Patents by Inventor Keiichi Nagasaka

Keiichi Nagasaka 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: 20120113542
    Abstract: The present invention provides a magnetic recording head and a magnetic recording device that realize information transfer speed exceeding 1 Gbit/s in microwave assisted magnetic recording applied to a magnetic recording device having recording density exceeding 1 Tbit/in2. Concerning a reference layer that supplies spin torque to a high-speed magnetization rotator serving as a microwave field generation source, when an externally applied field to the reference layer is represented as Hext, a magnetic anisotropy field of the reference layer is represented as Hk, and an effective demagnetizing field in a vertical direction of a film surface of the reference layer is represented as Hd-eff, the fixing layer is configured to satisfy conditions Hext?Hk+Hd-eff>0 and Hext+Hk?Hd-eff>0.
    Type: Application
    Filed: November 2, 2011
    Publication date: May 10, 2012
    Inventors: Masukazu Igarashi, Yo Sato, Masato Shiimoto, Keiichi Nagasaka
  • Publication number: 20120069465
    Abstract: The present invention provides a spin torque oscillator that can realize stable oscillation and has high reliability. A laminated structure including a first magnetic layer 1 having a bcc crystal structure and having in-plane magnetic anisotropy and a second magnetic layer 2 having perpendicular magnetic anisotropy laminated on the first magnetic layer 1 and including a multilayer film of Co and Ni is used.
    Type: Application
    Filed: August 12, 2011
    Publication date: March 22, 2012
    Applicant: HITACHI, LTD.
    Inventors: Yo SATO, Keiichi NAGASAKA, Masato SHIIMOTO, Masato MATSUBARA
  • Publication number: 20100061135
    Abstract: A magnetic wire unit for storing information thereon includes a magnetic wire containing a material having an axis of easy magnetization, and extending in a first direction, the axis being switchable between the first direction and the second direction perpendicular to the first direction, the magnetic wire being capable of holding a plurality of magnetic domains representing information. The magnetic wire unit includes a current supply unit for applying an electric current to the magnetic wire so as to move magnetic domain walls defining the magnetic domains in the magnetic wire.
    Type: Application
    Filed: August 6, 2009
    Publication date: March 11, 2010
    Applicant: FUJITSU LIMITED
    Inventors: Keiichi Nagasaka, Hiroshi Ashida, Takao Ochiai, Ken Tamanoi
  • Publication number: 20100054033
    Abstract: A magnetic thin line includes a first magnetic film having in-plane magnetic anisotropy and a second magnetic film that is magnetically coupled to the first magnetic film and has perpendicular magnetic anisotropy. With the coupling of the first magnetic film and the second magnetic film, magnetic wall width of the first magnetic film is lower than a case where the first magnetic film is not magnetically coupled to the second magnetic film.
    Type: Application
    Filed: August 19, 2009
    Publication date: March 4, 2010
    Applicant: FUJITSU LIMITED
    Inventors: Takao Ochiai, Hiroshi Ashida, Keiichi Nagasaka
  • Publication number: 20100053794
    Abstract: In a thermally assisted magnetic recording method, tunneling current is applied from a tunneling current wiring arranged on a magnetic recording head configured to fly above a magnetic recording medium having a bit pattern formed of recording bits separated from one another by an insulator to a desired recording bit of the magnetic recording medium, so that the recording bit is heated and thus coercivity of the recording bit is reduced. Then, an alternating magnetic field corresponding to information to be recorded is applied from the magnetic recording head to the heated recording bit, so that the information can be recorded in the magnetic recording medium.
    Type: Application
    Filed: July 7, 2009
    Publication date: March 4, 2010
    Applicant: FUJITSU LIMITED
    Inventors: Hideki Mashima, Keiichi Nagasaka
  • Publication number: 20090323406
    Abstract: A magnetic memory element includes an impurity element, and magnetic thin lines to which the impurity element is added to adjust the movement of a magnetic domain wall in a magnetic field. Applying a voltage to the magnetic thin lines controls a position of the magnetic domain wall to invert a magnetization direction of a magnetic recording layer adjacent to the magnetic domain wall, by which information is recorded.
