Patents by Inventor Masatoshi Yoshikawa

Masatoshi Yoshikawa 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: 20090034134
    Abstract: A magnetoresistance effect element includes a magnetoresistance effect film including a magnetically pinned layer having a magnetic material film whose direction of magnetization is pinned substantially in one direction, a magnetically free layer having a magnetic material film whose direction of magnetization changes in response to an external magnetic field, and a nonmagnetic metal intermediate layer located between said pinned layer and said free layer. The element also includes a pair of electrodes electrically connected to the magnetoresistance effect film to supply a sense current perpendicularly to a film plane of the magnetoresistance effect film. At least one of the pinned layer and the free layer may include a thin-film insertion layer.
    Type: Application
    Filed: September 23, 2008
    Publication date: February 5, 2009
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Hiromi Yuasa, Yuzo Kamiguchi, Masatoshi Yoshikawa, Katsuhiko Koul, Hitoshi Iwasaki, Tomohiko Nagata, Takeo Sakakubo, Masashi Sahashi
  • Publication number: 20090021869
    Abstract: There is provided a practical magnetoresistance effect element which has an appropriate value of resistance, which can be sensitized and which has a small number of magnetic layers to be controlled, and a magnetic head and magnetic recording and/or reproducing system using the same. In a magnetoresistance effect element wherein a sense current is caused to flow in a direction perpendicular to the plane of the film, a resistance regulating layer is provided in at least one of a pinned layer, a free layer and an non-magnetic intermediate layer. The resistance regulating layer contains, as a principal component, an oxide, a nitride, a fluoride, a carbide or a boride. The resistance regulating layer may be a continuous film or may have pin holes. Thus, it is possible to provide a practical magnetoresistance effect element which has an appropriate value of resistance, which can be sensitized and which has a small number of magnetic layers, while effectively utilizing the scattering effect depending on spin.
    Type: Application
    Filed: September 17, 2008
    Publication date: January 22, 2009
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Yuuzo KAMIGUCHI, Hiromi YUASA, Tomohiko NAGATA, Hiroaki YODA, Katsuhiko KOUI, Masatoshi YOSHIKAWA, Hitoshi IWASAKI, Masashi SAHASHI, Masayuki TAKAGISHI
  • Patent number: 7463456
    Abstract: A spin valve type magnetoresistive effect element for vertical electric conduction includes a magnetoresistive effect film in which a resistance adjustment layer made of a material containing conductive carriers not more than 1022/cm3 is inserted. Thus the resistance value of a portion in change of spin-relied conduction is raised to an adequate valve, thereby to increase the resistance variable amount.
    Type: Grant
    Filed: April 9, 2007
    Date of Patent: December 9, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Hiromi Yuasa, Masatoshi Yoshikawa, Katsuhiko Koui, Hitoshi Iwasaki, Masashi Sahashi
  • Publication number: 20080291585
    Abstract: It is made possible to provide a magnetoresistive effect element that can reverse magnetization direction with a low current, having low areal resistance (RA) and a high TMR ratio. A magnetoresistive effect element includes: a film stack that includes a magnetization free layer including a magnetic layer in which magnetization direction is changeable, a magnetization pinned layer including a magnetic layer in which magnetization direction is pinned, and an intermediate layer provided between the magnetization free layer and the magnetization pinned layer, the intermediate layer being an oxide containing boron (B) and an element selected from the group consisting of Ca, Mg, Sr, Ba, Ti, and Sc. Current is applied bidirectionally between the magnetization pinned layer and the magnetization free layer through the intermediate layer, so that the magnetization of the magnetization free layer is reversible.
    Type: Application
    Filed: August 23, 2007
    Publication date: November 27, 2008
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Masatoshi Yoshikawa, Tadashi Kai, Toshihiko Nagase, Eiji Kitagawa, Tatsuya Kishi, Hiroaki Yoda
  • Patent number: 7443004
    Abstract: In a spin valve type element, an interface insertion layer (32, 34) of a material exhibiting large spin-dependent interface scattering is inserted in a location of a magnetically pinned layer (16) or a magnetically free layer (20) closer to a nonmagnetic intermediate layer (18). A nonmagnetic back layer (36) may be additionally inserted as an interface not in contact with the nonmagnetic intermediate layer to increase the output by making use of spin-dependent interface scattering along the interface between the pinned layer and the nonmagnetic back layer or between the free layer and the nonmagnetic back layer.
