Patents by Inventor Ikuko Takekuma

Ikuko Takekuma 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: 20060076233
    Abstract: A reactive sputtering method is provided for producing a magnetic layer in a stable manner with good reproducibility. One aspect of the invention is to form a magnetic layer for a magnetic recording medium without adversely affecting magnetic properties. Carbon oxide gas is added at the time of reactive sputtering. In one embodiment, a method for producing a magnetic recording medium includes forming at least a soft magnetic layer and a magnetic layer above a substrate, wherein forming said magnetic layer includes sputtering with argon gas and carbon oxide gas.
    Type: Application
    Filed: October 6, 2005
    Publication date: April 13, 2006
    Applicant: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Yoshinori Honda, Ikuko Takekuma, Ichiro Tamai
  • Publication number: 20060057431
    Abstract: Embodiments of the embodiment are directed to reducing the inter-granular exchange coupling of an oxide granular medium and obtaining a high media S/N value, resulting in an areal recording density greater than 23 gigabits per square centimeter or more being achieved. In one embodiment, a magnetic recording medium comprises a structure laminating a soft-magnetic underlayer, a lower intermediate layer including Ru, an upper intermediate layer consisting of Ru crystal grains and oxide crystal grain boundaries, a magnetic recording layer consisting of crystal grains and oxide crystal grain boundaries, in order, on a substrate, growing crystal grains of the magnetic recording layer epitaxially on the Ru crystal grains of the upper intermediate layer, and growing the crystal grain boundaries of the magnetic recording layer on the crystal grain boundaries of the upper intermediate layer.
    Type: Application
    Filed: September 14, 2005
    Publication date: March 16, 2006
    Applicant: Hitachi Global Storage Technologies Netherlands B.V.
    Inventors: Ichiro Tamai, Ikuko Takekuma, Yoshiyuki Hirayama, Yuzuru Hosoe, Yoshinori Honda
  • Publication number: 20050227121
    Abstract: A perpendicular magnetic recording medium includes an intermediate film formed of a plurality of layers between a soft magnetic film and a perpendicular magnetization film. The intermediate film includes at least two layers, i.e., an oxygen-containing layer, or a nonmetallic element-containing layer containing nitrogen, silicon or carbon, and a metallic layer formed on a surface side of the oxygen-containing layer or the nonmetallic element-containing layer. The metallic layer includes a plurality of isolated island-shaped structures. Crystal grains of the perpendicular magnetization film are formed so as to correspond to the isolated island-shaped structures. As a result, a high recording density is obtained.
    Type: Application
    Filed: June 9, 2005
    Publication date: October 13, 2005
    Inventors: Yoshiyuki Hirayama, Hiroyuki Nakagawa, Hiroaki Nemoto, Ichiro Tamai, Ikuko Takekuma
  • Patent number: 6916557
    Abstract: A perpendicular magnetic recording medium includes an intermediate film formed of a plurality of layers between a soft magnetic film and a perpendicular magnetization film. The intermediate film includes at least two layers, i.e., an oxygen-containing layer, or a nonmetallic element-containing layer containing nitrogen, silicon or carbon, and a metallic layer formed on a surface side of the oxygen-containing layer or the nonmetallic element-containing layer. The metallic layer includes a plurality of isolated island-shaped structures. Crystal grains of the perpendicular magnetization film are formed so as to correspond to the isolated island-shaped structures. As a result, a high recording density is obtained.
    Type: Grant
    Filed: February 25, 2003
    Date of Patent: July 12, 2005
    Assignee: Hitachi Global Storage Technologies Japan, Ltd.
    Inventors: Yoshiyuki Hirayama, Hiroyuki Nakagawa, Hiroaki Nemoto, Ichiro Tamai, Ikuko Takekuma
  • Publication number: 20050142388
    Abstract: Embodiments of the invention provide a perpendicular magnetic recording medium that not only attains the magnetic isolation of crystal grains in a magnetic recording layer from one another in a region of the medium in which the thickness of an intermediate layer is equal to or smaller than about 20 nm but also exhibits excellent crystallographic texture and that exhibits small medium noise, excellent thermal stability, and high write-ability. In one embodiment, a perpendicular magnetic recording medium has at least a soft-magnetic underlayer, a first intermediate layer, a second intermediate layer, a third intermediate layer, and a magnetic recording layer successively formed on a substrate.
