Patents by Inventor Takao Imagawa

Takao Imagawa 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: 20020041473
    Abstract: An oxide layer and an antiparallel coupling layer are inserted into a ferromagnetic pinned layer to be subjected to heat treatment with appropriate ferromagnetic film thickness and magnetization field to form a spin-valve film, which is controlled in amount of magnetization and is high in magnetoresistance.
    Type: Application
    Filed: October 5, 2001
    Publication date: April 11, 2002
    Inventors: Hiroyuki Hoshiya, Kenichi Meguro, Takao Imagawa
  • Patent number: 6319622
    Abstract: Magnetoresistive and spin valve heads have a layered structure. Common to each of the layered structures of these heads is the combination of a soft-magnetic layer of essentially NiFe near a spacer layer of essentially Ta, which is used for insuring (111) crystal orientation of the NiFe layer. An isolate layer is interposed between the spacer layer and the soft-magnetic layer to prevent a diffusion boundary from being created at the interface of these layers which tends to degrade the soft-magnetic property of the NiFe layer, especially when the thickness of the soft-magnetic layer is 10 and nm or less.
    Type: Grant
    Filed: August 4, 2000
    Date of Patent: November 20, 2001
    Assignee: Hitachi, Ltd.
    Inventors: Satoshi Shigematsu, Takao Imagawa, Koichi Nishioka, Hiroshi Kamio, Katsuhisa Usami
  • Patent number: 6275360
    Abstract: A read-write head is capable of suppressing fluctuation on a reproduced waveform caused by repetition of a writing and reading operation, and is capable suppressing noise appearing in the reproduced waveform just after a writing operation is carried out. The read-write head has an upper magnetic core, an upper shield also serving as an lower magnetic core, a lower shield and a magnetoresistive film arranged between the upper shield and the lower shield. The upper shield has a soft magnetic film having a magnitude of anisotropy field of 5 to 30 Oe, or is a multilayer film composed of a high saturation magnetic flux density film and a negative magneto-striction film. The lower shield has a soft magnetic film having a magnitude of anisotropy field of 5 to 30 Oe.
    Type: Grant
    Filed: September 24, 1998
    Date of Patent: August 14, 2001
    Assignee: Hitachi, Ltd.
    Inventors: Kazuhiro Nakamoto, Takashi Kawabe, Tetsuo Kobayashi, Shun-ichi Marumi, Shinji Narishige, Takao Imagawa
  • Patent number: 6172859
    Abstract: A magnetoresistive head in which Barkhausen noise is substantially suppressed and a variation in reproduction is minimized, and a magnetic disk apparatus using the same magnetic head have been provided. The feature of the magnetic head and the magnetic disk apparatus of the invention resides in the provision of the longitudinal bias layer which comprises a hard magnetic thin film formed on an underlayer made of either of a ferromagnetic thin film having a body-centered cubic lattice crystal structure formed of body-centered cells, an amorphous ferromagnetic thin film or antiferromagnetic thin film having a body-centered cubic lattice crystal structure formed of body-centered cells.
    Type: Grant
    Filed: July 22, 1996
    Date of Patent: January 9, 2001
    Assignee: Hitachi, Ltd.
    Inventors: Katsuro Watanabe, Takashi Kawabe, Shigeru Tadokoro, Hiroshi Kamio, Takao Imagawa
  • Patent number: 6157526
    Abstract: A magnetoresistive head in which Barkhausen noise is substantially suppressed and a variation in reproduction is minimized, and a magnetic disk apparatus using the same magnetic head have been provided. The feature of the magnetic head and the magnetic disk apparatus of the invention resides in the provision of a longitudinal bias layer which comprises a hard magnetic thin film formed on an underlayer made of either a ferromagnetic thin film having a body-centered cubic lattice crystal structure, or an amorphous ferromagnetic thin film or antiferromagnetic thin film having a body-centered cubic lattice crystal structure.
    Type: Grant
    Filed: November 30, 1999
    Date of Patent: December 5, 2000
    Assignee: Hitachi, Ltd.