    Type: Grant
    Filed: November 22, 2005
    Date of Patent: October 28, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Hiromi Yuasa, Yuzo Kamiguchi, Masatoshi Yoshikawa, Katsuhiko Koui, Hitoshi Iwasaki, Tomohiko Nagata, Takeo Sakakubo, Masashi Sahashi
  • Publication number: 20080253174
    Abstract: A magnetoresistive effect element includes a first magnetic layer, a second magnetic layer, and a first spacer layer. The first magnetic layer has an invariable magnetization direction. The second magnetic layer has a variable magnetization direction, and contains at least one element selected from Fe, Co, and Ni, at least one element selected from Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, and Au, and at least one element selected from V, Cr, and Mn. The spacer layer is formed between the first magnetic layer and the second magnetic layer, and made of a nonmagnetic material. A bidirectional electric current flowing through the first magnetic layer, the spacer layer, and the second magnetic layer makes the magnetization direction of the second magnetic layer variable.
    Type: Application
    Filed: March 13, 2008
    Publication date: October 16, 2008
    Inventors: Masatoshi YOSHIKAWA, Eiji Kitagawa, Tadashi Kai, Toshihiko Nagase, Tatsuya Kishi, Hiroaki Yoda
  • Publication number: 20080231998
    Abstract: A magnetoresistive effect element includes a magnetization fixed layer having substantially fixed magnetization direction. A magnetization variable layer has a variable magnetization direction, consists of a magnetic alloy that has a BCC structure and is expressed by Fe1-x-yCoxNiy (0?x+y?1, 0?x?1, 0?y?1), and contains at least one additive element of V, Cr, and Mn in a range of 0<a?20 at % (a is a content). An intermediate layer is disposed between the magnetization fixed layer and the magnetization variable layer and consists of a nonmagnetic material. The magnetization direction of the magnetization variable layer is switched by a bidirectional current passing through the magnetization fixed layer, the intermediate layer, and the magnetization variable layer.
    Type: Application
    Filed: September 20, 2007
    Publication date: September 25, 2008
    Inventors: Masatoshi YOSHIKAWA, Tadashi Kai, Toshihiko Nagase, Eiji Kitagawa, Tatsuya Kishi, Hiroaki Yoda
  • Publication number: 20080180859
    Abstract: A magnetoresistive element includes: a magnetization free layer having a first plane and a second plane located on the opposite side from the first plane, and having a variable magnetization direction; a magnetization pinned layer provided on the first plane side of the magnetization free layer, and having a pinned magnetization direction; a first tunnel barrier layer provided between the magnetization free layer and the magnetization pinned layer; a second tunnel barrier layer provided on the second plane of the magnetization free layer; and a non-magnetic layer provided on a plane on the opposite side of the second tunnel barrier layer from the magnetization free layer. The magnetization direction of the magnetization free layer is variable by applying current between the magnetization pinned layer and the non-magnetic layer, and a resistance ratio between the first tunnel barrier layer and the second tunnel barrier layer is in a range of 1:0.25 to 1:4.
    Type: Application
    Filed: January 15, 2008
    Publication date: July 31, 2008
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Tomomasa UEDA, Hisanori AIKAWA, Masatoshi YOSHIKAWA, Naoharu SHIMOMURA, Masahiko NAKAYAMA, Sumio IKEGAWA, Keiji HOSOTANI, Makoto NAGAMINE
  • Patent number: 7379278
    Abstract: A magnetoresistance effect element comprises a magnetoresistance effect film including a magnetically pinned layer whose direction of magnetization is pinned substantially in one direction, a magnetically free layer whose direction of magnetization changes in response to an external magnetic field, and a nonmagnetic intermediate layer located between the pinned layer and the free layer; and a pair of electrodes electrically connected to said magnetoresistance effect film to supply a sense current perpendicularly to a film plane of said magnetoresistance effect film, The intermediate layer has a first layer including a first region whose resistance is relatively high and second regions whose resistance is relatively low. The sense current preferentially flows through the second regions when the current passes the first layer.
