Patents by Inventor Soichi Oikawa

Soichi Oikawa 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: 20180145247
    Abstract: A magnetic memory of an embodiment includes: a first terminal to third terminals; a first nonmagnetic layer, which is conductive, including a first portion, a second portion, and a third portion, the first portion being disposed between the second portion and the third portion, the second portion being electrically connected to the first terminal, and the third portion being electrically connected to the second terminal; a first magnetoresistive element including a first magnetic layer electrically connected to the third terminal, a second magnetic layer disposed between the first magnetic layer and the first portion, and a second nonmagnetic layer disposed between the first magnetic layer and the second magnetic layer; and a first layer at least disposed between the first portion and the second magnetic layer, and including at least one of Mg, Al, Si, Hf, or a rare earth element, and at least one of oxygen or nitrogen.
    Type: Application
    Filed: January 19, 2018
    Publication date: May 24, 2018
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Yoshiaki SAITO, Hiroaki Yoda, Yushi Kato, Mizue Ishikawa, Soichi Oikawa
  • Publication number: 20180040807
    Abstract: A magnetic memory of an embodiment includes: a first terminal to third terminals; a first nonmagnetic layer, which is conductive, including a first portion, a second portion, and a third portion, the first portion being disposed between the second portion and the third portion, the second portion being electrically connected to the first terminal, and the third portion being electrically connected to the second terminal; a first magnetoresistive element including a first magnetic layer electrically connected to the third terminal, a second magnetic layer disposed between the first magnetic layer and the first portion, and a second nonmagnetic layer disposed between the first magnetic layer and the second magnetic layer; and a first layer at least disposed between the first portion and the second magnetic layer, and including at least one of Mg, Al, Si, Hf, or a rare earth element, and at least one of oxygen or nitrogen.
    Type: Application
    Filed: February 28, 2017
    Publication date: February 8, 2018
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Yoshiaki SAITO, Hiroaki Yoda, Yushi Kato, Mizue Ishikawa, Soichi Oikawa
  • Publication number: 20170194026
    Abstract: According to one embodiment, a perpendicular magnetic recording medium includes a substrate, an underlayer including projections arranged at an average interval of 3 to 20 nm, an amorphous magnetic recording layer having a plurality of columnar magnetic grains on the surface of the projections, each having a magnetization easy axis in a direction perpendicular to a surface of the underlayer. The underlayer is formed such that 0.5d?r?1.5d, where r is the radius of curvature of a vertical section of each projection and d is the average interval between the projections.
    Type: Application
    Filed: March 4, 2016
    Publication date: July 6, 2017
    Applicants: Kabushiki Kaisha Toshiba, Kabushiki Kaisha Toshiba
    Inventors: Kaori Kimura, Soichi Oikawa, Takeshi Iwasaki
  • Patent number: 9633684
    Abstract: According to one embodiment, a magnetic recording medium includes a silicon oxide underlayer having a recess pattern having a plurality of recesses, a nonmagnetic underlayer having a first hole pattern having a plurality of holes corresponding to the recess pattern, and a magnetic recording layer having a second hole pattern having a plurality of holes connected with the first hole pattern. The silicon oxide underlayer, the nonmagnetic underlayer, and the magnetic recording layer are formed in order on the substrate.
    Type: Grant
    Filed: October 30, 2014
    Date of Patent: April 25, 2017
    Assignee: KABUSHIKI KAISHA TOSHIBA
    Inventors: Akira Watanabe, Soichi Oikawa
  • Publication number: 20170004855
    Abstract: According to one embodiment, a perpendicular magnetic recording medium includes an underlying layer with convexes arranged with 1 to 20 nm intervals, and a multilayered amorphous magnetic recording layer formed on the underlying layer. The multilayered amorphous magnetic recording layer includes a first amorphous magnetic recording layer with a plurality of magnetic grains each formed on a corresponding convex to be widened toward its tip and being separated from each other at least in the convex side, a nonmagnetic protective layer covering at least a part of a sidewall of the magnetic particle, and a second amorphous magnetic recording layer formed on the nonmagnetic protective layer.
