Patents by Inventor Kiwamu Tanahashi

Kiwamu Tanahashi 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: 9966095
    Abstract: A magnetic media for magnetic data recording having reduced signal noise. The magnetic media includes a magnetic recording layer that has first, second and third portions. The first portion at the bottom of the magnetic recording layer includes an oxide and has a high anisotropy field. The third portion, located at the top of the magnetic recording layer has a low anisotropy field and does not include an oxide. The second portion, located between the first and third portions has an anisotropy field that is between that of the first and third magnetic portions. The second portion includes a thin layer of a material that has an extremely low anisotropy field that is located within a material having a higher magnetic anisotropy.
    Type: Grant
    Filed: August 2, 2016
    Date of Patent: May 8, 2018
    Assignee: WESTERN DIGITAL TECHNOLOGIES, INC.
    Inventors: Shun Tonooka, Masayoshi Shimizu, Maki Maeda, Kiwamu Tanahashi
  • Publication number: 20180040345
    Abstract: A magnetic media for magnetic data recording having reduced signal noise. The magnetic media includes a magnetic recording layer that has first, second and third portions. The first portion at the bottom of the magnetic recording layer includes an oxide and has a high anisotropy field. The third portion, located at the top of the magnetic recording layer has a low anisotropy field and does not include an oxide. The second portion, located between the first and third portions has an anisotropy field that is between that of the first and third magnetic portions. The second portion includes a thin layer of a material that has an extremely low anisotropy field that is located within a material having a higher magnetic anisotropy.
    Type: Application
    Filed: August 2, 2016
    Publication date: February 8, 2018
    Inventors: Shun Tonooka, Masayoshi Shimizu, Maki Maeda, Kiwamu Tanahashi
  • Patent number: 9406328
    Abstract: In one embodiment, a perpendicular magnetic recording medium includes: a substrate; and a soft magnetic underlayer structure positioned above the substrate, where the soft magnetic underlayer includes: a coupling layer; a first soft underlayer positioned above the coupling layer; and a second soft underlayer positioned below the coupling layer, where a difference between a magnetic flux density of the soft magnetic underlayer structure at 25° C. and a magnetic flux density of the soft underlayer structure at 85° C. is less than or equal to about 10% of the magnetic flux density of the soft magnetic underlayer structure at 25° C.
    Type: Grant
    Filed: July 29, 2014
    Date of Patent: August 2, 2016
    Assignee: HGST Netherlands B.V.
    Inventors: Shun Tonooka, Masayoshi Shimizu, Hiroyuki Nakagawa, Kiwamu Tanahashi
  • Publication number: 20160035381
    Abstract: A perpendicular magnetic recording medium with an grain isolation layer is disclosed. In one embodiment, a perpendicular magnetic recording medium comprises a substrate, a soft non-magnetic under layer formed over the substrate, a granular layer comprising an exchange control layer and a recording layer formed over the soft non-magnetic under layer, wherein a difference between a level at 25 deg C. and a level at 85 deg C. of a slope at a coercivity of a magnetization process curve having saturation magnetization normalized at 1 is obtained when a magnetic field is applied perpendicular to said medium, is 10% or less.
    Type: Application
    Filed: August 1, 2014
    Publication date: February 4, 2016
    Inventors: Shun TONOOKA, Masayoshi SHIMIZU, Hiroyuki NAKAGAWA, Kiwamu TANAHASHI
  • Publication number: 20160035380
    Abstract: In one embodiment, a perpendicular magnetic recording medium includes: a substrate; and a soft magnetic underlayer structure positioned above the substrate, where the soft magnetic underlayer includes: a coupling layer; a first soft underlayer positioned above the coupling layer; and a second soft underlayer positioned below the coupling layer, where a difference between a magnetic flux density of the soft magnetic underlayer structure at 25° C. and a magnetic flux density of the soft underlayer structure at 85° C. is less than or equal to about 10% of the magnetic flux density of the soft magnetic underlayer structure at 25° C.