    Type: Application
    Filed: March 16, 2009
    Publication date: December 31, 2009
    Applicant: FUJITSU LIMITED
    Inventors: Takao Ochiai, Hiroshi Ashida, Keiichi Nagasaka
  • Patent number: 7538987
    Abstract: A CPP spin-valve element formed on a substrate including a free layer structure including at least one ferromagnetic layer and a pinned layer structure including at least one ferromagnetic layer. The free layer is magnetically softer than the pinned layer. A thin non-magnetic spacer layer structure configured to separate the free layer and the pinned layer is provided in order to prevent a magnetic coupling between the free and pinned layer structures, and to allow an electric current to go there through. At least two current-confining (CC) layer structures including at least two parts having significantly different current conductivities are incorporated therein.
    Type: Grant
    Filed: July 3, 2003
    Date of Patent: May 26, 2009
    Assignees: University of Alabama, Fujitsu, Ltd.
    Inventors: Hideo Fujiwara, Keiichi Nagasaka, Tong Zhao, William H. Butler, Julian Velev, Amrit Bandyopadhyay
  • Patent number: 7450351
    Abstract: A magnetoresistive element of a CPP type configuration including a fixed magnetic layer, a first non-magnetic layer, a free magnetic layer, and a second non-magnetic layer is disclosed. The magnetoresistive element includes a first interface layer situated between the free magnetic layer and the first non-magnetic layer, and a second interface layer situated between the free magnetic layer and the second non-magnetic layer. The first interface layer and the second interface layer include a material mainly having CoNiFe.
    Type: Grant
    Filed: June 20, 2005
    Date of Patent: November 11, 2008
    Assignee: Fujitsu Limited
    Inventors: Hirotaka Oshima, Keiichi Nagasaka, Arata Jogo, Yutaka Shimizu, Atsushi Tanaka
  • Patent number: 7433160
    Abstract: A magnetoresistive element is disclosed that includes a magnetoresistive film; a cap film configured to cover the magnetoresistive film and include a three-layer structure in at least a part thereof, the three-layer structure being formed of a third protection layer, a second protection layer, and a first protection layer in order from the magnetoresistive film side; and upper and lower terminals for applying a sense current perpendicularly to the surface of the magnetoresistive film. The magnetoresistive film includes a first magnetic layer whose direction of magnetization is changed by an external magnetic field, a second magnetic layer whose direction of magnetization is fixed with respect to the external magnetic field, and a nonmagnetic layer magnetically separating the first magnetic layer and the second magnetic layer.
    Type: Grant
    Filed: July 26, 2005
    Date of Patent: October 7, 2008
    Assignee: Fujitsu Limited
    Inventors: Keiichi Nagasaka, Yutaka Shimizu
  • Patent number: 7428127
    Abstract: A CPP magnetoresistive effect element includes a free magnetization layer, a fixed magnetization layer, and a plurality of conductive non-magnetic intermediate layers formed between the free magnetization layer and the fixed magnetization layer. An insulating layer and a magnetic layer including magnetic atoms are provided between any two of the non-magnetic intermediate layers.
    Type: Grant
    Filed: January 25, 2005
    Date of Patent: September 23, 2008
    Assignee: Fujitsu Limited
    Inventors: Keiichi Nagasaka, Yoshihiko Seyama, Hirotaka Oshima, Yutaka Shimizu, Atsushi Tanaka
  • Publication number: 20080080097
    Abstract: A magnetoresistive element is disclosed that includes first and second terminals provided on first and second opposing surfaces, respectively, of a magnetoresistive film; the magnetoresistive film including a fixed magnetization layer, a non-magnetic metal layer, and a free magnetization layer stacked in this order from the first terminal side; and a first magnetic coupling interruption layer covering the free magnetization layer and a second magnetic coupling interruption layer covering the first magnetic coupling interruption layer provided between the magnetoresistive element and the second terminal. The first magnetic coupling interruption layer includes a first non-magnetic material causing spin-dependent interface scattering.
