Patents by Inventor Shoji Ikeda

Shoji Ikeda 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: 20130288398
    Abstract: [Object] To provide a method of manufacturing a perpendicular magnetization-type magnetic element, which does not need a step of depositing MgO. [Solving Means] The method of manufacturing a magnetoresistive element 1 according to the present invention includes laminating a first layer 30 on a base 10, the first layer 30 including a material containing at least one of Co, Ni, and Fe. Next, a second layer 40 is laminated on the first layer 30, the second layer 40 including Mg. Next, the Mg in the second layer 40 is oxidized to form MgO by applying an oxidation treatment to a laminated body including the first layer 30 and the second layer 40. Next, the second layer 40 is crystallized by applying a heat treatment to the laminated body, and the first layer 30 is caused to be perpendicularly magnetized. According to the manufacturing method, it is possible to manufacture a perpendicular magnetization-type CoFeB—MgO magnetic element without causing a problem arising from the deposition of MgO.
    Type: Application
    Filed: December 20, 2011
    Publication date: October 31, 2013
    Applicants: TOHOKU UNIVERSITY, ULVAC, INC.
    Inventors: Hiroki Yamamoto, Tadashi Morita, Hideo Ohno, Shoji Ikeda
  • Publication number: 20130141966
    Abstract: Provided are a magnetoresistance effect element with a stable magnetization direction perpendicular to film plane and a controlled magnetoresistance ratio, in which writing can be performed by magnetic domain wall motion, and a magnetic memory including the magnetoresistance effect element. The magnetoresistance ratio is controlled by forming a ferromagnetic layer of the magnetoresistance effect element from a ferromagnetic material including at least one type of 3d transition metal or a Heusler alloy. The magnetization direction is changed from a direction in the film plane to a direction perpendicular to the film plane by controlling the film thickness of the ferromagnetic layer on an atomic layer level.
    Type: Application
    Filed: May 26, 2011
    Publication date: June 6, 2013
    Inventors: Hideo Ohno, Shoji Ikeda, Fumihiro Matsukura, Masaki Endoh, Shun Kanai, Katsuya Miura, Hiroyuki Yamamoto
  • Publication number: 20130107616
    Abstract: A magnetoresistive effect element is provided that exhibits a low writing current density while maintaining a high TMR ratio. A laminated structure of a second ferromagnetic layer/a non-magnetic layer/a first ferromagnetic layer is employed as a recording layer. A material of bcc crystalline structure, such as CoFeB, is employed as a second ferromagnetic layer being in contact with MgO barrier layer. A material whose anisotropy field Hk? in the perpendicular direction is large and that satisfies the relationship of 2?rMs<Hk?<4?Ms is employed as a first ferromagnetic layer. Although a magnetic easy axis of the first ferromagnetic layer lies in-plane, it has a high perpendicular anisotropy field of half or more of the demagnetizing field in the perpendicular direction. Therefore, the effective demagnetizing field in the perpendicular direction is reduced, and a writing current density can be reduced.
    Type: Application
    Filed: July 9, 2010
    Publication date: May 2, 2013
    Inventors: Hideo Ohno, Shoji Ikeda, Hiroyuki Yamamoto, Kenchi Ito, Hiromasa Takahashi
  • Publication number: 20130094284
    Abstract: Provided are a magneto resistive effect element with a stable magnetization direction perpendicular to a film plane and with a controlled magnetoresistance ratio, and a magnetic memory using the magneto resistive effect element. Ferromagnetic layers 106 and 107 of the magneto resistive effect element are formed from a ferromagnetic material containing at least one type of 3d transition metal such that the magnetoresistance ratio is controlled, and the film thickness of the ferromagnetic layers is controlled on an atomic layer level such that the magnetization direction is changed from a direction in the film plane to a direction perpendicular to the film plane.
