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).
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Patent number: 10276192Abstract: A magnetic recording medium includes an amorphous buffer layer, a hybrid layer including a barrier layer, and a texture control layer. The magnetic recording medium also includes a heat sink layer, an under layer, and a perpendicular recording layer.Type: GrantFiled: July 11, 2013Date of Patent: April 30, 2019Assignee: Western Digital Technologies, Inc.Inventors: Akemi Hirotsune, Ikuko Takekuma, Junichi Sayama
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Patent number: 9472228Abstract: A magnetic medium for perpendicular magnetic data recording having improved corrosion characteristics and reduced surface roughness. The magnetic medium includes an under-layer and a perpendicular magnetic recording layer formed over the under-layer. The under-layer can be formed of MgO and has an oxygen concentration that is greater at the perpendicular magnetic recording layer than it is away from the perpendicular magnetic recording layer.Type: GrantFiled: May 28, 2013Date of Patent: October 18, 2016Assignee: HGST Netherlands B.V.Inventors: Akemi Hirotsune, Ikuko Takekuma, Hiroyuki Matsumoto, Oleksandr Mosendz
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Publication number: 20160118071Abstract: In one embodiment, a perpendicular magnetic recording medium includes: a substrate; an underlayer positioned above the substrate; and a magnetic recording layer structure positioned above the underlayer, where the magnetic recording layer structure includes at least a first magnetic recording layer and a second magnetic recording layer, the second magnetic layer being positioned above first magnetic recording layer, where the first magnetic recording layer includes a first segregant material positioned between magnetic grains thereof, the first segregant material being primarily boron nitride (BN), and where the second magnetic recording layer includes a second segregant material positioned between the magnetic grains thereof, the second segregant material being primarily an oxide.Type: ApplicationFiled: October 23, 2014Publication date: April 28, 2016Applicant: HGST NETHERLANDS B.V.Inventors: Akemi Hirotsune, Ikuko Takekuma, Naoto Ito, Hiroyuki Matsumoto
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Patent number: 9117477Abstract: A magnetic medium for perpendicular magnetic data recording, having improved magnetic properties through use of a novel seed layer. The magnetic medium includes a substrate having a seed layer, a magnetic under-layer and a magnetic recording layer formed there-over. The seed layer includes an element selected from a first group of Cr, Co, Fe and Ni, and at least one element that is selected from the other elements of the first group or from a second group consisting of W, Mo and Ru. A buffer layer may be included between the substrate and the seed layer.Type: GrantFiled: May 8, 2013Date of Patent: August 25, 2015Assignee: HGST Netherlands B.V.Inventors: Akemi Hirotsune, Ikuko Takekuma, Hiroaki Nemoto
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Publication number: 20150017480Abstract: A magnetic recording medium includes an amorphous buffer layer, a hybrid layer including a barrier layer, and a texture control layer. The magnetic recording medium also includes a heat sink layer, an under layer, and a perpendicular recording layer.Type: ApplicationFiled: July 11, 2013Publication date: January 15, 2015Inventors: Akemi Hirotsune, Ikuko Takekuma, Junichi Sayama
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Publication number: 20140355156Abstract: A magnetic medium for perpendicular magnetic data recording having improved corrosion characteristics and reduced surface roughness. The magnetic medium includes an under-layer and a perpendicular magnetic recording layer formed over the under-layer. The under-layer can be formed of MgO and has an oxygen concentration that is greater at the perpendicular magnetic recording layer than it is away from the perpendicular magnetic recording layer.Type: ApplicationFiled: May 28, 2013Publication date: December 4, 2014Applicant: HGST Netherlands B.V.Inventors: Akemi Hirotsune, Ikuko Takekuma, Hiroyuki Matsumoto, Oleksandr Mosendz
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Publication number: 20140334039Abstract: A magnetic medium for perpendicular magnetic data recording, having improved magnetic properties through use of a novel seed layer. The magnetic medium includes a substrate having a seed layer, a magnetic under-layer and a magnetic recording layer formed there-over. The seed layer includes an element selected from a first group of Cr, Co, Fe and Ni, and at least one element that is selected from the other elements of the first group or from a second group consisting of W, Mo and Ru. A buffer layer may be included between the substrate and the seed layer.Type: ApplicationFiled: May 8, 2013Publication date: November 13, 2014Applicant: HGST Netherlands B.V.Inventors: Akemi Hirotsune, Ikuko Takekuma, Hiroaki Nemoto