    Type: Application
    Filed: July 29, 2014
    Publication date: February 4, 2016
    Applicant: HGST NETHERLANDS B.V.
    Inventors: Shun Tonooka, Masayoshi Shimizu, Hiroyuki Nakagawa, Kiwamu Tanahashi
  • Publication number: 20150294679
    Abstract: In one embodiment, a perpendicular magnetic recording medium includes an oxide recording layer including an oxide and a non-oxide recording layer which does not contain an oxide positioned above the oxide recording layer. The oxide recording layer includes a first recording layer, a second recording layer, a third recording layer, and a fourth recording layer. Also, an oxide concentration of the first recording layer is greater than an oxide concentration of the second recording layer, an oxide concentration of the third recording layer is greater than an oxide concentration of the fourth recording layer, and the oxide concentration of the third recording layer is greater than the oxide concentration of the second recording layer.
    Type: Application
    Filed: June 2, 2015
    Publication date: October 15, 2015
    Inventors: Shun Tonooka, Kiwamu Tanahashi, Hiroyuki Nakagawa, Ichiro Tamai
  • Patent number: 9058831
    Abstract: In one embodiment, a perpendicular magnetic recording medium includes an oxide recording layer including an oxide and a non-oxide recording layer which does not contain an oxide positioned above the oxide recording layer. The oxide recording layer includes a region R1 where a grain boundary width in a direction parallel to a plane of formation of R1 increases therealong from a lowermost portion of the oxide recording layer toward a medium surface, a region R3 positioned above R1 wherein a grain boundary width increases therealong toward the medium surface, a region R2 where a grain boundary width of R2 decreases therealong from R1 to R3, with R2 being positioned between R1 and R3, and a region R4 where a grain boundary width of R4 decreases therealong from R3 toward the medium surface, with R4 being positioned above R3 and near an uppermost portion of the oxide recording layer.
    Type: Grant
    Filed: December 14, 2011
    Date of Patent: June 16, 2015
    Assignee: HGST Netherlands B.V.
    Inventors: Shun Tonooka, Kiwamu Tanahashi, Hiroyuki Nakagawa, Ichiro Tamai
  • Patent number: 8795478
    Abstract: Embodiments of the invention provide a manufacturing method which permits a high quality perpendicular magnetic recording medium to be manufactured with a high yield by preventing abnormal discharge which sputters particles from the target. In one embodiment, while the perpendicular magnetic recording medium is formed, DC pulses are applied to the target. During the reversal period (Reversal Time) between sputtering periods, a voltage of the opposite polarity is applied. During the sputtering period, a negative voltage is applied which biases the target surface to a negative potential, causing Ar+ to collide with and sputter CoCrPt and SiO2 for deposition on the intermediate layer. The top surface of the insulation material (SiO2) on the target is charged by Ar+ to have a voltage larger than the target voltage. However, arcing can be prevented since the charge on the surface of the insulation material is neutralized due to a positive voltage applied to the target during the non-sputtering period.
    Type: Grant
    Filed: October 18, 2005
    Date of Patent: August 5, 2014
    Assignee: HGST Netherlands B.V.
    Inventors: Yoshinori Honda, Takayuki Ichihara, Hiroyuki Nakagawa, Kiwamu Tanahashi
  • Patent number: 8705208
    Abstract: According to one embodiment, a PMRM includes a substrate, a soft magnetic underlayer above the substrate, an underlayer above the soft magnetic underlayer, an oxide-containing magnetic layer above the underlayer, and a ferromagnetic layer above the magnetic layer having no oxides. The underlayer controls orientation and segregation of the magnetic layer. The oxide-containing magnetic layer comprises at least two or more magnetic layers, a Cr concentration of the magnetic layer adjacent to the ferromagnetic metal layer is between about 23 at. % and about 32 at. %, and a difference between the Cr concentration of the magnetic layer adjacent to the ferromagnetic metal layer and a magnetic layer having a lowest Cr concentration among the at least three magnetic layers is less than about 25 at. %, the magnetic layer with a lowest Cr concentration has a granular structure, and a nucleation field is greater than about 159.2 kA/m.