    Type: Application
    Filed: September 6, 2007
    Publication date: April 3, 2008
    Applicant: FUJITSU LIMITED
    Inventor: Keiichi NAGASAKA
  • Patent number: 7342751
    Abstract: The magnetoresistive effect element comprises an electrode layer 12 of a crystalline material; a base layer 14 of a conductive amorphous material formed over the electrode layer 12, an antiferromagnetic layer 18 of a crystalline material formed over the base layer 14, a ferromagnetic layer 20 formed over the antiferromagnetic layer 18 and having the magnetization direction defined by the antiferromagnetic layer 18, a nonmagnetic intermediate layer 22 formed over the ferromagnetic layer 20, a ferromagnetic layer 24 formed over the nonmagnetic intermediate layer 22 and having the magnetization direction changed by an external magnetic field, and an electrode layer 28 formed over the ferromagnetic layer 24.
    Type: Grant
    Filed: March 3, 2005
    Date of Patent: March 11, 2008
    Assignee: Fujitsu Limited
    Inventors: Keiichi Nagasaka, Yutaka Shimizu, Atsushi Tanaka
  • Publication number: 20070217083
    Abstract: A spin valve film has a lamination structure of a pinned layer, a non-magnetic intermediate layer and a free layer. The pinned layer is made of ferromagnetic material and has a fixed magnetization direction. The non-magnetic intermediate layer is made of non-magnetic conductive material. The free layer is made of ferromagnetic material and changes a magnetization direction by external magnetic field. Electrodes let current flow through the spin valve film in a lamination direction. At least one of the pinned layer and the free layer includes a lamination portion of a first layer and a second layer stacked alternately. The first layer has a composition ratio of elements presenting ferromagnetism higher than that in the second layer. The second layer has a composition ratio of elements presenting non-magnetism higher than that in the first layer. The lamination portion includes at least two first layers and at least one second layer.
    Type: Application
    Filed: July 11, 2006
    Publication date: September 20, 2007
    Applicant: FUJITSU LIMITED
    Inventors: Keiichi Nagasaka, Hirotaka Oshima, Arata Jogo, Yutaka Shimizu
  • Publication number: 20070048485
    Abstract: A magnetoresistive effect element of a CPP type includes a fixed magnetization layer, a non-magnetic layer and a free magnetization layer formed of CoFeAl. The CoFeAl has a composition falling within a range defined by straight lines connecting points A, B, C, D, E, F and A, in that order, in a ternary composition diagram. The point A is (55, 10, 35), the point B is (50, 15, 35), the point C is (50, 20, 30), the point D is (55, 25, 20), the point E is (60, 25, 15), and the point F is (70, 15, 15), where coordinates of the composition of each point is represented by (Co content, Fe content, Al content). Each content is expressed by atomic percent.
    Type: Application
    Filed: May 22, 2006
    Publication date: March 1, 2007
    Applicant: FUJITSU LIMITED
    Inventors: Arata Jogo, Hirotaka Oshima, Keiichi Nagasaka
  • Patent number: 7180713
    Abstract: A magnetoresistive element that detects a change of magnetoresistance by giving a sense current in the thickness direction of a magnetoresistive effect film including at least a base layer, a free layer, a non-magnetic layer, a pinned layer, a pinning layer, and a protection layer, includes a granular structure layer that includes conductive particles and an insulating matrix material in the form of a thin film containing the conductive particles in a dispersed state and having a smaller thickness than the particle diameter of the conductive particles, the granular structure layer being interposed between at least two adjacent layers among the base layer, the free layer, the non-magnetic layer, the pinned layer, the pinning layer, and the protection layer.
    Type: Grant
    Filed: October 16, 2002
    Date of Patent: February 20, 2007
    Assignee: Fujitsu Limited
    Inventors: Keiichi Nagasaka, Yoshihiko Seyama, Takahiko Sugawara, Yutaka Shimizu, Atsushi Tanaka
  • Patent number: 7116528
    Abstract: A smaller electrode layer of an upper electrode is formed on a surface of a free magnetic layer. A domain controlling film of an insulating material is formed adjacent to the smaller electrode layer on the surface of the free magnetic layer. Magnetization of the free magnetic layer is oriented in a single direction based on magnetic exchange coupling between the domain controlling film and the free magnetic layer. An electric connection is established between the free magnetic layer and the upper electrode only through the smaller electrode layer. The path of a sensing current can be reduced in the free and a pinned magnetic layer. A higher sensitivity can thus be obtained in the CPP structure magnetoresistive element. Effective magnetic core width can also be reduced in the CPP structure magnetoresistive element.