    Type: Application
    Filed: May 31, 2011
    Publication date: April 18, 2013
    Inventors: Hideo Ohno, Shoji Ikeda, Fumihiro Matsukura, Masaki Endoh, Shun Kanai, Hiroyuki Yamamoto, Katsuya Miura
  • Publication number: 20130058156
    Abstract: A relation between a drive current of a selection transistor of a magnetic memory and a threshold magnetization switching current of the magnetoresistance effect element is optimized. In order to optimize the relation between the drive current of the selection transistor and the threshold magnetization switching current of the magnetoresistance effect element 101 of the magnetic memory cell, a mechanism 601-604 for dropping the threshold magnetization switching current on “1” writing is provided that applies a magnetic field that is in the inverse direction of the pinned layer to the recording layer of the magnetoresistance effect element.
    Type: Application
    Filed: February 17, 2011
    Publication date: March 7, 2013
    Inventors: Hideo Ohno, Shoji Ikeda, Katsuya Miura, Kazuo Ono
  • Publication number: 20130028013
    Abstract: Provided is a magnetoresistive effect element which uses a perpendicularly magnetized material and has a high TMR ratio. Intermediate layers 31, 32 composed of an element metal having a melting point of 1600° C. or an alloy containing the metal on an outside of a structure consisting of a CoFeB layer 41, an MgO barrier layer 10, and a CoFeB layer 42. By inserting the intermediate layers 31, 32, crystallization of the CoFeB layer during annealing is advanced from an MgO (001) crystal side, so that the CoFeB layer has a crystalline orientation in bcc (001).
    Type: Application
    Filed: January 25, 2011
    Publication date: January 31, 2013
    Inventors: Shoji Ikeda, Hideo Ohno, Hiroyuki Yamamoto, Kenchi Ito, Hiromasa Takahashi
  • Publication number: 20120320666
    Abstract: There is provided a magnetoresistive element whose magnetization direction is stable in a direction perpendicular to the film surface and whose magnetoresistance ratio is controlled, as well as magnetic memory using such a magnetoresistive element. By having the material of a ferromagnetic layer forming the magnetoresistive element comprise a ferromagnetic material containing at least one type of 3d transition metal, or a Heusler alloy, to control the magnetoresistance ratio, and by controlling the thickness of the ferromagnetic layer on an atomic layer level, the magnetization direction is changed from being in-plane with the film surface to being perpendicular to the film surface.
    Type: Application
    Filed: February 14, 2011
    Publication date: December 20, 2012
    Applicants: Tohoku University, Hitachi, Ltd.
    Inventors: Hideo Ohno, Shoji Ikeda, Fumihiro Matsukura, Masaki Endoh, Shun Kanai, Katsuya Miura, Hiroyuki Yamamoto
  • Publication number: 20120300543
    Abstract: In magnetic tunnel junctions manufactured with use of a ferromagnetic material having perpendicular magnetic anisotropy, a difference in record retention time depending on stored information due to an imbalance in thermal stability between a parallel state and an anti-parallel state of magnetization, which correspond to bit information, is alleviated. A reference layer and a recording layer which constitute a magnetic tunnel junction are made different in area from each other so as to correct the difference in record retention time corresponding to stored information.
    Type: Application
    Filed: May 24, 2012
    Publication date: November 29, 2012
    Inventors: Hideo Ohno, Shoji Ikeda, Michihiko Yamanouchi, Hideo Sato, Katsuya Miura
  • Patent number: 8274818
    Abstract: Provided is a high-speed and ultra-low-power-consumption nonvolatile memory having a high temperature stability at a zero magnetic field. In a tunnel magnetoresistive film constituting a nonvolatile magnetic memory that employs a writing method using a spin-transfer torque, an insulating layer and a nonmagnetic conductive layer are stacked above a ferromagnetic free layer.
    Type: Grant
    Filed: August 5, 2008
    Date of Patent: September 25, 2012
    Assignees: Tohoku University, Hitachi, Ltd.