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Patent number: 8771849Abstract: Embodiments of the present invention help allow accurate control of the magnetization reversal in a magnetic recording layer in small reversal units, whereby high-density recording can be achieved. According to one embodiment, by forming an intermediate layer having a granular structure similar to that of the magnetic recording layer below the magnetic recording layer, a continuous crystal grain boundary is formed at the interface between the magnetic recording layer and the intermediate layer, thereby preventing incomplete formation of the crystal grain boundary found in the initial growth layer of the magnetic recording layer. The intermediate layer comprises a non-magnetic alloy comprising Co and Cr as its main components and an oxide such as Al, Cr, Hf. Mg, Nb, Si, Ta, Ti and Zr. Further, the average content of the oxygen element in the intermediate layer is in the range from 6 at % to 20 at %.Type: GrantFiled: October 21, 2008Date of Patent: July 8, 2014Assignee: HGST Netherlands B.V.Inventors: Hiroaki Nemoto, Ikuko Takekuma, Ichiro Tamai, Yoshiyuki Hirayama
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Patent number: 8709618Abstract: According to embodiments of the present invention, a shielded pole writer and a perpendicular magnetic recording medium suitable thereto are combined to provide high medium SNR and excellent OW characteristic simultaneously. A perpendicular magnetic recording medium of a magnetic storage apparatus mounting a shielded pole writer, including a perpendicular magnetic recording medium having a recording layer of a three layered structure is used. A first recording layer has a granular structure consisting of grain boundaries containing an oxide and columnar grains comprising a CoCrPt alloy, in which a second recording layer and a third recording layer formed thereabove comprise Co as a main ingredient, contain Cr and do not contain an oxide, and the Cr concentration in the second recording layer is lower than the Cr concentration in the third recording layer.Type: GrantFiled: March 20, 2007Date of Patent: April 29, 2014Assignee: HGST Netherlands B.V.Inventors: Ikuko Takekuma, Hiroyuki Nakagawa, Hiroaki Nemoto, Yoshiyuki Hirayama
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Patent number: 8679654Abstract: Surface flatness of magnetic recording medium to which a magnetic recording layer made of L10 FePt magnetic alloy thin film, with distance between a magnetic head and a magnetic recording medium sufficiently reduced. The magnetic recording layer includes: magnetic layers containing a magnetic alloy including Fe and Pt as principal materials; and one non-magnetic material selected from carbon, oxide and nitride. The first magnetic layer disposed closer to a substrate has a granular structure in which magnetic alloy grains including FePt alloy as the principal material are separated from grain boundaries including the non-magnetic material as the principal material. The second magnetic layer disposed closer to the surface than the first magnetic layer is fabricated so as to have a homogeneous structure in which an FePt alloy and the non-magnetic material are mixed in a state finer than diameters of the FePt magnetic alloy grains in the first magnetic layer.Type: GrantFiled: February 13, 2012Date of Patent: March 25, 2014Assignee: Hitachi, Ltd.Inventors: Hiroaki Nemoto, Ikuko Takekuma, Kimio Nakamura, Junichi Sayama
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Publication number: 20120225325Abstract: Surface flatness of magnetic recording medium to which a magnetic recording layer made of L10 FePt magnetic alloy thin film, with distance between a magnetic head and a magnetic recording medium sufficiently reduced. The magnetic recording layer includes: magnetic layers containing a magnetic alloy including Fe and Pt as principal materials; and one non-magnetic material selected from carbon, oxide and nitride. The first magnetic layer disposed closer to a substrate has a granular structure in which magnetic alloy grains including FePt alloy as the principal material are separated from grain boundaries including the non-magnetic material as the principal material. The second magnetic layer disposed closer to the surface than the first magnetic layer is fabricated so as to have a homogeneous structure in which an FePt alloy and the non-magnetic material are mixed in a state finer than diameters of the FePt magnetic alloy grains in the first magnetic layer.Type: ApplicationFiled: February 13, 2012Publication date: September 6, 2012Inventors: HIROAKI NEMOTO, Ikuko TAKEKUMA, Kimio NAKAMURA, Junichi SAYAMA
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Publication number: 20120214021Abstract: There is provided a magnetic recording medium including an MgO underlayer that can be formed by a mass production process and has a thickness of 3 nm or less as well as including a magnetic recording layer made of an L10-type FePt ordered alloy having excellent magnetic properties. A conductive compound having a crystal structure belonging to a cubic system is used as a material of an underlayer provided at the bottom of the MgO underlayer. The thickness of the MgO layer is 1 nm or more and 3 nm or less.Type: ApplicationFiled: February 2, 2012Publication date: August 23, 2012Inventors: Junichi Sayama, Ikuko Takekuma, Hiroaki Nemoto