    Type: Grant
    Filed: June 30, 2010
    Date of Patent: April 22, 2014
    Assignee: HGST Netherlands B.V.
    Inventors: Hiroyuki Nakagawa, Reiko Arai, Ichiro Tamai, Kiwamu Tanahashi
  • Patent number: 8592060
    Abstract: In one embodiment, a perpendicular magnetic recording medium includes a substrate, a soft-magnetic underlayer above the substrate, a seed layer above the soft-magnetic underlayer, a first intermediate layer above the seed layer, a second intermediate layer above the first intermediate layer, a recording layer above the second intermediate layer, and a protective layer above the recording layer. The second intermediate layer includes an Ru alloy having an element selected from a group consisting of: Ti in a range from about 20 at. % to about 50 at. %, Nb in a range from about 20 at. % to about 50 at. %, Al in a range from about 20 at. % to about 40 at. %, Ta in a range from about 30 at. % to about 50 at. %, and Si in a range about 20 at. % to about 40 at. %. Other magnetic media and systems using this media are described according to more embodiments.
    Type: Grant
    Filed: December 21, 2010
    Date of Patent: November 26, 2013
    Assignee: HGST Netherlands B.V.
    Inventors: Ichiro Tamai, Yotsuo Yahisa, Akemi Hirotsune, Kiwamu Tanahashi
  • Publication number: 20130155542
    Abstract: In one embodiment, a perpendicular magnetic recording medium includes an oxide recording layer including an oxide and a non-oxide recording layer which does not contain an oxide positioned above the oxide recording layer. The oxide recording layer includes a region R1 where a grain boundary width in a direction parallel to a plane of formation of R1 increases therealong from a lowermost portion of the oxide recording layer toward a medium surface, a region R3 positioned above R1 wherein a grain boundary width increases therealong toward the medium surface, a region R2 where a grain boundary width of R2 decreases therealong from R1 to R3, with R2 being positioned between R1 and R3, and a region R4 where a grain boundary width of R4 decreases therealong from R3 toward the medium surface, with R4 being positioned above R3 and near an uppermost portion of the oxide recording layer.
    Type: Application
    Filed: December 14, 2011
    Publication date: June 20, 2013
    Applicant: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Shun Tonooka, Kiwamu Tanahashi, Hiroyuki Nakagawa, Ichiro Tamai
  • Patent number: 8440332
    Abstract: Embodiments of the present invention provide a perpendicular magnetic recording medium that reduces the noise of granular recording layers, obtains sufficient overwrite characteristic that suppresses an increase in the magnetic cluster size, and allows high-density recording. According to one embodiment, a perpendicular magnetic recording medium comprising substrate having thereon at least soft magnetic layer, nonmagnetic intermediate layer, a perpendicular recording layer and protective layer formed in that order. The perpendicular recording layer consists of three or more layers of first recording layer, a second recording layer, and a third recording layer from the side nearer to the substrate. The first recording layer and the second recording layer have a granular structure comprising a grain boundary of an oxide surrounding ferromagnetic crystal grains containing Co and Pt, and the third recording layer has a non-granular structure mainly comprising Co and not containing an oxide.
    Type: Grant
    Filed: April 8, 2009
    Date of Patent: May 14, 2013
    Assignee: HGST Netherlands B.V.