    Inventors: Hideo Ohno, Shoji Ikeda, Young Min Lee, Jun Hayakawa
  • Patent number: 8217477
    Abstract: Provided is a reliable nonvolatile memory with a lower power consumption. A ferromagnetic interconnection which is magnetized antiparallel or parallel to a magnetization direction of a ferromagnetic pinned layer in a giant magnetoresistive device or a tunnel magnetoresistive device constituting the magnetic memory cell, is connected to a ferromagnetic free layer with a non-magnetic layer being interposed in between, the ferromagnetic free layer serving as a recording layer. Thereby, the magnetization of the recording layer is switched by use of a spin transfer torque.
    Type: Grant
    Filed: December 23, 2008
    Date of Patent: July 10, 2012
    Assignees: Hitachi, Ltd., Tohoku University
    Inventors: Hideo Ohno, Shoji Ikeda, Jun Hayakawa
  • Patent number: 7894244
    Abstract: Provided is a high-speed, super-low-power-consumption nonvolatile memory with a high thermal stability. A nonvolatile magnetic memory is equipped with high-output tunnel magnetic resistance devices to each of which a free layer with a high thermal stability is applied, while a writing method by spin transfer torque is applied to the memory. The tunnel magnetic resistance device has a free layer including a first ferromagnetic film and the second ferromagnetic film each of which has a body center cubic structure and each of which contains Co, Fe and B. The free layer, additionally, includes a first non-magnetic layer. The tunnel magnetic resistance device has a layered structure formed of the free layer and a pinned layer with a MgO insulating film with a (100) orientation rock-salt structure interposed in between.
    Type: Grant
    Filed: April 25, 2007
    Date of Patent: February 22, 2011
    Assignees: Hitachi, Ltd., Tohoku University
    Inventors: Jun Hayakawa, Hideo Ohno, Shoji Ikeda, Young Min Lee
  • Patent number: 7838953
    Abstract: A magnetic memory cell and a magnetic random access memory that are highly reliable and low-power consuming. An upper electrode having a connecting area smaller than the area of a ferromagnetic free layer of a magnetic memory cell is connected to the ferromagnetic free layer. A current is applied to produce an uneven magnetic field over the magnetic memory cell, whereby spin-transfer torque magnetization reversal can be realized with low current and at small write error rate.
    Type: Grant
    Filed: October 4, 2007
    Date of Patent: November 23, 2010
    Assignee: Hitachi, Ltd.
    Inventors: Hideo Ohno, Shoji Ikeda, Jun Hayakawa
  • Patent number: 7759750
    Abstract: To provide a highly-reliable, low-power-consumption nonvolatile memory. A magnetization reversal of a ferromagnetic free layer is accomplished with a spin transfer torque in a state where an appropriate magnetic field is applied in a direction orthogonal to the direction of the magnetic easy axis of the ferromagnetic free layer of the tunnel magnetoresistance device that the magnetic memory cell includes. Preferably, the magnetic field is applied in a direction forming an angle of 45° with the direction perpendicular to the film plane.
    Type: Grant
    Filed: April 24, 2007
    Date of Patent: July 20, 2010
    Assignees: Hitachi, Ltd., Tohoku University
    Inventors: Jun Hayakawa, Hideo Ohno, Shoji Ikeda
  • Publication number: 20100034014
    Abstract: Provided is a high-speed and ultra-low-power-consumption nonvolatile memory having a high temperature stability at a zero magnetic field. In a tunnel magnetoresistive film constituting a nonvolatile magnetic memory that employs a writing method using a spin-transfer torque, an insulating layer and a nonmagnetic conductive layer are stacked above a ferromagnetic free layer.