    Inventors: Katsuro Watanabe, Takashi Kawabe, Shigeru Tadokoro, Hiroshi Kamio, Takao Imagawa
  • Patent number: 6120919
    Abstract: Magnetoresistive and spin valve heads have a layered structure. Common to each of the layered structures of these heads is the combination of a soft-magnetic layer of essentially NiFe near a spacer layer of essentially Ta, which is used for insuring (111) crystal orientation of the NiFe layer. An isolate layer is interposed between the spacer layer and the soft-magnetic layer to prevent a diffusion boundary from being created at the interface of these layers which tends to degrade the soft-magnetic property of the NiFe layer, especially when the thickness of the soft-magnetic layer is 10 and nm or less.
    Type: Grant
    Filed: July 14, 1998
    Date of Patent: September 19, 2000
    Assignee: Hitachi, Ltd.
    Inventors: Satoshi Shigematsu, Takao Imagawa, Koichi Nishioka, Hiroshi Kamio, Katsuhisa Usami
  • Patent number: 6088196
    Abstract: A magnetoresistive head comprising a magnetoresistive film having electric resistance varying with a magnetic field, a pair of electrodes for causing a current to flow into the magnetoresistive film, and a soft magnetic film for applying a transverse biasing field to the magnetoresistive film, the soft magnetic film containing at least one material of iron, cobalt, and nickel, and at least one compound of zirconium oxide, aluminum oxide, hafnium oxide, titanium oxide, beryllium oxide, magnesium oxide, a rare earth oxygen compound, zirconium nitride, hafnium nitride, aluminum nitride, titanium nitride, beryllium nitride, magnesium nitride, silicon nitride, and a rare earth nitrogen compound. The electric resistance of the soft magnetic film is raised by adding a compound thereto and current diverted from the magnetoresistive film to the soft magnetic film decreases, so that the reproducing voltage of the magnetoresistive head rises.
    Type: Grant
    Filed: July 7, 1997
    Date of Patent: July 11, 2000
    Assignee: Hitachi, Ltd.
    Inventors: Shigeru Tadokoro, Katsuro Watanabe, Takao Imagawa, Yasunari Tajima
  • Patent number: 5995338
    Abstract: A magnetoresistive head in which Barkhausen noise is substantially suppressed and a variation in reproduction is minimized, and a magnetic disk apparatus using the same magnetic head have been provided. The feature of the magnetic head and the magnetic disk apparatus of the invention resides in the provision of a longitudinal bias layer which comprises a hard magnetic thin film formed on an underlayer made of either a ferromagnetic thin film having a body-centered cubic lattice crystal structure, or an amorphous ferromagnetic thin film or antiferromagnetic thin film having a body-centered cubic lattice crystal structure.
    Type: Grant
    Filed: October 23, 1996
    Date of Patent: November 30, 1999
    Assignee: Hitachi, Ltd.
    Inventors: Katsuro Watanabe, Takashi Kawabe, Shigeru Tadokoro, Hiroshi Kamio, Takao Imagawa
  • Patent number: 5969910
    Abstract: A magnetic head having a magnetoresistive head having a spin valve structure in which a composite magnetic layer of a rotatable magnetizing direction layer and oxide or the like is used for a lower shielding layer and/or an upper shielding layer and a magnetic disk apparatus using such a head are disclosed. According to the invention, a magnetic head having a head of a magnetoresistance effect type generating a high output with low noises and a magnetic disk apparatus having a large quantity with high recording density can be realized.
    Type: Grant
    Filed: May 19, 1997
    Date of Patent: October 19, 1999
    Assignee: Hitachi, Ltd.
    Inventors: Takao Imagawa, Shigeru Tadokoro, Yasunari Tajima, Hiroshi Kamio
  • Patent number: 5872690
    Abstract: A magnetic laminated film used for a magnetic transducer is constructed in such a way that a ferromagnetic film as a ferromagnetic body is made of, for example, a Ni--Fe alloy film, formed on a substrate made of, for example, glass, and an antiferromagnetic film as an antiferromagnetic body having crystal structure of body-centered cubic lattice, for example, made of a Cr alloy film is laminated on the top layer. Further, a magnetic transducer using the magnetic laminated film is applied to a magnetic head in a magnetic recording device in accordance with the present invention.