    Type: Grant
    Filed: April 7, 2006
    Date of Patent: May 27, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Katsuhiko Koui, Masatoshi Yoshikawa, Masayuki Takagishi, Masashi Sahashi, Takeo Sakakubo, Hitoshi Iwasaki
  • Patent number: 7375405
    Abstract: A magnetoresistance effect (MR) device incorporating a spin valve film, and a magnetic head, a magnetic head assembly and a magnetic recording/reproducing system incorporating the MR device, wherein the magnetization direction of a free layer is at a certain angle to the magnetization direction of a second ferromagnetic layer therein when the applied magnetic field is zero. A pinned magnetic layer includes a pair of ferromagnetic films antiferromagnetically coupled to each other via a coupling film existing therebetween. The magnetization direction of either one of the pair of ferromagnetic films constituting the pinned magnetic layer is maintained, and a nonmagnetic high-conductivity layer is disposed adjacent to a first ferromagnetic layer on the side opposite to the side on which the first ferromagnetic layer is contacted with a nonmagnetic spacer layer. With that constitution, the device has extremely high sensitivity, and the bias point in the device is well controlled.
    Type: Grant
    Filed: March 15, 2005
    Date of Patent: May 20, 2008
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Hideaki Fukuzawa, Yuzo Kamiguchi, Katsuhiko Koui, Shin-ichi Nakamura, Hitoshi Iwasaki, Kazuhiro Saito, Hiromi Fuke, Masatoshi Yoshikawa, Susumu Hashimoto, Masashi Sahashi
  • Publication number: 20080088980
    Abstract: A magnetoresistive element includes a free layer which contains a magnetic material and has an fct crystal structure with a (001) plane oriented, the free layer having a magnetization which is perpendicular to a film plane and has a direction to be changeable by spin-polarized electrons, a first nonmagnetic layer and a second nonmagnetic layer which sandwich the free layer and have one of a tetragonal crystal structure and a cubic crystal structure, and a fixed layer which is provided on only one side of the free layer and on a surface of the first nonmagnetic layer opposite to a surface with the free layer and contains a magnetic material, the fixed layer having a magnetization which is perpendicular to a film plane and has a fixed direction.
    Type: Application
    Filed: August 1, 2007
    Publication date: April 17, 2008
    Inventors: Eiji KITAGAWA, Toshihiko Nagase, Masatoshi Yoshikawa, Katsuya Nishiyama, Tatsuya Kishi, Hiroaki Yoda
  • Publication number: 20080068765
    Abstract: A spin valve type magnetoresistive effect element for vertical electric conduction includes a magnetoresistive effect film in which a resistance adjustment layer made of a material containing conductive carriers not more than 1022/cm3 is inserted. Thus the resistance value of a portion in change of spin-relied conduction is raised to an adequate value, thereby to increase the resistance variable amount.
    Type: Application
    Filed: October 31, 2007
    Publication date: March 20, 2008
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Hiromi Yuasa, Masatoshi Yoshikawa, Katsuhiko Koui, Hitoshi Iwasaki, Masashi Sahashi
  • Publication number: 20080043519
    Abstract: An inadvertent write can be prevented when a read is performed. The duration of the write current pulse for writing information in the magnetic memory layer is longer than the duration of the read current pulse for reading the information from the magnetic memory layer.
    Type: Application
    Filed: July 27, 2007
    Publication date: February 21, 2008
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Eiji KITAGAWA, Masatoshi Yoshikawa, Tatsuya Kishi, Hiroaki Yoda
  • Publication number: 20070297220
    Abstract: A magnetoresistive includes a first magnetic reference layer having a fixed magnetization direction, a magnetic free layer having a magnetization direction which is changeable by being supplied with spin polarized electrons, a second magnetic reference layer having a fixed magnetization direction, a first intermediate layer provided between the first magnetic reference layer and the magnetic free layer, and a second intermediate layer provided between the magnetic free layer and the second magnetic reference layer. The magnetic free layer and the first magnetic reference layer have directions of easy magnetization perpendicular or parallel to an in-plane direction. The first magnetic reference layer and the second magnetic reference layer have directions of easy magnetization perpendicular to each other.
