Patents by Inventor Tomoo Yamamoto

Tomoo Yamamoto 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: 6846577
    Abstract: An ferromagnetic thin film is used to provide a magnetic recording medium whose noise is low and whose S/N value is high. The ferromagnetic thin film as the magnetic film of the magnetic recording medium is such that the fluctuation field of magnetic viscosity at 25° C. at the field strength equal to remanence coercivity or coercivity is not less than 15 oersteds and the coercivity is not less than 2000 oersteds.
    Type: Grant
    Filed: March 13, 2003
    Date of Patent: January 25, 2005
    Assignee: Hitachi, Ltd.
    Inventors: Kazusuke Yamanaka, Tomoo Yamamoto, Yuzuru Hosoe, Nobuyuki Inaba, Yasutaro Uesaka, Masaaki Futamoto, Yoshibumi Matsuda, Kenji Furusawa, Shinji Narishige
  • Publication number: 20040214049
    Abstract: A large-capacity, low-cost, longitudinal magnetic recording medium capable of ultra-high-density recording of 70 Gigabits or more per square inch is disclosed. The longitudinal magnetic recording medium of the present invention comprises a first seed layer, a second seed layer, a first underlayer, a second underlayer, and a magnetic layer, which are formed on a nonmagnetic substrate in this order. A material containing at least Al and any one of Ru and Re is used to form the second seed layer, and a material containing at least any one of Co and Ni and one or both of Al and Ti is used to form the first underlayer. It is also possible to use Cr or a Cr alloy containing Cr and at least one element selected from the constituent element group A consisting of Ti, Mo, and W for forming the second seed layer.
    Type: Application
    Filed: December 10, 2003
    Publication date: October 28, 2004
    Applicant: Hitachi Global Storage Technologies Japan, Ltd.
    Inventors: Tomoo Yamamoto, Yotsuo Yahisa, Tatsuya Hinoue, Hidekazu Kashiwase, Tetsuya Kanbe, Hiroyuki Suzuki
  • Patent number: 6706426
    Abstract: To obtain a large capacity magnetic recording medium capable of recording at a super high density of 3 Gbit or more per one square inch and a magnetic storage apparatus, a magnetic recording medium is prepared by disposing orientation control layers 31, 31′ having at least a B2 (CsCl) structure on a substrate 30, disposing a first underlayer comprising Cr and a second underlayer containing at least one element selected from Cr, Nb, Mo, Ta, W and Ti and having a lattice constant greater than that of the first underlayer and then forming a magnetic layer comprising Co as the main ingredient.
    Type: Grant
    Filed: March 10, 2000
    Date of Patent: March 16, 2004
    Assignee: Hitachi, Ltd.
    Inventors: Tomoo Yamamoto, Akira Ishikawa, Kazusuke Yamanaka, Atsushi Nakamura
  • Publication number: 20040043258
    Abstract: A large-capacity magnetic storage apparatus is disclosed, capable of performing ultra-high density magnetic recording of 50 gigabits or more per 1 square inch. In a perpendicular magnetic recording medium having a non-magnetic intermediate layer and a magnetic recording layer sequentially formed, the non-magnetic intermediate layer is composed of a layer having a face-centered cubic structure and containing a non-magnetic elements excluding Pt. Specifically, the intermediate layer mainly contains at least one selected from the group of elements constituted of Al, Cu, Rh, Pd, Ag, Ir and Au, and is composed of a film having a face-centered cubic (f. c. c.) structure. The magnetic recording layer contains at least Co, Cr and Pt, and is composed of a film having a hexagonal close-packed (h. c. p.) structure. More preferably, a non-magnetic h. c. p. intermediate layer is provided between the non-magnetic intermediate layer and the magnetic recording layer.
    Type: Application
    Filed: August 29, 2003
    Publication date: March 4, 2004
    Applicant: Hitachi, Ltd.