    Type: Application
    Filed: August 31, 2015
    Publication date: January 5, 2017
    Inventors: Kaori Kimura, Soichi Oikawa
  • Publication number: 20160064023
    Abstract: According to one embodiment, a magnetic recording medium includes a silicon oxide underlayer having a recess pattern having a plurality of recesses, a nonmagnetic underlayer having a first hole pattern having a plurality of holes corresponding to the recess pattern, and a magnetic recording layer having a second hole pattern having a plurality of holes connected with the first hole pattern. The silicon oxide underlayer, the nonmagnetic underlayer, and the magnetic recording layer are formed in order on the substrate.
    Type: Application
    Filed: October 30, 2014
    Publication date: March 3, 2016
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Akira WATANABE, Soichi Oikawa
  • Publication number: 20150162042
    Abstract: According to one embodiment, a perpendicular magnetic recording medium includes a substrate, an underlayer formed on the substrate and a magnetic recording layer formed on the underlayer and having an easy axis in a direction perpendicular to a film surface. The underlayer includes a plurality of projecting portions arranged at a distance of 1 nm to 20 nm from one another. The magnetic recording layer is an amorphous magnetic recording layer including a plurality of magnetic grains each formed to expand towards a top end thereof from a surface of a respective projecting portion of the underlayer, at least those of the magnetic grains located on a respective projecting portion side being separated from each other.
    Type: Application
    Filed: September 25, 2014
    Publication date: June 11, 2015
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Kaori Kimura, Soichi Oikawa, Kazutaka Takizawa, Akira Fujimoto, Akihiko Takeo
  • Publication number: 20150103440
    Abstract: According to one embodiment, a perpendicular magnetic recording medium includes an underlayer in which the width of the grain boundary between crystal grains is less than 0.5 nm, and a multilayered magnetic recording layer formed in contact with the underlayer by alternately stacking at least two magnetic layers and two nonmagnetic layers, which are sequentially provided on a substrate. Each of the magnetic layers is a magnetically continuous layer. The magnetic layer includes magnetic crystal grains mainly containing Co, and a plurality of pinning sites made of an oxide dispersed in the entire magnetic layer. The perpendicular magnetic recording medium has a magnetic characteristic having a magnetization curve with a slope ? of 5 or more near the coercive force.
    Type: Application
    Filed: September 29, 2014
    Publication date: April 16, 2015
    Applicant: Kabushiki Kaisha Toshiba
    Inventor: Soichi OIKAWA
  • Patent number: 8877360
    Abstract: According to one embodiment, a perpendicular magnetic recording medium includes a substrate, and a multilayered magnetic recording layer formed on the substrate by alternately stacking two or more magnetic layers and two or more nonmagnetic layers. The magnetic layers and nonmagnetic layers of the multilayered magnetic recording layer are continuous layers. The magnetic layer includes a magnetic material portion, and a plurality of pinning sites dispersed in the magnetic material portion and made of a nonmagnetic metal different from a nonmagnetic material as a main component of the nonmagnetic layer. This perpendicular magnetic recording medium has magnetic characteristics by which a gradient ? of a magnetization curve near the coercive force is 5 or more.
    Type: Grant
    Filed: November 23, 2011
    Date of Patent: November 4, 2014
    Assignee: Kabushiki Kaisha Toshiba
    Inventor: Soichi Oikawa
  • Patent number: 8817419
    Abstract: According to one embodiment, a magnetic recording head includes a main magnetic pole generating a recording magnetic field in a magnetic recording medium, a return yoke paired with the main magnetic pole, and a spin torque oscillator interposed between the main magnetic pole and the return yoke and including a spin injection layer, an oscillation layer, a nonmagnetic metal layer, and spin assist layer stacked in this order, wherein the nonmagnetic metal layer includes at least one metal selected from the group consisting of Cu, Au, Ag, Al, Pd, Pt, Os, and Ir, and the spin assist layer is a soft magnetic layer whose saturation magnetic flux density (Bs), diamagnetic field coefficient (N) and gap magnetic field (Hg) show a relationship expressed by Bs×N>Hg.
    Type: Grant
    Filed: June 28, 2011
    Date of Patent: August 26, 2014
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Soichi Oikawa, Katsuhiko Koui
  • Patent number: 8786973
    Abstract: According to one embodiment, a thermally assisted magnetic recording method performs heating at a temperature higher than the ambient temperature of the perpendicular recording medium and lower than a temperature at which a nucleation magnetic field Hn of the recording portion is 0, decreases a coercive force Hc of a recording portion by heating a perpendicular recording medium, and records magnetic information by applying a recording magnetic field from a recording magnetic pole to the recording portion having the decreased coercive force.