    Type: Grant
    Filed: July 11, 1997
    Date of Patent: February 16, 1999
    Assignee: Hitachi, Ltd.
    Inventors: Shigeru Tadokoro, Takao Imagawa, Katsuro Watanabe, Akira Kumagai
  • Patent number: 5726838
    Abstract: A magnetic disc apparatus capable of noiseless, high-output reproduction is disclosed. A magnetic head including a magnetic domain control structure having an antiferromagnetic film for applying a longitudinally biasing magnetic field to a magneto-sensitive portion of a magneto-resistance effect film, and a magnetic film smaller in spontaneous magnetization than the magneto-resistance effect film, which magnetic film is interposed between the magneto-resistance effect film and the antiferromagnetic film. A magnetic disc apparatus is thus realized which is high in recording density and usable in stable manner within the operating temperature range.
    Type: Grant
    Filed: March 7, 1995
    Date of Patent: March 10, 1998
    Assignee: Hitachi, Ltd.
    Inventors: Susumu Soeya, Shigeru Tadokoro, Takao Imagawa, Akira Kumagai, Moriaki Fuyama, Shinji Narishige
  • Patent number: 5668685
    Abstract: A magnetic disc apparatus is disclosed, in which a magneto-resistance effect film converts a magnetic signal into an electrical signal by use of the magneto-resistance effect, a pair of electrodes supplies a signal detection current to the magneto-resistance effect film, and a magnetic domain control layer controls the magnetic domain of the magneto-resistance effect film. The magneto-resistance effect film, the electrodes and the magnetic domain control layer constitute a magnetic head of magneto-resistance effect type. An isolation film is formed in a magneto-sensitive portion of the magneto-resistance effect film between the magneto-resistance effect film and the magnetic domain control layer to break the magnetic coupling between the magneto-resistance effect film and the magnetic domain control layer.
    Type: Grant
    Filed: December 7, 1994
    Date of Patent: September 16, 1997
    Assignee: Hitachi, Ltd.
    Inventors: Susumu Soeya, Shigeru Tadokoro, Takao Imagawa, Eiji Ashida, Moriaki Fuyama, Hiroshi Fukui, Saburo Suzuki, Masayuki Takagi, Shinji Narishige
  • Patent number: 5436777
    Abstract: A magnetoresistive head has a substrate (1) and, on the substrate, a magnetoresistive film (40) for converting a magnetic signal into an electric signal by using magnetoresistance effects and a pair of electrodes (60) for causing a signal detection current to flow through the magnetoresistive film. A pair of first domain wall suppressing layers (30) are arranged at opposite end portions of the magnetoresistive film, respectively, to apply a longitudinal magnetic bias to the magnetoresistive film. A second domain wall suppressing layer (45) is also provided for applying a longitudinal magnetic bias, which is weaker compared with the longitudinal magnetic bias applied by the first domain wall suppressing layers, to the magnetoresistive film (40).
    Type: Grant
    Filed: September 4, 1992
    Date of Patent: July 25, 1995
    Assignee: Hitachi, Ltd.
    Inventors: Susumu Soeya, Shigeru Tadokoro, Takao Imagawa, Eiji Ashida, Moriaki Fuyama, Shinji Narishige, Kouichi Nishioka
  • Patent number: 5214840
    Abstract: A method of fabricating a thin film magnetic head including a bottom magnetic core formed on a substrate, a top magnetic core laminated through an insulation layer, with one end of the top and bottom magnetic cores being joined and another end forming a magnetic gap, and a conductor coil layer which winds around the joined section for a plurality of number of turns. At least one of the top and bottom magnetic cores has its magnetization easy axis oriented substantially orthogonal to the magnetic path direction of the magnetic head by the magnetic annealing process, so that the magnetic head has an increased output and an enhanced write ability.