    Inventors: Tomoo Yamamoto, Ichiro Tamai, Akira Ishikawa
  • Publication number: 20030211364
    Abstract: A magnetic recording system includes an in-plane magnetic recording medium having a magnetic layer fabricated on a single underlayer or on a plurality of underlayers respectively fabricated on a substrate; a driver unit for driving the in-plane magnetic recording medium in a write direction; a magnetic head having a read unit and a write unit; a unit for moving the magnetic head relative to the in-plane magnetic recording medium; and a read/write signal processing unit for reading an output signal from the magnetic head and writing an input signal to the magnetic recording media, wherein the read unit of the magnetic head is a magnetoresistive head and the single underlayer or at least one of the plurality of underlayers is made of Co-containing amorphous material or fine crystal material, or is made of alloy material, the alloy material having as the main components at least one element selected from a group consisting of Cr, Mo, V and Ta and containing at least one element selected from a group consisting o
    Type: Application
    Filed: June 3, 2003
    Publication date: November 13, 2003
    Inventors: Tetsuya Kanbe, Akira Ishikawa, Ichiro Tamai, Yotsuo Yahisa, Yuzuru Hosoe, Kiwamu Tanahashi, Yoshibumi Matsuda, Hiroyuki Kataoka, Toshinori Ono, Shinji Fukaya, Kazuhiro Ura, Naoto Endo, Tomoo Yamamoto
  • Patent number: 6638648
    Abstract: A large-capacity magnetic storage apparatus is disclosed, capable of performing ultra-high density magnetic recording of 50 gigabits or more per 1 square inch. In a perpendicular magnetic recording medium having a non-magnetic intermediate layer and a magnetic recording layer sequentially formed, the non-magnetic intermediate layer is composed of a layer having a face-centered cubic structure and containing a non-magnetic elements excluding Pt. Specifically, the intermediate layer mainly contains at least one selected from the group of elements constituted of Al, Cu, Rh, Pd, Ag, Ir and Au, and is composed of a film having a face-centered cubic (f. c. c.) structure. The magnetic recording layer contains at least Co, Cr and Pt, and is composed of a film having a hexagonal close-packed (h. c. p.) structure. More preferably, a non-magnetic h. c. p. intermediate layer is provided between the non-magnetic intermediate layer and the magnetic recording layer.
    Type: Grant
    Filed: August 30, 2001
    Date of Patent: October 28, 2003
    Assignee: Hitachi, Ltd.
    Inventors: Tomoo Yamamoto, Ichiro Tamai, Akira Ishikawa
  • Patent number: 6627255
    Abstract: It is an object of the present invention to provide a magnetic recording medium which has a high level of magnetic antisotropy energy, retains stably the state of recording magnetization within the operating temperature range and is suitable for high-density recording with a low noise level, and a magnetic storage device for the magnetic recording medium. For attaining the above object, the magnetic recording film of the magnetic recording medium is characterized in that its magnetic anisotropy energy constant Ku at an absolute temperature of 300 K is greater than 3.6×106 erg/cc and the average particle diameter is larger than 5 nm and smaller than 12 nm.
    Type: Grant
    Filed: January 28, 2002
    Date of Patent: September 30, 2003
    Assignee: Hitachi, Ltd.
    Inventors: Nobuyuki Inaba, Tomoo Yamamoto, Teruaki Takeuchi, Masukazu Igarashi, Yoshio Takahashi
  • Publication number: 20030170497
    Abstract: An ferromagnetic thin film is used to provide a magnetic recording medium whose noise is low and whose S/N value is high. The ferromagnetic thin film as the magnetic film of the magnetic recording medium is such that the fluctuation field of magnetic viscosity at 25° C. at the field strength equal to remanence coercivity or coercivity is not less than 15 oersteds and the coercivity is not less than 2000 oersteds.
    Type: Application
    Filed: March 13, 2003
    Publication date: September 11, 2003
    Inventors: Kazusuke Yamanaka, Tomoo Yamamoto, Yuzuru Hosoe, Nobuyuki Inaba, Yasutaro Uesaka, Masaaki Futamoto, Yoshibumi Matsuda, Kenji Furusawa, Shinji Narishige
  • Patent number: 6613428
    Abstract: A thin film magnetic recording medium including a magnetic layer having a fluctuation field defined as S/Xirr, where S is magnetic viscosity and Xirr is irreversible susceptibility Xirr. The fluctuation field of the magnetic layer is not less than 15 oersteds.
