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).

  • 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
  • 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
  • Patent number: 7372648
    Abstract: A pair of members opposed to each other via a gap are commonly used as an evanescent light probe and a writing magnetic head. When the spacing and width of the gap are smaller than the wavelength ? of injected light, highly intensive evanescent light is generated from the gap position of the opposite surface. Magnetic writing is carried out by applying a recording magnetic field from the pair of members to a medium heated by the evanescent light.
    Type: Grant
    Filed: August 18, 2004
    Date of Patent: May 13, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Junichi Akiyama, Akira Kikitsu, Tadashi Kai, Toshihiko Nagase, Tomoyuki Maeda
  • Publication number: 20080096050
    Abstract: A magnetic recording medium capable of alleviating thermal fluctuation and improving the recording density includes a functional layer containing a magnetic material, and a recording layer overlying the functional layer and containing a magnetic material. The recording layer contains a plurality of magnetic grains and a nonmagnetic material existing among the magnetic grains, and the functional layer and the recording layer exert exchange coupling interaction in a direction making a substantially orthogonal relation with each other at room temperature.
    Type: Application
    Filed: December 11, 2007
    Publication date: April 24, 2008
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Akira KIKITSU, Tadashi Kai, Junichi Akiyama
  • 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: 7330335
    Abstract: A magnetic recording medium capable of alleviating thermal fluctuation and improving the recording density includes a functional layer (12) containing a magnetic material, and a recording layer (11) overlying the functional layer and containing a magnetic material. The recording layer contains a plurality of magnetic grains (51) and a nonmagnetic material (52) existing among the magnetic grains, and the functional layer and the recording layer exert exchange coupling interaction in a direction making a substantially orthogonal relation with each other at the room temperature.
    Type: Grant
    Filed: September 22, 2004
    Date of Patent: February 12, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Akira Kikitsu, Tadashi Kai, Junichi Akiyama
  • Patent number: 7326982
    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: September 3, 2004
    Date of Patent: February 5, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Yoshihisa Iwata, Yoshiaki Fukuzumi, Tadashi Kai
  • Publication number: 20070297220
    Abstract: A magnetoresistive includes a first magnetic reference layer having a fixed magnetization direction, a magnetic free layer having a magnetization direction which is changeable by being supplied with spin polarized electrons, a second magnetic reference layer having a fixed magnetization direction, a first intermediate layer provided between the first magnetic reference layer and the magnetic free layer, and a second intermediate layer provided between the magnetic free layer and the second magnetic reference layer. The magnetic free layer and the first magnetic reference layer have directions of easy magnetization perpendicular or parallel to an in-plane direction. The first magnetic reference layer and the second magnetic reference layer have directions of easy magnetization perpendicular to each other.
    Type: Application
    Filed: January 23, 2007
    Publication date: December 27, 2007
    Inventors: Masatoshi YOSHIKAWA, Tadashi Kai, Toshihiko Nagase, Tatsuya Kishi, Hiroaki Yoda
  • Publication number: 20070211522
    Abstract: A magnetic random access memory according to an embodiment of the present invention comprises first and second write lines which cross each other, and a magnetoresistive element whose center point is not overlapped onto a cross portion of the first and second write lines, wherein a center line of the magnetoresistive element in a direction of easy magnetization and center lines of the first and second write lines form a triangle.
    Type: Application
    Filed: June 20, 2006
    Publication date: September 13, 2007
    Inventors: Yoshiaki Fukuzumi, Tadashi Kai
  • 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
  • Publication number: 20070086121
    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/(6nAt)}. Jw is a write current density, t is a thickness of the free layer, A is a constant.
    Type: Application
    Filed: September 22, 2006
    Publication date: April 19, 2007
    Inventors: Toshihiko Nagase, Masatoshi Yoshikawa, Eiji Kitagawa, Masahiko Nakayama, Tadashi Kai, Tatsuya Kishi, Hiroaki Yoda
  • Publication number: 20070070689
    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: March 20, 2006
    Publication date: March 29, 2007
    Inventors: Sumio Ikegawa, Masahiko Nakayama, Tadashi Kai, Eiji Kitagawa, Hiroaki Yoda
  • Patent number: 7190613
    Abstract: An MTJ element has two magnetic layers and a nonmagnetic layer. The resistance of the MTJ element, which varies depending on whether the two magnetic layers are magnetized parallel or antiparallel. In an MRAM adapted to write data into the MTJ element by causing a write wiring to generate induced magnetic flux and consequently changing the direction of magnetization of the recording layer, the MTJ element is a perpendicular MTJ element in which each of the two magnetic layers is magnetized in a direction perpendicular to its plane. The write wiring is placed in a direction perpendicular to the direction of the thickness of the MTJ element and applies a generated magnetic field to the magnetic layers of the MTJ element in the direction in which they are magnetized. Magnetic yokes hold the MTJ element in the direction of its thickness.