    Type: Application
    Filed: October 29, 2004
    Publication date: June 30, 2005
    Applicant: Hitachi Global Storage Technologies Netherlands, B.V.
    Inventors: Yoshiyuki Hirayama, Yuzuru Hosoe, Hiroyuki Nakagawa, Ikuko Takekuma
  • Publication number: 20050058854
    Abstract: Disclosed here is a perpendicular magnetic recording medium for realizing a high media S/N value without degrading the magnetic isolation of crystal grains from each another. The perpendicular magnetic recording medium comprises a substrate, a soft magnetic underlayer formed on the substrate, an intermediate layer formed on the soft magnetic underlayer, and a magnetic recording layer formed on the intermediate layer. The intermediate layer consists of at least two or more layers and contains Ru or an Ru alloy and the magnetic recording layer is made of a material containing a CoCrPt alloy and oxygen. The crystallo graphic orientation of the recording layer can be improved enough without increasing the crystal grain size if a full width at half-maximum ??50 of the Rocking curves of the Ru (0002) diffraction peak measured by an X-ray diffraction method is 5° and under.
    Type: Application
    Filed: June 25, 2004
    Publication date: March 17, 2005
    Inventors: Ikuko Takekuma, Hiroyuki Nakagawa, Ichiro Tamai, Yoshiyuki Hirayama, Yuzuru Hosoe
  • Publication number: 20040191571
    Abstract: Disclosed are a perpendicular magnetic recording medium with lower medium noise, insusceptible to thermal fluctuation and high recording resolution and a method of manufacturing it. As the step of forming a metal layer at the time of forming a recording layer on a non-magnetic substrate via a plurality of underlayers and the step of forming an oxide layer with an average thickness of 0.2 nm or less are repeated, the crystal grains are magnetically isolated without disturbing the orientation of the crystal grain of the recording layer of the perpendicular magnetic recording medium or without degrading the magnetic characteristic of the crystal grain of the recording layer.
    Type: Application
    Filed: November 6, 2003
    Publication date: September 30, 2004
    Inventors: Yoshiyuki Hirayama, Ichiro Tamai, Takayuki Ichihara, Hiroyuki Nakagawa, Hiroaki Nemoto, Mineaki Kodama, Ikuko Takekuma
  • Publication number: 20040146747
    Abstract: Co/Pd or Co/Pt superlattice is provided to enable magnetic recording devices to sustain good recording/readback performances across a wide range of temperatures. Such a superlattice medium includes a substrate and a magnetic layer formed on the substrate and the magnetic layer comprises multilayer superlattice films of ferromagnetic metal layers which contain Co and paramagnetic metal layers which consist of Pd and/or Pt, wherein the ferromagnetic metal layers further contain a paramagnetic element and the thickness of the paramagnetic metal layers is 0.8 nm or less. When a magnetic torque loop of the perpendicular magnetic recording medium is measured with a torque magnetometer, the polarity of a value of loop components with translational symmetry of 90 degrees should be opposite to the polarity of a value of loop components with translational symmetry of 180 degrees.
    Type: Application
    Filed: July 10, 2003
    Publication date: July 29, 2004
    Applicant: Hitachi, Ltd.
    Inventors: Hiroaki Nemoto, Ikuko Takekuma, Yuzuru Hosoe, Hiroyuki Nakagawa, Masukazu Igarashi
  • Publication number: 20040038083
    Abstract: A perpendicular magnetic recording medium includes an intermediate film formed of a plurality of layers between a soft magnetic film and a perpendicular magnetization film. The intermediate film includes at least two layers, i.e., an oxygen-containing layer, or a nonmetallic element-containing layer containing nitrogen, silicon or carbon, and a metallic layer formed on a surface side of the oxygen-containing layer or the nonmetallic element-containing layer. The metallic layer includes a plurality of isolated island-shaped structures. Crystal grains of the perpendicular magnetization film are formed so as to correspond to the isolated island-shaped structures. As a result, a high recording density is obtained.
    Type: Application
    Filed: February 25, 2003
    Publication date: February 26, 2004
    Applicant: Hitachi, Ltd.
    Inventors: Yoshiyuki Hirayama, Hiroyuki Nakagawa, Hiroaki Nemoto, Ichiro Tamai, Ikuko Takekuma