    Type: Grant
    Filed: May 7, 2001
    Date of Patent: September 2, 2003
    Assignee: Hitachi, Ltd.
    Inventors: Kazusuke Yamanaka, Tomoo Yamamoto, Yuzuru Hosoe, Nobuyuki Inaba, Yasutaro Uesaka, Masaaki Futamoto, Yoshibumi Matsuda, Kenji Furusawa, Shinji Narishige
  • Patent number: 6605374
    Abstract: The present invention provides a magnetic recording medium having a magnetic layer deposited on a substrate through a single-layer underlayer or a multilayer-underlayer, the magnetic layer includes magnetic crystal grains having an acicular structure or amorphous magnetic particles, an average grain size of the magnetic grain and a grain-size dispersion normalized by the average grain size are less than 16 nm and less than 0.5, respectively, a value Ku·v/kT which results from dividing a product of a magnetic anisotropy constant Ku and a volume v of the magnetic grain by a product of a Boltzmann constant k and an absolute temperature T is selected to be greater than 60, and a film thickness of the magnetic layer falls within twice of the average grain size.
    Type: Grant
    Filed: May 3, 2002
    Date of Patent: August 12, 2003
    Assignee: Hitachi, Ltd.
    Inventors: Tetsuya Kanbe, Yoshio Takahashi, Akira Ishikawa, Ichiro Tamai, Yuzuru Hosoe, Yoshifumi Matsuda, Kiwamu Tanahashi, Tomoo Yamamoto
  • Patent number: 6596420
    Abstract: A magnetic recording system includes an in-plane magnetic recording medium having a magnetic layer fabricated on a single underlayer or on a plurality of underlayers respectively fabricated on a substrate; a driver unit for driving the in-plane magnetic recording medium in a write direction; a magnetic head having a read unit and a write unit; a unit for moving the magnetic head relative to the in-plane magnetic recording medium; and a read/write signal processing unit for reading an output signal from the magnetic head and writing an input signal to the magnetic recording media, wherein the read unit of the magnetic head is a magnetoresistive head and the single underlayer or at least one of the plurality of underlayers is made of Co-containing amorphous material or fine crystal material, or is made of alloy material, the alloy material having as the main components at least one element selected from a group consisting of Cr, Mo, V and Ta and containing at least one element selected from a group consisting o
    Type: Grant
    Filed: March 21, 2002
    Date of Patent: July 22, 2003
    Assignee: Hitachi, Ltd.
    Inventors: Tetsuya Kanbe, Akira Ishikawa, Ichiro Tamai, Yotsuo Yahisa, Yuzuru Hosoe, Kiwamu Tanahashi, Yoshibumi Matsuda, Hiroyuki Kataoka, Toshinori Ono, Shinji Fukaya, Kazuhiro Ura, Naoto Endo, Tomoo Yamamoto
  • Patent number: 6544672
    Abstract: Disclosed is a magnetic recording medium capable of reducing noise and an error rate of the medium. The medium comprises a nonmagnetic substrate; a magnetic layer formed on the surface of the nonmagnetic substrate directly or through a nonmagnetic underlayer; and a protective layer formed on the magnetic layer; wherein the magnetic recording medium satisfies the following relationships: −0.5≦{Hc(1)−Hc(p)}/Hc(1)≦0.3 Hc(1)≧2 kOe 20 G×&mgr;m≦Br(1)×t≦100 G×&mgr;m where Hc(1) indicates a corecivity of the magnetic layer measured in the longitudinal direction; Hc(p) indicates a coercivity of the magnetic layer measured in the perpendicular direction; Br(1) indicates a remanent magnetization of the magnetic layer measured in the longitudinal direction; and “t” indicates a layer thickness of the magnetic layer.