    Inventors: Ichiro Tamai, Kiwamu Tanahashi
  • Patent number: 8390956
    Abstract: According to one embodiment, a perpendicular magnetic recording medium includes at least one soft magnetic underlayer above a substrate, a seed layer above the at least one soft magnetic underlayer, an intermediate layer above the seed layer, a magnetic recording layer above the intermediate layer, and an overcoat layer above the magnetic recording layer, wherein the seed layer includes a second seed layer above a first seed layer. In another embodiment, the seed layer is a multilayered structure of at least two cycles of a unit of layered film which includes a first seed layer and a second seed layer. The first seed layer includes a non-magnetic alloy having a Face-Centered-Cubic (FCC) structure, and the second seed layer includes a soft magnetic alloy having a FCC structure. Other structures are also disclosed, according to more embodiments.
    Type: Grant
    Filed: June 3, 2010
    Date of Patent: March 5, 2013
    Assignee: HGST Netherlands B.V.
    Inventors: Shun Tonooka, Reiko Arai, Hiroyuki Nakagawa, Kiwamu Tanahashi
  • Publication number: 20120307395
    Abstract: According to one embodiment, a perpendicular magnetic recording medium includes a first granular recording layer characterized by a magnetic anisotropy Ku1, a second granular recording layer above the first granular recording layer characterized by a magnetic anisotropy Ku2, and a third granular recording layer above the second granular recording layer characterized by a magnetic anisotropy Ku3, wherein Ku3<Ku2>Ku1. In another embodiment, a magnetic medium includes a first recording layer with a first CoCrPt alloy in a first ratio X1, a second recording layer above the first recording layer and having a second CoCrPt alloy in a second ratio X2, and a third recording layer above the second recording layer having a third CoCrPt alloy in a third ratio X3 with each ratio defined as a concentration of Pt divided by a concentration of Cr in the respective CoCrPt alloy, wherein X3<X2>X1.
    Type: Application
    Filed: May 31, 2011
    Publication date: December 6, 2012
    Applicant: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Shun Tonooka, Kiwamu Tanahashi, Hiroyuki Nakagawa, Ichiro Tamai
  • Patent number: 8298688
    Abstract: According to one embodiment, a magnetic recording medium includes a magnetic recording layer formed above a substrate, comprising: a first magnetic layer formed from a [Co/Pt]n multilayered film, wherein the first magnetic layer has a face-centered cubic (fcc) (111) crystal structure, the (111) direction being perpendicular to a film surface thereof, and a second magnetic layer comprising a CoCrPt or CoCrPt alloy film formed above the first magnetic layer, wherein the second magnetic layer has a hexagonal close packed (hcp) (00.1) crystal structure, the (00.1) direction being perpendicular to a film surface thereof. According to another embodiment, a system includes a magnetic recording medium as described above, a magnetic head for reading from and/or writing to the magnetic recording medium, a magnetic head slider for supporting the magnetic head, and a control unit coupled to the magnetic head for controlling operation of the magnetic head.
    Type: Grant
    Filed: November 2, 2010
    Date of Patent: October 30, 2012
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Hiroaki Nemoto, Kiwamu Tanahashi, Hiroyuki Nakagawa
  • Patent number: 8252367
    Abstract: Soft magnetic film fabricated with preferred uniaxial anisotropy for perpendicular recording. One type of cathode design has a field direction that is parallel to the direction of the Hex of the second SUL with a magnetically-pinned first SUL. In addition, SUL structures having low AP exchange energy also are disclosed. The SUL structure combines the cathode field direction of the SUL2 with the pinned SUL1. The SUL1 is magnetically pinned to the pinning layer and the pinning direction is parallel to the direction of the cathode field applied during deposition of the SUL1. High Hc ferro-magnetic materials may be deposited onto a heated substrate that is magnetized along the radial direction by the cathode field. The pinning field may be higher than the cathode field, indicating that the cathode field during deposition of the SUL2 cannot disturb the magnetic state of the SUL1 pinned to pinning layer.