    Type: Application
    Filed: August 5, 2008
    Publication date: February 11, 2010
    Inventors: Hideo Ohno, Shoji Ikeda, Young Min Lee, Jun Hayakawa
  • Publication number: 20090166773
    Abstract: Provided is a reliable nonvolatile memory with a lower power consumption. A ferromagnetic interconnection which is magnetized antiparallel or parallel to a magnetization direction of a ferromagnetic pinned layer in a giant magnetoresistive device or a tunnel magnetoresistive device constituting the magnetic memory cell, is connected to a ferromagnetic free layer with a non-magnetic layer being interposed in between, the ferromagnetic free layer serving as a recording layer. Thereby, the magnetization of the recording layer is switched by use of a spin transfer torque.
    Type: Application
    Filed: December 23, 2008
    Publication date: July 2, 2009
    Inventors: Hideo Ohno, Shoji Ikeda, Jun Hayakawa
  • Publication number: 20090096045
    Abstract: A fast and very low-power-consuming nonvolatile memory. A nonvolatile magnetic memory includes a high-output tunnel magnetoresistive device, in which spin-transfer torque is used for writing. A tunnel magnetoresistive device has a structure such that a ferromagnetic film of a body-centered cubic structure containing Co, Fe, and B, a MgO insulator film of a rock-salt structure oriented in (100), and a ferromagnetic film are stacked.
    Type: Application
    Filed: December 15, 2008
    Publication date: April 16, 2009
    Inventors: Jun HAYAKAWA, Hideo Ohno, Shoji Ikeda
  • Patent number: 7468542
    Abstract: A fast and very low-power-consuming nonvolatile memory. A nonvolatile magnetic memory includes a high-output tunnel magnetoresistive device, in which spin-transfer torque is used for writing. A tunnel magnetoresistive device has a structure such that a ferromagnetic film of a body-centered cubic structure containing Co, Fe, and B, a MgO insulator film of a rock-salt structure oriented in (100), and a ferromagnetic film are stacked.
    Type: Grant
    Filed: July 27, 2006
    Date of Patent: December 23, 2008
    Assignee: Hitachi, Ltd.
    Inventors: Jun Hayakawa, Hideo Ohno, Shoji Ikeda
  • Patent number: 7372666
    Abstract: A magnetic head according to the present invention includes a write magnetic pole on which a magnetic film has been formed, and is characterized by the magnetic film being formed by alternately laminating magnetic layers, which have iron (Fe) and cobalt (Co) as main components, and insulating layers, the insulating layers being formed as discontinuous films. With this construction, it is possible to form a write magnetic pole that has a high Bs value and high permeability, so that it is possible to provide a magnetic head that can record onto a high-density medium with a high coercive force.
    Type: Grant
    Filed: April 4, 2005
    Date of Patent: May 13, 2008
    Assignee: Fujitsu Limited
    Inventors: Shoji Ikeda, Takayuki Kubomiya, Masaaki Matsuoka
  • Publication number: 20080105938
    Abstract: A magnetic memory cell and a magnetic random access memory that are highly reliable and low-power consuming. An upper electrode having a connecting area smaller than the area of a ferromagnetic free layer of a magnetic memory cell is connected to the ferromagnetic free layer. A current is applied to produce an uneven magnetic field over the magnetic memory cell, whereby spin-transfer torque magnetization reversal can be realized with low current and at small write error rate.
    Type: Application
    Filed: October 4, 2007
    Publication date: May 8, 2008
    Inventors: Hideo Ohno, Shoji Ikeda, Jun Hayakawa
  • Publication number: 20080107922
    Abstract: The magnetic film includes an FeCo layer, restrains erasing data by a magnetic field leaked from a magnetic pole, has high saturation magnetic flux density and soft magnetism and writes data with high recording density. The magnetic film for a magnetic head of the present invention comprises: a nonmagnetic layer including at least one selected from a group of Ru, Rh, Ir, Cr, Cu, Au, Ag, Pt and Pd; a magnetic layer including Fe and Co. Anisotropy magnetic field is 0.8 kA/m or more.
    Type: Application
    Filed: October 9, 2007
    Publication date: May 8, 2008
    Inventors: Shoji Ikeda, Takayuki Kubomiya, Masaaki Matsuoka