    Type: Grant
    Filed: October 3, 2000
    Date of Patent: April 8, 2003
    Assignee: Hitachi, Ltd.
    Inventors: Masaaki Futamoto, Nobuyuki Inaba, Tomoo Yamamoto, Masukazu Igarashi, Yuzuru Hosoe, Akira Ishikawa
  • Publication number: 20020168547
    Abstract: The present invention provides a magnetic recording medium having a magnetic layer deposited on a substrate through a single-layer underlayer or a multilayer-underlayer, the magnetic layer includes magnetic crystal grains having an acicular structure or amorphous magnetic particles, an average grain size of the magnetic grain and a grain-size dispersion normalized by the average grain size are less than 16 nm and less than 0.5, respectively, a value Ku·v/kT which results from dividing a product of a magnetic anisotropy constant Ku and a volume v of the magnetic grain by a product of a Boltzmann constant k and an absolute temperature T is selected to be greater than 60, and a film thickness of the magnetic layer falls within twice of the average grain size.
    Type: Application
    Filed: May 3, 2002
    Publication date: November 14, 2002
    Applicant: Hitachi, Ltd.
    Inventors: Tetsuya Kanbe, Yoshio Takahashi, Akira Ishikawa, Ichiro Tamai, Yuzuru Hosoe, Yoshifumi Matsuda, Kiwamu Tanahashi, Tomoo Yamamoto
  • Publication number: 20020150796
    Abstract: A magnetic recording system includes an in-plane magnetic recording medium having a magnetic layer fabricated on a single underlayer or on a plurality of underlayers respectively fabricated on a substrate; a driver unit for driving the in-plane magnetic recording medium in a write direction; a magnetic head having a read unit and a write unit; a unit for moving the magnetic head relative to the in-plane magnetic recording medium; and a read/write signal processing unit for reading an output signal from the magnetic head and writing an input signal to the magnetic recording media, wherein the read unit of the magnetic head is a magnetoresistive head and the single underlayer or at least one of the plurality of underlayers is made of Co-containing amorphous material or fine crystal material, or is made of alloy material, the alloy material having as the main components at least one element selected from a group consisting of Cr, Mo, V and Ta and containing at least one element selected from a group consisting o
    Type: Application
    Filed: March 21, 2002
    Publication date: October 17, 2002
    Inventors: Tetsuya Kanbe, Akira Ishikawa, Ichiro Tamai, Yotsuo Yahisa, Yuzuru Hosoe, Kiwamu Tanahashi, Yoshibumi Matsuda, Hiroyuki Kataoka, Toshinori Ono, Shinji Fukaya, Kazuhiro Ura, Naoto Endo, Tomoo Yamamoto
  • Publication number: 20020146592
    Abstract: Disclosed is a magnetic recording medium capable of reducing noise and an error rate of the medium.
    Type: Application
    Filed: March 26, 2002
    Publication date: October 10, 2002
    Inventors: Masaaki Futamoto, Nobuyuki Inaba, Tomoo Yamamoto, Masukazu Igarashi, Yuzuru Hosoe, Akira Ishikawa
  • Patent number: 6403242
    Abstract: The present invention provides a magnetic recording medium having a magnetic layer deposited on a substrate through a single-layer underlayer or a multilayer-underlayer, the magnetic layer includes magnetic crystal grains having an acicular structure or amorphous magnetic particles, an average grain size of the magnetic grain and a grain-size dispersion normalized by the average grain size are less than 16 nm and less than 0.5, respectively, a value Ku·v/kT which results from dividing a product of a magnetic anisotropy constant Ku and a volume v of the magnetic grain by a product of a Boltzmann constant k and an absolute temperature T is selected to be greater than 60, and a film thickness of the magnetic layer falls within twice of the average grain size.
    Type: Grant
    Filed: March 14, 2000
    Date of Patent: June 11, 2002
    Assignee: Hitachi, Ltd.
