Patents by Inventor Tadaaki Oikawa
Tadaaki 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).
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Publication number: 20190080833Abstract: According to one emcodiment, a magnetic device comprising a magnetoresistive effect element, wherein the magnetoresistive effect element; includes: a first ferromagnetic body, a second ferromagnetic body, and a first rare-earth ferromagnetic oxide that is provided between the first ferromagnetic body and the second ferromagnetic body and magnetically joins the first ferromagnetic body and the second ferromagnetic body.Type: ApplicationFiled: March 13, 2018Publication date: March 14, 2019Applicant: TOSHIBA MEMORY CORPORATIONInventors: Young Min EEH, Toshihiko NAGASE, Daisuke WATANABE, Kazuya SAWADA, Tadaaki OIKAWA, Kenichi YOSHINO
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Publication number: 20190080739Abstract: According to one embodiment, a magnetoresistive element includes: a first magnetic layer having a magnetization direction that is variable; a second magnetic layer having a magnetization direction that is invariable; a first non-magnetic layer provided between the first magnetic layer and the second magnetic layer; a third magnetic layer that fixes the magnetization direction of the second magnetic layer and that antiferromagnetically couples with the second magnetic layer; and a second non-magnetic layer provided between the second magnetic layer and the third magnetic layer. The second non-magnetic layer includes ruthenium (Ru) and a metal element.Type: ApplicationFiled: March 9, 2018Publication date: March 14, 2019Applicant: TOSHIBA MEMORY CORPORATIONInventors: Tadaaki OIKAWA, Young Min EEH, Kazuya SAWADA, Kenichi YOSHINO, Toshihiko NAGASE, Daisuke WATANABE
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Publication number: 20190019841Abstract: A semiconductor device includes a first rare earth oxide layer, a first magnetic layer adjacent to the first rare earth oxide layer, a second rare earth oxide layer, a second magnetic layer adjacent to the second rare earth oxide layer, and a nonmagnetic layer. The first magnetic layer is disposed between the first rare earth oxide layer and the nonmagnetic layer and is oriented in a crystal surface which is the same as a crystal surface of the nonmagnetic layer. The second magnetic layer is disposed between the second rare earth oxide layer and the nonmagnetic layer and is oriented in a crystal surface which is the same as a crystal surface of the nonmagnetic layer. The nonmagnetic layer is disposed between the first magnetic layer and the second magnetic layer.Type: ApplicationFiled: September 9, 2018Publication date: January 17, 2019Applicant: TOSHIBA MEMORY CORPORATIONInventors: Youngmin EEH, Toshihiko NAGASE, Daisuke WATANABE, Kazuya SAWADA, Kenichi YOSHINO, Tadaaki OIKAWA, Hiroyuki OHTORI
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Publication number: 20180277745Abstract: According to one embodiment, a magnetic memory device includes a magnetoresistive element, the magnetoresistive element including a first magnetic layer having a variable magnetization direction, a second magnetic layer having a fixed magnetization direction and a nonmagnetic layer provided between the first magnetic layer and the second magnetic layer. The first magnetic layer includes first and second sub-magnetic layers each containing at least iron (Fe) and boron (B), and a concentration of boron (B) contained in the first sub-magnetic layer is different from a concentration of boron (B) contained in the second sub-magnetic layer.Type: ApplicationFiled: September 12, 2017Publication date: September 27, 2018Applicants: TOSHIBA MEMORY CORPORATION, SK HYNIX INC.Inventors: Tadaaki OIKAWA, Toshihiko NAGASE, Youngmin EEH, Daisuke WATANABE, Kazuya SAWADA, Kenichi YOSHINO, Hiroyuki OHTORI, Yang Kon KIM, Ku Youl JUNG, Jong Koo LIM, Jae Hyoung LEE, Soo Man SEO, Sung Woong CHUNG, Tae Young LEE
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Publication number: 20180205006Abstract: A magnetoresistive memory device includes a first magnetic layer having a variable magnetization direction; a second magnetic layer, a magnetization direction of the second magnetic layer being invariable; a first nonmagnetic layer provided between the first magnetic layer and the second magnetic layer; and a second nonmagnetic layer provided on the first magnetic layer, which is opposite the first nonmagnetic layer. The first magnetic layer having a stacked layer structure in which amorphous magnetic material layer is sandwiched between crystalline magnetic material layers.Type: ApplicationFiled: March 12, 2018Publication date: July 19, 2018Applicant: TOSHIBA MEMORY CORPORATIONInventors: Daisuke WATANABE, Toshihiko NAGASE, Youngmin EEH, Kazuya SAWADA, Makoto NAGAMINE, Tadaaki OIKAWA, Kenichi YOSHINO, Hiroyuki OHTORI