    Type: Grant
    Filed: August 28, 2012
    Date of Patent: July 22, 2014
    Assignee: Kabushiki Kaisha Toshiba
    Inventor: Soichi Oikawa
  • Patent number: 8748017
    Abstract: According to one embodiment, a bit patterned medium includes a substrate, and a magnetic recording layer disposed above the substrate and including patterns of protrusions. Each of the protrusions contains a plurality of crystal grains. An average distance between the crystal grains is 0.5 to 3.0 nm in each of the protrusions. The protrusions include first protrusions each having a length of 1 ?m or more in a radial direction of the medium and second protrusions each having a length in the radial direction shorter than the length of the first protrusion in the radial direction. Each of the first protrusions has a nucleation field Hn for magnetization reversal and a coercive force Hc satisfying the inequalities, Hn?1.5 kOe and 0.5 kOe?Hc?Hn?1.5 kOe.
    Type: Grant
    Filed: July 1, 2011
    Date of Patent: June 10, 2014
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Masatoshi Sakurai, Yousuke Isowaki, Soichi Oikawa
  • Patent number: 8553359
    Abstract: A magnetic recording head includes a magnetic pole, a spin torque oscillator, a first shield and a second shield. The magnetic pole has an air-bearing surface. The spin torque oscillator is provided so that a first side of the spin torque oscillator faces the magnetic pole in a first direction parallel to the air-bearing surface. The first shield includes a granular magnetic material, and is provided so that two portions of the first shield sandwich the spin torque oscillator in a second direction which is parallel to the air-bearing surface and perpendicular to the first direction. The second shield is provided on a second side of the spin torque oscillator opposite to the first side.
    Type: Grant
    Filed: August 10, 2010
    Date of Patent: October 8, 2013
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Kenichiro Yamada, Katsuhiko Koui, Mariko Kitazaki, Masayuki Takagishi, Tomomi Funayama, Masahiro Takashita, Soichi Oikawa, Akihiko Takeo
  • Publication number: 20130250449
    Abstract: According to one embodiment, a thermally assisted magnetic recording method performs heating at a temperature higher than the ambient temperature of the perpendicular recording medium and lower than a temperature at which a nucleation magnetic field Hn of the recording portion is 0, decreases a coercive force Hc of a recording portion by heating a perpendicular recording medium, and records magnetic information by applying a recording magnetic field from a recording magnetic pole to the recording portion having the decreased coercive force.
    Type: Application
    Filed: August 28, 2012
    Publication date: September 26, 2013
    Applicant: Kabushiki Kaisha Toshiba
    Inventor: Soichi OIKAWA
  • Patent number: 8488373
    Abstract: A spin transfer (torque) oscillator (STO) with a non-magnetic spacer formed between a spin injection layer (SIL) and a field generation layer (FGL), and with an interfacial layer comprised of Fe(100-V)CoV where v is from 5 to 100 atomic % formed between the SIL and non-magnetic spacer is disclosed. A composite seed layer made of Ta and a metal layer having a fcc(111) or hcp(001) texture is used to enhance perpendicular magnetic anisotropy (PMA) in the STO device. The interfacial layer quenches SIL oscillations and thereby stabilizes the SIL against FGL oscillations. The interfacial layer preferably has a thickness from 5 to 50 Angstroms and enhances amplitude (dR/R) in the STO device. The STO device may have a top SIL or bottom SIL configuration. The SIL is typically a laminated structure such as (Co/Ni)X where x is between 5 and 50.
    Type: Grant
    Filed: October 3, 2011
    Date of Patent: July 16, 2013
    Assignees: TDK Corporation, Kabushiki Kaisha Toshiba
    Inventors: Kunliang Zhang, Min Li, Yuchen Zhou, Soichi Oikawa, Hitoshi Iwasaki, Kenichiro Yamada, Katsuhiko Koui
  • Patent number: 8472140
    Abstract: A magnetic recorder includes: a magnetic recording medium; a reproducing head; a magnetic recording head including: a main magnetic pole; a first magnetic layer containing a TM alloy; a second magnetic layer containing a TM alloy or an RE-TM alloy; a third magnetic layer containing an RE-TM alloy; a first intermediate layer provided between the first magnetic layer and the second magnetic layer; and a second intermediate layer provided between the second magnetic layer and the third magnetic layer; and a signal processing portion which performs signal writing into the magnetic recording medium by using the magnetic recording head and reading from the magnetic recording medium by using the reproducing head.