    Inventors: Tetsuya Kanbe, Yoshio Takahashi, Akira Ishikawa, Ichiro Tamai, Yuzuru Hosoe, Yoshifumi Matsuda, Kiwamu Tanahashi, Tomoo Yamamoto
  • Patent number: 6403240
    Abstract: A magnetic recording system includes an in-plane magnetic recording medium having a magnetic layer fabricated on a single underlayer or on a plurality of underlayers respectively fabricated on a substrate; a driver unit for driving the in-plane magnetic recording medium in a write direction; a magnetic head having a read unit and a write unit; a unit for moving the magnetic head relative to the in-plane magnetic recording medium; and a read/write signal processing unit for reading an output signal from the magnetic head and writing an input signal to the magnetic recording media, wherein the read unit of the magnetic head is a magnetoresistive head and the single underlayer or at least one of the plurality of underlayers is made of Co-containing amorphous material or fine crystal material, or is made of alloy material, the alloy material having as the main components at least one element selected from a group consisting of Cr, Mo, V and Ta and containing at least one element selected from a group consisting o
    Type: Grant
    Filed: May 19, 1997
    Date of Patent: June 11, 2002
    Assignee: Hitachi, Ltd.
    Inventors: Tetsuya Kanbe, Akira Ishikawa, Ichiro Tamai, Yotsuo Yahisa, Yuzuru Hosoe, Kiwamu Tanahashi, Yoshibumi Matsuda, Hiroyuki Kataoka, Toshinori Ono, Shinji Fukaya, Kazuhiro Ura, Naoto Endo, Tomoo Yamamoto
  • Publication number: 20020068200
    Abstract: It is an object of the present invention to provide a magnetic recording medium which has a high level of magnetic anisotropy energy, retains stably the state of recording magnetization within the operating temperature range and is suitable for high-density recording with a low noise level, and a magnetic storage device for the magnetic recording medium.
    Type: Application
    Filed: January 28, 2002
    Publication date: June 6, 2002
    Applicant: Hitachi, Ltd.
    Inventors: Nobuyuki Inaba, Tomoo Yamamoto, Teruaki Takeuchi, Masukazu Igarashi, Yoshio Takahashi
  • Publication number: 20020058161
    Abstract: A large-capacity magnetic storage apparatus is disclosed, capable of performing ultra-high density magnetic recording of 50 gigabits or more per 1 square inch. In a perpendicular magnetic recording medium having a non-magnetic intermediate layer and a magnetic recording layer sequentially formed, the non-magnetic intermediate layer is composed of a layer having a face-centered cubic structure and containing a non-magnetic elements excluding Pt. Specifically, the intermediate layer mainly contains at least one selected from the group of elements constituted of Al, Cu, Rh, Pd, Ag, Ir and Au, and is composed of a film having a face-centered cubic (f. c. c.) structure. The magnetic recording layer contains at least Co, Cr and Pt, and is composed of a film having a hexagonal close-packed (h. c. p.) structure. More preferably, a non-magnetic h. c. p. intermediate layer is provided between the non-magnetic intermediate layer and the magnetic recording layer.
    Type: Application
    Filed: August 30, 2001
    Publication date: May 16, 2002
    Applicant: Hitachi, Ltd.
    Inventors: Tomoo Yamamoto, Ichiro Tamai, Akira Ishikawa
  • Patent number: 6365287
    Abstract: It is an object of the present invention to provide a magnetic recording medium which has a high level of magnetic anisotropy energy, retains stably the state of recording magnetization within the operating temperature range and is suitable for high-density recording with a low noise level, and a magnetic storage device for the magnetic recording medium. For attaining the above object, the magnetic recording film of the magnetic recording medium is characterized in that its magnetic anisotropy energy constant Ku at an absolute temperature of 300 K is greater than 3.6×106 erg/cc and the average particle diameter is larger than 5 nm and smaller than 12 nm.
    Type: Grant
    Filed: January 19, 2000
    Date of Patent: April 2, 2002
    Assignee: Hitachi, Ltd.
    Inventors: Nobuyuki Inaba, Tomoo Yamamoto, Teruaki Takeuchi, Masukazu Igarashi, Yoshio Takahashi