    Type: Grant
    Filed: July 10, 1990
    Date of Patent: June 1, 1993
    Assignee: Hitachi, Ltd.
    Inventors: Takao Imagawa, Masaaki Sano, Katsuya Mitsuoka, Kouichi Nishioka, Shinji Narishige, Tetsuo Kobayashi
  • Patent number: 5109312
    Abstract: A magnetic recording apparatus with a magnetic head, superconductive layers formed over at least flux generating surfaces of the magnetic head and normal conductive regions of small size for passing the flux provided in the superconductive layers, over the flux generating surfaces, so as not to form a closed magnetic circuit so as to enable reversible spontaneous magnetization in a magnetic recording medium proximate thereto. The minimum unit size (recording wavelength) of the reversible spontaneous magnetization in magnetic recording of the magnetic recording medium can be reduced from the order of 1 .mu.m to that of 0.1 .mu.m. Thus it is possible to increase the surface recording density of the magnetic recording medium utilizing more than 100 Mb/in.sup.2, comparable to the density achieved by the opto-magnetic recording. This in turn makes it possible to provide a large disc apparatus having a capacity of 60 MB or more.
    Type: Grant
    Filed: March 19, 1990
    Date of Patent: April 28, 1992
    Assignee: Hitachi, Ltd.
    Inventors: Takahiko Kato, Jiro Kuniya, Takao Imagawa, Katsuzo Aihara
  • Patent number: 5051856
    Abstract: A thin film magnetic head has magnetic films, at least one of which is composed of a material containing major components of nickel and iron and one or more element from nitrogen, oxygen and carbon and has two of face-centered cubic system and body-centered tetragonal system, whereby thin film magnetic heads having a high permeability and low coercive force can be provided.
    Type: Grant
    Filed: October 12, 1989
    Date of Patent: September 24, 1991
    Assignee: Hitachi, Ltd.
    Inventors: Shinji Narishige, Katsuya Mitsuoka, Takao Imagawa, Kouichi Nishioka, Akira Kumagai, Masaaki Sano, Yutaka Sugita, Reiko Arai, Tetsuo Kobayashi, Toshihiro Yoshida, Yokuo Saitoh, Yoshikazu Tsuji, Masaaki Hayashi
  • Patent number: 4943883
    Abstract: A thin film magnetic head provided with a first and a second thin film made of a magnetic material, disposed so as to form a closed magnetic circuit; and an intermediate film made of a non-magnetic material, disposed between the first and the second thin films so as to form a magnetic gap at a part of the magnetic circuit; wherein at least one of the first and the second thin films is made of a quaternary amorphous magnetic alloy, whose principal component is cobalt and which contains hafnium, tantalum and palladium.
    Type: Grant
    Filed: November 2, 1988
    Date of Patent: July 24, 1990
    Assignee: Hitachi, Ltd.
    Inventors: Masaaki Sano, Takao Imagawa, Kouichi Nishioka, Shinji Narishige, Masanobu Hanazono, Takashi Onishi, Toshihiro Yoshida
  • Patent number: 4939610
    Abstract: A thin film magnetic head is disclosed which includes a substrate, a first magnetic core disposed on the substrate, a second magnetic core forming a magnetic path in conjunction with the first magnetic core, a conductor coil wound in the magnetic path and a gap formed between ends of the first magnetic core and the second magnetic core. At least one of the first magnetic core and the second magnetic core includes a thin film of a cobalt alloy. The cobalt alloy includes 20-70 atomic percent of cobalt, 20-60 atomic percent of nickel, 12-30 atomic percent of iron and 5-32 atomic percent of palladium.
    Type: Grant
    Filed: October 3, 1988
    Date of Patent: July 3, 1990
    Assignee: Hitachi, Ltd.
    Inventors: Shinji Narishige, Masaaki Sano, Kouichi Nishioka, Takao Imagawa, Masanobu Hanazono, Tetsuo Kobayashi, Toshihiro Yoshida