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Patent number: 9947862Abstract: According to one embodiment, a magnetoresistive memory device includes a first magnetic layer in which a magnetization direction is variable, a first nonmagnetic layer provided on the first magnetic layer, a second magnetic layer provided on the first nonmagnetic layer, a magnetization direction of the second magnetic layer being invariable, and a second nonmagnetic layer provided on the first magnetic layer, which is opposite the first nonmagnetic layer. The first magnetic layer includes Mo.Type: GrantFiled: September 16, 2016Date of Patent: April 17, 2018Assignee: TOSHIBA MEMORY CORPORATIONInventors: Daisuke Watanabe, Toshihiko Nagase, Youngmin Eeh, Kazuya Sawada, Makoto Nagamine, Tadaaki Oikawa, Kenichi Yoshino, Hiroyuki Ohtori
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Publication number: 20180076262Abstract: According to one embodiment, a semiconductor device includes a first rare earth oxide layer, a first magnetic layer being adjacent to the first rare earth oxide layer, and a nonmagnetic layer, the first magnetic layer being disposed between the first rare earth oxide layer and the nonmagnetic layer and being oriented in a crystal surface which is the same as a crystal surface of the nonmagnetic layer.Type: ApplicationFiled: February 28, 2017Publication date: March 15, 2018Applicant: TOSHIBA MEMORY CORPORATIONInventors: Youngmin EEH, Toshihiko NAGASE, Daisuke WATANABE, Kazuya SAWADA, Kenichi YOSHINO, Tadaaki OIKAWA, Hiroyuki OHTORI
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Publication number: 20180076383Abstract: According to one embodiment, a magnetic memory device includes a first magnetic layer having a variable magnetization direction, a second magnetic layer having a fixed magnetization direction, and a nonmagnetic layer between the first and second magnetic layers. The second magnetic layer includes a first main surface on the nonmagnetic layer side and a second main surface opposite to the first main surface, and includes a first region on the first main surface side and a second region on the second main surface side, and an intermediate region between the first and second regions and containing a predetermined nonmagnetic element. A concentration of the predetermined nonmagnetic element in the intermediate region is higher than that in the first and second regions. The second magnetic layer contains a magnetic element from the first to second main surfaces.Type: ApplicationFiled: March 20, 2017Publication date: March 15, 2018Applicant: TOSHIBA MEMORY CORPORATIONInventors: Kazuya SAWADA, Toshihiko NAGASE, Youngmin EEH, Daisuke WATANABE, Kenichi YOSHINO, Tadaaki OIKAWA, Hiroyuki OHTORI
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Publication number: 20170263858Abstract: According to one embodiment, a magnetic memory device includes a stacked structure including a first magnetic layer, a second magnetic layer and a nonmagnetic layer between the first magnetic layer and the second magnetic layer, and a sidewall insulating layer provided on a side surface of the stacked structure and containing boron (B).Type: ApplicationFiled: September 16, 2016Publication date: September 14, 2017Applicant: KABUSHIKI KAISHA TOSHIBAInventors: Yasuyuki SONODA, Daisuke WATANABE, Masatoshi YOSHIKAWA, Youngmin EEH, Shuichi TSUBATA, Toshihiko NAGASE, Yutaka HASHIMOTO, Kazuya SAWADA, Kazuhiro TOMIOKA, Kenichi YOSHINO, Tadaaki OIKAWA
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Publication number: 20170263857Abstract: According to one embodiment, a magnetoresistive memory device includes a first magnetic layer in which a magnetization direction is variable, a first nonmagnetic layer provided on the first magnetic layer, a second magnetic layer provided on the first nonmagnetic layer, a magnetization direction of the second magnetic layer being invariable, and a second nonmagnetic layer provided on the first magnetic layer, which is opposite the first nonmagnetic layer. The first magnetic layer includes Mo.Type: ApplicationFiled: September 16, 2016Publication date: September 14, 2017Applicant: KABUSHIKI KAISHA TOSHIBAInventors: Daisuke WATANABE, Toshihiko NAGASE, Youngmin EEH, Kazuya SAWADA, Makoto NAGAMINE, Tadaaki OIKAWA, Kenichi YOSHINO, Hiroyuki OHTORI
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Patent number: 9418780Abstract: A magnetic composite material including a dielectric material and magnetic metal particles in the dielectric material, wherein and a real part ?? of a complex permeability is greater than about 1 at a frequency of about 3 gigahertz (GHz), and the loss tangent tan ? is less than or equal to about 0.1.Type: GrantFiled: December 6, 2013Date of Patent: August 16, 2016Assignee: SAMSUNG ELECTRONICS CO., LTD.Inventors: Tadaaki Oikawa, Kotaro Hata