    Type: Grant
    Filed: June 8, 2004
    Date of Patent: March 13, 2007
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Toshihiko Nagase, Hiroaki Yoda, Masatoshi Yoshikawa, Tadashi Kai, Tatsuya Kishi, Hisanori Aikawa, Tomomasa Ueda
  • Publication number: 20070013015
    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: March 20, 2006
    Publication date: January 18, 2007
    Inventors: Tadashi Kai, Masahiko Nakayama, Sumio Ikegawa, Yoshiaki Fukuzumi, Yoshihisa Iwata
  • Publication number: 20070012972
    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: March 27, 2006
    Publication date: January 18, 2007
    Inventors: Masahiko Nakayama, Tadashi Kai, Sumio Ikegawa, Yoshiaki Fukuzumi, Tatsuya Kishi
  • Publication number: 20060198184
    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: Application
    Filed: October 21, 2005
    Publication date: September 7, 2006
    Inventors: Hiroaki Yoda, Tadashi Kai, Masahiko Nakayama, Sumio Ikegawa, Tatsuya Kishi
  • Patent number: 7084447
    Abstract: A magnetic random access memory includes a magnetoresistive element which has a recording layer, a fixed layer, and an intermediate nonmagnetic layer, the recording layer comprising a first ferromagnetic layer formed on the intermediate nonmagnetic layer, a first nonmagnetic layer formed on the first ferromagnetic layer, a second ferromagnetic layer formed on the first nonmagnetic layer and magnetically coupled with the first ferromagnetic layer by first magnetic coupling, a second nonmagnetic layer formed on the second ferromagnetic layer, and a third ferromagnetic layer formed on the second nonmagnetic layer and magnetically coupled with the second ferromagnetic layer by second magnetic coupling, wherein one of a state in which the first magnetic coupling is anti-ferromagnetic coupling and the second magnetic coupling is ferromagnetic coupling, and a state in which the first magnetic coupling is ferromagnetic coupling and the second magnetic coupling is anti-ferromagnetic coupling is obtained.
    Type: Grant
    Filed: December 9, 2004
    Date of Patent: August 1, 2006
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Yoshiaki Fukuzumi, Tadashi Kai
  • Publication number: 20060114716
    Abstract: There is provided a magnetoresistance element including a free layer that includes a first ferromagnetic layer and a second ferromagnetic layer whose magnetization directions are equal to each other and a nonmagnetic film intervening between the first and second ferromagnetic layers, a pinned layer including a third ferromagnetic layer that faces the free layer, and a nonmagnetic layer intervening between the free layer and the pinned layer, the nonmagnetic film containing a material selected from the group including titanium, vanadium, zirconium, niobium, molybdenum, technetium, hafnium, tungsten, rhenium, alloys thereof, semiconductors and insulators.
    Type: Application
    Filed: January 20, 2006
    Publication date: June 1, 2006
    Inventors: Tadashi Kai, Toshihiko Nagase, Tatsuya Kishi, Yoshiaki Saito
  • Patent number: 7054087
    Abstract: A magnetic recording-reproducing apparatus has a magnetic recording medium having a nonmagnetic substrate, and a functional layer and a recording layer formed on the nonmagnetic substrate, the recording layer exhibiting a magnetic anisotropy energy density KuRL, the functional layer developing ferromagnetism upon irradiation with light so as to exhibit a magnetic anisotropy energy density KuFL lower than the magnetic anisotropy energy density KuRL and the functional layer serving to lower the magnetic anisotropy energy density of the recording layer through exchange coupling interaction with the recording layer when the functional layer is irradiated with light, a light source which irradiates the functional layer with light, and a magnetic head having a writing head writing signal magnetization by applying a magnetic field to the recording layer and a reading head reading the signal magnetization recorded in the recording layer.
    Type: Grant
    Filed: September 21, 2004
    Date of Patent: May 30, 2006
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Tadashi Kai, Akira Kikitsu, Toshihiko Nagase, Tomoyuki Maeda, Junichi Akiyama
  • Publication number: 20060082933
    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: Application
    Filed: October 6, 2005
    Publication date: April 20, 2006
    Inventors: Tatsuya Kishi, Masahiko Nakayama, Yoshiaki Fukuzumi, Tadashi Kai