free layer having a first plane and a second plane located on the opposite side from the first plane, and having a variable magnetization direction; a magnetization pinned layer provided on the first plane side of the magnetization free layer, and having a pinned magnetization direction; a first tunnel barrier layer provided between the magnetization free layer and the magnetization pinned layer; a second tunnel barrier layer provided on the second plane of the magnetization free layer; and a non-magnetic layer provided on a plane on the opposite side of the second tunnel barrier layer from the magnetization free layer. The magnetization direction of the magnetization free layer is variable by applying current between the magnetization pinned layer and the non-magnetic layer, and a resistance ratio between the first tunnel barrier layer and the second tunnel barrier layer is in a range of 1:0.25 to 1:4.
    Type: Application
    Filed: January 15, 2008
    Publication date: July 31, 2008
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Tomomasa UEDA, Hisanori AIKAWA, Masatoshi YOSHIKAWA, Naoharu SHIMOMURA, Masahiko NAKAYAMA, Sumio IKEGAWA, Keiji HOSOTANI, Makoto NAGAMINE
  • 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
  • Publication number: 20080130176
    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: Application
    Filed: January 25, 2008
    Publication date: June 5, 2008
    Applicant: KABUSHHIKI KAISHA TOSHIBA
    Inventors: Tadashi KAI, Masahiko Nakayama, Sumio Ikegawa, Yoshiaki Fukuzumi, Yoshihisa Iwata
  • Publication number: 20080131732
    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: January 25, 2008
    Publication date: June 5, 2008
    Inventors: Masahiko NAKAYAMA, Tadashi Kai, Tatsuya Kishi, Yoshiaki Fukuzumi, Toshihiko Nagase, Sumio Ikegawa, Hiroaki Yoda
  • Patent number: 7355884
    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: October 7, 2005
    Date of Patent: April 8, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Masahiko Nakayama, Tadashi Kai, Tatsuya Kishi, Yoshiaki Fukuzumi, Toshihiko Nagase, Sumio Ikegawa, Hiroaki Yoda
  • Patent number: 7266011
    Abstract: The magnetic memory includes a plurality of memory cells, each memory cell including: at least one writing wire; at least one data storage portion, provided on at least one portion of an outer periphery of the writing wire, which comprises a ferromagnetic material whose magnetization direction can be inverted by causing a current to flow in the writing wire; and at least one magneto-resistance effect element, disposed in the vicinity of the data storage portion, which senses the magnetization direction of the data storage portion.
    Type: Grant
    Filed: March 7, 2006
    Date of Patent: September 4, 2007
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Minoru Amano, Tatsuya Kishi, Sumio Ikegawa, Yoshiaki Saito, Hiroaki Yoda
  • Patent number: 7245524
    Abstract: A magnetic memory device includes a first write wiring which runs in a first direction, a second write wiring which runs in a second direction different from the first direction, and a magnetoresistive element which is arranged at an intersection between the first and second write wirings, has a fixed layer, a recording layer, and a magnetoresistive layer sandwiched between the fixed layer and the recording layer, and has an axis of easy magnetization obliquely with respect to the first and second directions, the recording layer including a first ferromagnetic layer, a second ferromagnetic layer, and a first nonmagnetic layer sandwiched between the first and second ferromagnetic layers, in which first magnetization of the first ferromagnetic layer and second magnetization of the second ferromagnetic layer are ferromagnetically coupled, and a ferro-coupling constant C of a ferromagnetic coupling is 0.0001 erg/cm2?C?0.2 erg/cm2.
    Type: Grant
    Filed: October 21, 2005
    Date of Patent: July 17, 2007
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Hiroaki Yoda, Tadashi Kai, Masahiko Nakayama, Sumio Ikegawa, Tatsuya Kishi
  • Patent number: 7203088
    Abstract: The number of read errors can be reduced, and a large read signal can be produced.
    Type: Grant
    Filed: March 1, 2005
    Date of Patent: April 10, 2007
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Sumio Ikegawa, Yoshihisa Iwata, Kenji Tsuchida