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Publication number: 20140158929Abstract: A magnetic composite material including a dielectric material and magnetic metal particles in the dielectric material, wherein and a real part ?? of a complex permeability is greater than about 1 at a frequency of about 3 gigahertz (GHz), and the loss tangent tan ? is less than or equal to about 0.1.Type: ApplicationFiled: December 6, 2013Publication date: June 12, 2014Applicant: SAMSUNG ELECTRONICS CO., LTD.Inventors: Tadaaki Oikawa, Kotaro Hata
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Patent number: 8691402Abstract: A perpendicular magnetic recording medium according to which both the thermal stability of the magnetization is good and writing with a magnetic head is easy, and moreover the SNR is improved. In the case of a perpendicular magnetic recording medium comprising a nonmagnetic substrate (1), and at least a nonmagnetic underlayer (2), a magnetic recording layer (3), and a protective layer (4) formed in this order on the nonmagnetic substrate (1), the magnetic recording layer (3) comprises a low Ku region (31) layer having a perpendicular magnetic anisotropy constant (Ku value) of not more than 1×105 erg/cm3, and a high Ku region (32) layer having a Ku value of at least 1×106 erg/cm3. Moreover, the magnetic recording layer (3) is made to have therein nonmagnetic grain boundaries that contain a nonmagnetic oxide and magnetically isolate crystal grains, which are made of a ferromagnetic metal, from one another.Type: GrantFiled: November 2, 2012Date of Patent: April 8, 2014Assignees: Fuji Electric Co., Ltd., National University Corporation Tohoku UniversityInventors: Osamu Kitakami, Yutaka Shimada, Satoshi Okamoto, Takehito Shimatsu, Hajime Aoi, Hiroaki Muraoka, Yoshihisa Nakamura, Hiroyuki Uwazumi, Tadaaki Oikawa
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Patent number: 8323808Abstract: There is provided a perpendicular magnetic recording medium according to which both the thermal stability of the magnetization is good and writing with a magnetic head is easy, and moreover the SNR is improved. In the case of a perpendicular magnetic recording medium comprising a nonmagnetic substrate 1, and at least a nonmagnetic underlayer 2, a magnetic recording layer 3 and a protective layer 4 formed in this order on the nonmagnetic substrate 1, the magnetic recording layer 3 comprises a low Ku region 31 layer having a perpendicular magnetic anisotropy constant (Ku value) of not more than 1×105 erg/cm3, and a high Ku region 32 layer having a Ku value of at least 1×106 erg/cm3. Moreover, the magnetic recording layer 3 is made to have therein nonmagnetic grain boundaries that contain a nonmagnetic oxide and magnetically isolate crystal grains, which are made of a ferromagnetic metal, from one another.Type: GrantFiled: January 10, 2005Date of Patent: December 4, 2012Assignees: Fuji Electric Co., Ltd., National University Corporation Tohoku UniversityInventors: Osamu Kitakami, Yutaka Shimada, Satoshi Okamoto, Takehito Shimatsu, Hajime Aoi, Hiroaki Muraoka, Yoshihisa Nakamura, Hiroyuki Uwazumi, Tadaaki Oikawa
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Patent number: 8252152Abstract: The quantity of oxide contained in a magnetic layer is controlled to control the crystal grains and the segregation structure for ensuring low noise characteristic in a granular magnetic layer of a perpendicular magnetic recording medium. The granular magnetic layer consists of ferromagnetic crystal grains and a nonmagnetic grain boundary region mainly of an oxide surrounding the ferromagnetic crystal grains. The perpendicular magnetic recording medium has a nonmagnetic underlayer composed of a metal or alloy having hexagonal closest-packed crystal structure. The ferromagnetic crystal grain is composed of an alloy containing at least cobalt and platinum. The volume proportion of the nonmagnetic grain boundary region mainly of the oxide falls within a range of 15% to 40% of the volume of the total magnetic layer.Type: GrantFiled: October 3, 2008Date of Patent: August 28, 2012Assignee: Fuji Electric Co., Ltd.Inventors: Hiroyuki Uwazumi, Yasushi Sakai, Tadaaki Oikawa, Miyabi Nakamura
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Patent number: 8039133Abstract: A magnetic recording medium, and method of manufacturing the same, is provided with excellent recording performance by employing a granular magnetic layer having a specified composition. A magnetic recording medium according to the present invention comprises a nonmagnetic underlayer, a granular magnetic layer, a protective film, and a liquid lubrication layer sequentially laminated on a nonmagnetic substrate. The granular magnetic layer consists of ferromagnetic crystal grains containing cobalt and nonmagnetic grain boundary region surrounding the ferromagnetic crystal grains. The ferromagnetic crystal grains contain platinum in the range of 15 at % to 17 at %.Type: GrantFiled: April 26, 2005Date of Patent: October 18, 2011Assignee: Fuji Electric Device Technology Co., Ltd.Inventors: Miyabi Nakamura, Takahiro Shimizu, Hiroyuki Uwazumi, Naoki Takizawa, Tadaaki Oikawa