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Publication number: 20120052330Abstract: A perpendicular magnetic recording medium having sufficient perpendicular uniaxial magnetic anisotropy energy and a crystal grain size for realizing an areal recording density of one terabit or more per one square centimeter, and excellent in mass productivity, and a manufacturing method of the same are provided. On a substrate, a substrate-temperature control layer, an underlayer and a magnetic recording layer are sequentially formed. The magnetic recording layer is formed by repeating a magnetic layer stacking step N times (N?2), which includes a first step of heating the substrate in a heat process chamber, and a second step of depositing, in a deposition process chamber, the magnetic recording layer constituted of an alloy mainly composed of FePt to which at least one kind of non-magnetic material selected from a group constituted of C and an Si oxide is added.Type: ApplicationFiled: August 22, 2011Publication date: March 1, 2012Applicant: HITACHI, LTD.Inventors: Ikuko TAKEKUMA, Kimio NAKAMURA, Junichi SAYAMA, Hiroaki NEMOTO
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Patent number: 8000060Abstract: 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: GrantFiled: January 17, 2008Date of Patent: August 16, 2011Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Zhengang Zhang, Ikuko Takekuma, Kiwamu Tanahashi
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Patent number: 7701667Abstract: Embodiments in accordance with the present invention provide a perpendicular recording medium with low noise and high recording density by reducing the effects from noise generated from the vicinity of the interface with the intermediate layer of the recording layer, in a perpendicular recording medium utilizing a granular recording layer containing oxygen or oxide additive in a cobalt-chromium alloy formed on an intermediate layer with a ruthenium or ruthenium alloy layer. A first recording layer and a second recording layer are formed in order on an intermediate layer of ruthenium or ruthenium alloy. The first recording layer and the second recording layer are comprised of cobalt as the main material in a granular structure containing chromium and oxygen. The saturation magnetization of the first recording layer is lower than the saturation magnetization of the second recording layer.Type: GrantFiled: January 9, 2007Date of Patent: April 20, 2010Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Ichiro Tamai, Ikuko Takekuma, Hiroaki Nemoto, Yoshiyuki Hirayama
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Patent number: 7651795Abstract: 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: GrantFiled: September 14, 2005Date of Patent: January 26, 2010Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Ichiro Tamai, Ikuko Takekuma, Yoshiyuki Hirayama, Yuzuru Hosoe, Yoshinori Honda
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Patent number: 7641989Abstract: Embodiments of the invention provide a medium which provides high media S/N and good corrosion resistance. According to one embodiment, in a perpendicular magnetic recording medium at least comprising a soft-magnetic underlayer, a seed layer, an intermediate layer, a magnetic recording layer and an overcoat layer which are stacked over a substrate in order, the magnetic recording layer has a granular structure which consists of many columnar grains of CoCrPt alloy and a grain boundary layer containing an oxide, the seed layer is made of TaNi alloy or TaTi alloy and the intermediate layer is made of Ru or Ru alloy which contains about 80 at. % Ru or more.Type: GrantFiled: December 5, 2005Date of Patent: January 5, 2010Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Ikuko Takekuma, Reiko Arai, Yoko Ogawa, Yoshiyuki Hirayama, Yuzuru Hosoe, Tomio Iwasaki
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Patent number: 7625646Abstract: 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: GrantFiled: February 15, 2006Date of Patent: December 1, 2009Assignee: Hitachi Global Storage Technologies Japan, Ltd.Inventors: Yoshiyuki Hirayama, Ichiro Tamai, Takayuki Ichihara, Hiroyuki Nakagawa, Hiroaki Nemoto, Mineaki Kodama, Ikuko Takekuma
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Patent number: 7625644Abstract: In a granular magnetic recording layer of a perpendicular magnetic recording medium, media noises are reduced by separating adequately magnetic crystal grains and non-magnetic grain boundary and decreasing magnetic exchange interactions among the magnetic crystal grains without causing damage to magnetic anisotropy of the magnetic crystal grains. In one embodiment, the perpendicular magnetic recording medium, in which crystal alloy grains containing Co, Pt, and Cr, and non-magnetic grain boundary containing Si and O is included; the ratio of the number of O atom to that of Si atom in the magnetic recording layer is between about 2.5 and 5; the Si atomic composition in the magnetic recording layer is between about 3 and 6 atomic %; and the O atomic composition in the magnetic recording layer is between about 12 and 20 atomic %, is used. The in-plane distribution of perpendicular coercivity at any points of the medium of the magnetic recording layer is made at most about ±10% of an average value.Type: GrantFiled: October 24, 2005Date of Patent: December 1, 2009Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Takayuki Ichihara, Hiroyuki Nakagawa, Ikuko Takekuma, Ichiro Tamai
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Patent number: 7618722Abstract: 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: GrantFiled: March 27, 2008Date of Patent: November 17, 2009Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Yoshiyuki Hirayama, Ikuko Takekuma, Hiroyuki Nakagawa, Yuzuru Hosoe