    Type: Grant
    Filed: February 24, 2012
    Date of Patent: June 25, 2013
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Kenichiro Yamada, Hitoshi Iwasaki, Masayuki Takagishi, Tomomi Funayama, Masahiro Takashita, Katsuhiko Koui, Mariko Kitazaki, Soichi Oikawa
  • Patent number: 8467148
    Abstract: A spin torque oscillator includes an amorphous soft magnetic layer, a nonmagnetic layer and a hard magnetic layer. The nonmagnetic layer with a close-packed crystal structure is provided on the amorphous soft magnetic layer. The hard magnetic layer with a close-packed crystal structure and perpendicular magnetic anisotropy is provided on the nonmagnetic layer.
    Type: Grant
    Filed: October 6, 2009
    Date of Patent: June 18, 2013
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Hitoshi Iwasaki, Soichi Oikawa, Katsuhiko Koui, Kenichiro Yamada
  • Patent number: 8446691
    Abstract: According to one embodiment, a magnetic recording device includes a magnetic recording head and a magnetic recording medium. The magnetic recording head includes a main magnetic pole, a shield and a stacked structure. The main magnetic pole has a medium facing surface and a main magnetic pole side surface. The shield has a shield side surface. The stacked structure is provided between the main magnetic pole and shield, and includes first and second magnetic layers, and an intermediate layer. The magnetic recording medium includes a backing layer and a magnetic recording layer. A distance between an end portion of the medium facing surface on a side of the stacked structure and the backing layer is twice or more of a distance between the main magnetic pole side surface and the shield side surface.
    Type: Grant
    Filed: April 30, 2012
    Date of Patent: May 21, 2013
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Masayuki Takagishi, Hitoshi Iwasaki, Kenichiro Yamada, Katsuhiko Koui, Tomomi Funayama, Masahiro Takashita, Mariko Kitazaki, Soichi Oikawa
  • Publication number: 20130082787
    Abstract: A spin transfer (torque) oscillator (STO) with a non-magnetic spacer formed between a spin injection layer (SIL) and a field generation layer (FGL), and with an interfacial layer comprised of Fe(100-V)CoV where v is from 5 to 100 atomic % formed between the SIL and non-magnetic spacer is disclosed. A composite seed layer made of Ta and a metal layer having a fcc(111) or hcp(001) texture is used to enhance perpendicular magnetic anisotropy (PMA) in the STO device. The interfacial layer quenches SIL oscillations and thereby stabilizes the SIL against FGL oscillations. The interfacial layer preferably has a thickness from 5 to 50 Angstroms and enhances amplitude (dR/R) in the STO device. The STO device may have a top SIL or bottom SIL configuration. The SIL is typically a laminated structure such as (Co/Ni)X where x is between 5 and 50.
    Type: Application
    Filed: October 3, 2011
    Publication date: April 4, 2013
    Inventors: Kunliang Zhang, Min Li, Yuchen Zhou, Soichi Oikawa, Hitoshi Iwasaki, Kenichiro Yamada, Katsuhiko Koui
  • Patent number: 8320079
    Abstract: It is made possible to reduce the write magnetic field generated from the main magnetic pole toward the spin torque oscillator, so as to reduce the variation in the oscillation characteristics of the spin torque oscillator, and reduce the current required for oscillation. The magnetic head assembly includes: a recording magnetic pole; a spin torque oscillator that has first and second magnetic layers, and an intermediate layer interposed between the first and second magnetic layers, the spin torque oscillator generating a high-frequency magnetic field by applying a current between the first and second magnetic layers; and a third magnetic layer that is placed adjacent to at least part of a side face of the second magnetic layer.
    Type: Grant
    Filed: June 17, 2009
    Date of Patent: November 27, 2012
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Hitoshi Iwasaki, Kenichiro Yamada, Masayuki Takagishi, Tomomi Funayama, Masahiro Takashita, Mariko Shimizu, Soichi Oikawa, Katsuhiko Koui