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Patent number: 8034470Abstract: A perpendicular magnetic recording medium is disclosed in which a soft magnetic layer used as a low Ku layer can be stably produced with high performance. Thermal stabilization of magnetization, ease of writing by a magnetic head, and SNR also are improved. A method of manufacturing the medium is disclosed. The perpendicular magnetic recording medium includes at least a nonmagnetic underlayer, a magnetic recording layer, and a protective layer formed in this order on a nonmagnetic substrate. The magnetic recording layer includes a low Ku layer having a relatively small perpendicular magnetic anisotropy constant (Ku value), and a high Ku layer in which the Ku value is relatively large, and the low Ku layer includes a soft magnetic thin film including an iron group element-based microcrystal structure, in which a nitrogen element is added to a ferromagnetic material mainly containing one of metals of Co, Ni and Fe or an alloy of the metal.Type: GrantFiled: March 14, 2008Date of Patent: October 11, 2011Assignee: Fuji Electric Co., Ltd.Inventors: Tadaaki Oikawa, Hiroyuki Uwazumi
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Publication number: 20090026066Abstract: The quantity of oxide contained in a magnetic layer is controlled to control the crystal grains and the segregation structure for ensuring low noise characteristic in a granular magnetic layer of a perpendicular magnetic recording medium. The granular magnetic layer consists of ferromagnetic crystal grains and a nonmagnetic grain boundary region mainly of an oxide surrounding the ferromagnetic crystal grains. The perpendicular magnetic recording medium has a nonmagnetic underlayer composed of a metal or alloy having hexagonal closest-packed crystal structure. The ferromagnetic crystal grain is composed of an alloy containing at least cobalt and platinum. The volume proportion of the nonmagnetic grain boundary region mainly of the oxide falls within a range of 15% to 40% of the volume of the total magnetic layer.Type: ApplicationFiled: October 3, 2008Publication date: January 29, 2009Applicant: FUJI ELECTRIC DEVICE TECHNOLOGY CO., LTD.Inventors: Hiroyuki UWAZUMI, Yasushi SAKAI, Tadaaki OIKAWA, Miyabi NAKAMURA
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Publication number: 20080226950Abstract: A perpendicular magnetic recording medium is disclosed in which a soft magnetic layer used as a low Ku layer can be stably produced with high performance. Thermal stabilization of magnetization, ease of writing by a magnetic head, and SNR also are improved. A method of manufacturing the medium is disclosed. The perpendicular magnetic recording medium includes at least a nonmagnetic underlayer, a magnetic recording layer, and a protective layer formed in this order on a nonmagnetic substrate. The magnetic recording layer includes a low Ku layer having a relatively small perpendicular magnetic anisotropy constant (Ku value), and a high Ku layer in which the Ku value is relatively large, and the low Ku layer includes a soft magnetic thin film including an iron group element-based microcrystal structure, in which a nitrogen element is added to a ferromagnetic material mainly containing one of metals of Co, Ni and Fe or an alloy of the metal.Type: ApplicationFiled: March 14, 2008Publication date: September 18, 2008Applicant: FUJI ELECTRIC DEVICE TECHNOLOGY CO., LTD.Inventors: Tadaaki OIKAWA, Hiroyuki UWAZUMI
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Patent number: RE41282Abstract: A perpendicular magnetic recording medium has a granular magnetic layer and a nonmagnetic underlayer of a metal or an alloy having a hexagonal close packed (hcp) crystal structure. A seed layer of a metal or an alloy of a face-centered cubic (fcc) crystal structure is provided under the nonmagnetic underlayer. Such a perpendicular magnetic recording medium exhibits excellent magnetic characteristics even when the thickness of the underlayer or the total thickness of the underlayer and the seed layer is very thin. Excellent magnetic characteristics can be obtained even when of the substrate is not preheated. Accordingly, a nonmagnetic substrate, such as a plastic resin can be employed to reduce the manufacturing cost.Type: GrantFiled: November 27, 2007Date of Patent: April 27, 2010Assignee: Fuji Electric Device Technology Co., Ltd.Inventors: Hiroyuki Uwazumi, Yasushi Sakai, Tadaaki Oikawa, Miyabi Nakamura