    Type: Grant
    Filed: December 19, 2007
    Date of Patent: August 28, 2012
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Gunn Choe, Yoshihiro Ikeda, Masayoshi Shimizu, Kiwamu Tanahashi
  • Publication number: 20120154948
    Abstract: In one embodiment, a perpendicular magnetic recording medium includes a substrate, a soft-magnetic underlayer above the substrate, a seed layer above the soft-magnetic underlayer, a first intermediate layer above the seed layer, a second intermediate layer above the first intermediate layer, a recording layer above the second intermediate layer, and a protective layer above the recording layer. The second intermediate layer includes an Ru alloy having an element selected from a group consisting of: Ti in a range from about 20 at. % to about 50 at. %, Nb in a range from about 20 at. % to about 50 at. %, Al in a range from about 20 at. % to about 40 at. %, Ta in a range from about 30 at. % to about 50 at. %, and Si in a range about 20 at. % to about 40 at. %. Other magnetic media and systems using this media are described according to more embodiments.
    Type: Application
    Filed: December 21, 2010
    Publication date: June 21, 2012
    Applicant: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Ichiro Tamai, Yotsuo Yahisa, Akemi Hirotsune, Kiwamu Tanahashi
  • Patent number: 8000060
    Abstract: Embodiments of the present invention provide a perpendicular magnetic recording medium having a substrate, a magnetic recording layer and a protective layer. The magnetic recording layer includes a perpendicular recording layer, a magnetic coupling layer and a writing assist layer. The perpendicular recording layer is a Co alloy layer containing an oxide disposed between the magnetic coupling layer and the substrate. The magnetic coupling layer is a ferromagnetic layer disposed between the perpendicular recording layer and the writing assist layer. The writing assist layer is a ferromagnetic layer disposed between the magnetic coupling layer and the protective layer. The saturation magnetization of the magnetic coupling layer is lower than the saturation magnetization of the perpendicular recording layer or the writing assist layer. The thickness of the magnetic coupling layer is 1 nm or more and 3 nm or less.
    Type: Grant
    Filed: January 17, 2008
    Date of Patent: August 16, 2011
    Assignee: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Zhengang Zhang, Ikuko Takekuma, Kiwamu Tanahashi
  • Publication number: 20110151144
    Abstract: Embodiments of the invention provide a perpendicular magnetic recording medium improved for fly ability, high in read signal quality, and capable of suppressing magnetic decay of recorded magnetization to be caused by stray fields. In one embodiment, a perpendicular recording layer is formed over a substrate with a soft magnetic underlayer therebetween, then an amorphous or nano-crystalline layer is formed between the substrate and the soft magnetic underlayer. The soft magnetic underlayer includes first and second amorphous soft magnetic layers, as well as a nonmagnetic layer formed between those first and second amorphous soft magnetic layers. The first and second amorphous soft magnetic layers are given uniaxial anisotropy in the radial direction of the substrate respectively and coupled with each other antiferromagnetically.
    Type: Application
    Filed: December 15, 2010
    Publication date: June 23, 2011
    Applicant: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Reiko Arai, Kiwamu Tanahashi, Yoshinori Honda, Mineaki Kodama
  • Publication number: 20110122525
    Abstract: According to one embodiment, a magnetic recording medium includes a magnetic recording layer formed above a substrate, comprising: a first magnetic layer formed from a [Co/Pt]n multilayered film, wherein the first magnetic layer has a face-centered cubic (fcc) (111) crystal structure, the (111) direction being perpendicular to a film surface thereof, and a second magnetic layer comprising a CoCrPt or CoCrPt alloy film formed above the first magnetic layer, wherein the second magnetic layer has a hexagonal close packed (hcp) (00.1) crystal structure, the (00.1) direction being perpendicular to a film surface thereof. According to another embodiment, a system includes a magnetic recording medium as described above, a magnetic head for reading from and/or writing to the magnetic recording medium, a magnetic head slider for supporting the magnetic head, and a control unit coupled to the magnetic head for controlling operation of the magnetic head.
    Type: Application
    Filed: November 2, 2010
    Publication date: May 26, 2011
    Applicant: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Hiroaki Nemoto, Kiwamu Tanahashi, Hiroyuki Nakagawa