    Type: Grant
    Filed: July 22, 2003
    Date of Patent: October 3, 2006
    Assignee: Fujitsu Limited
    Inventors: Keiichi Nagasaka, Yutaka Shimizu
  • Patent number: 7116533
    Abstract: A magnetoresistive sensor including the following layers, in order: a first conductor layer; a first antiferromagnetic layer; a first pinned ferromagnetic layer; a first nonmagnetic intermediate layer; a free ferromagnetic layer; a second nonmagnetic intermediate layer; a second pinned ferromagnetic layer; a second antiferromagnetic layer; and a second conductor layer. Alternatively, the magnetoresistive sensor may include the following layers, in order: a first conductor layer; a first free ferromagnetic layer; a first nonmagnetic intermediate layer; a first pinned ferromagnetic layer; an antiferromagnetic layer; a second pinned ferromagnetic layer; a second nonmagnetic intermediate layer; a second free ferromagnetic layer; and a second conductor layer.
    Type: Grant
    Filed: January 6, 2006
    Date of Patent: October 3, 2006
    Assignee: Fujitsu Limited
    Inventors: Yoshihiko Seyama, Atsushi Tanaka, Keiichi Nagasaka, Yutaka Shimizu, Shin Eguchi, Hitoshi Kanai, Reiko Kondo, Hitoshi Kishi, Junya Ikeda
  • Publication number: 20060209473
    Abstract: A magnetoresistive element of a CPP type configuration including a fixed magnetic layer, a first non-magnetic layer, a free magnetic layer, and a second non-magnetic layer is disclosed. The magnetoresistive element includes a first interface layer situated between the free magnetic layer and the first non-magnetic layer, and a second interface layer situated between the free magnetic layer and the second non-magnetic layer. The first interface layer and the second interface layer include a material mainly having CoNiFe.
    Type: Application
    Filed: June 20, 2005
    Publication date: September 21, 2006
    Inventors: Hirotaka Oshima, Keiichi Nagasaka, Arata Jogo, Yutaka Shimizu, Atsushi Tanaka
  • Publication number: 20060209471
    Abstract: A magnetoresistive element is disclosed that includes a magnetoresistive film; a cap film configured to cover the magnetoresistive film and include a three-layer structure in at least a part thereof, the three-layer structure being formed of a third protection layer, a second protection layer, and a first protection layer in order from the magnetoresistive film side; and upper and lower terminals for applying a sense current perpendicularly to the surface of the magnetoresistive film. The magnetoresistive film includes a first magnetic layer whose direction of magnetization is changed by an external magnetic field, a second magnetic layer whose direction of magnetization is fixed with respect to the external magnetic field, and a nonmagnetic layer magnetically separating the first magnetic layer and the second magnetic layer.
    Type: Application
    Filed: July 26, 2005
    Publication date: September 21, 2006
    Applicant: FUJITSU LIMITED
    Inventors: Keiichi Nagasaka, Yutaka Shimizu
  • Publication number: 20060119989
    Abstract: Disclosed herein is a spin valve magnetoresistive sensor including a first conductor layer, a free ferromagnetic layer provided on the first conductor layer, a nonmagnetic intermediate layer provided on the free ferromagnetic layer, a pinned ferromagnetic layer provided on the nonmagnetic intermediate layer, an antiferromagnetic layer provided on the pinned ferromagnetic layer, and a second conductor layer provided on the antiferromagnetic layer. At least one of the free ferromagnetic layer and the pinned ferromagnetic layer has a thickness larger than that providing a maximum resistance change rate or resistance change amount in the case of passing a current in an in-plane direction of the at least one layer. That is, the thickness of at least one of the free ferromagnetic layer and the pinned ferromagnetic layer falls in the range of 3 nm to 12 nm.
    Type: Application
    Filed: January 6, 2006
    Publication date: June 8, 2006
    Inventors: Yoshihiko Seyama, Atsushi Tanaka, Keiichi Nagasaka, Yutaka Shimizu, Shin Eguchi, Hitoshi Kanai, Reiko Kondo, Hitoshi Kishi, Junya Ikeda