    Type: Application
    Filed: January 23, 2007
    Publication date: December 27, 2007
    Inventors: Masatoshi YOSHIKAWA, Tadashi Kai, Toshihiko Nagase, Tatsuya Kishi, Hiroaki Yoda
  • Publication number: 20070177310
    Abstract: A spin valve type magnetoresistive effect element for vertical electric conduction includes a magnetoresistive effect film in which a resistance adjustment layer made of a material containing conductive carriers not more than 1022/cm3 is inserted. Thus the resistance value of a portion in change of spin-relied conduction is raised to an adequate valve, thereby to increase the resistance variable amount.
    Type: Application
    Filed: April 9, 2007
    Publication date: August 2, 2007
    Applicant: KABUSHIKI KAISHA TOSHIBA
    Inventors: Hiromi YUASA, Masatoshi Yoshikawa, Katsuhiko Koui, Hitoshi Iwasaki, Masashi Sahashi
  • Patent number: 7248448
    Abstract: Disclosed are a high-sensitivity and high-reliability magnetoresistance effect device (MR device) in which bias point designing is easy, and also a magnetic head, a magnetic head assembly and a magnetic recording/reproducing system incorporating the MR device. In the MR device incorporating a spin valve film, the magnetization direction of the free layer is at a certain angle to the magnetization direction of a second ferromagnetic layer therein when the applied magnetic field is zero. In this, the pinned magnetic layer comprises a pair of ferromagnetic films as antiferromagnetically coupled to each other via a coupling film existing therebetween.
    Type: Grant
    Filed: September 10, 2004
    Date of Patent: July 24, 2007
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Hideaki Fukuzawa, Yuzo Kamiguchi, Katsuhiko Koui, Shin-ichi Nakamura, Hitoshi Iwasaki, Kazuhiro Saito, Hiromi Fuke, Masatoshi Yoshikawa, Susumu Hashimoto, Masashi Sahashi
  • Publication number: 20070154740
    Abstract: A magnetoresistive device includes a magnetization pinned layer, a magnetization free layer, a nonmagnetic intermediate layer formed between the magnetization pinned layer and the magnetization free layer, and electrodes allowing a sense current to flow in a direction substantially perpendicular to the plane of the stack including the magnetization pinned layer, the nonmagnetic intermediate layer and the magnetization free layer. At least one of the magnetization pinned layer and the magnetization free layer is substantially formed of a binary or ternary alloy represented by the formula FeaCobNic (where a+b+c=100 at %, and a?75 at %, b?75 at %, and c?63 at %), or formed of an alloy having a body-centered cubic crystal structure.
    Type: Application
    Filed: March 13, 2007
    Publication date: July 5, 2007
    Inventors: Hiromi Yuasa, Masatoshi Yoshikawa, Yuzo Kamiguchi, Hitoshi Iwasaki, Masashi Sahashi
  • Patent number: 7223485
    Abstract: A magnetoresistive device includes a magnetization pinned layer, a magnetization free layer, a nonmagnetic intermediate layer formed between the magnetization pinned layer and the magnetization free layer, and electrodes allowing a sense current to flow in a direction substantially perpendicular to the plane of the stack including the magnetization pinned layer, the nonmagnetic intermediate layer and the magnetization free layer. At least one of the magnetization pinned layer and the magnetization free layer is substantially formed of a binary or ternary alloy represented by the formula FeaCobNic (where a+b+c=100 at %, and a?75 at %, b?75 at %, and c?63 at %), or formed of an alloy having a body-centered cubic crystal structure.
    Type: Grant
    Filed: March 7, 2005
    Date of Patent: May 29, 2007
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Hiromi Yuasa, Masatoshi Yoshikawa, Yuzo Kamiguchi, Hitoshi Iwasaki, Masashi Sahashi
  • Patent number: 7218483
    Abstract: A spin valve type magnetoresistive effect element for vertical electric conduction includes a magnetoresistive effect film in which a resistance adjustment layer made of a material containing conductive carriers not more than 1022/cm3 is inserted. Thus the resistance value of a portion in change of spin-relied conduction is raised to an adequate value, thereby to increase the resistance variable amount.
    Type: Grant
    Filed: June 21, 2002
    Date of Patent: May 15, 2007
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Hiromi Yuasa, Masatoshi Yoshikawa, Katsuhiko Koui, Hitoshi Iwasaki, Masashi Sahashi
  • Patent number: 7215516
    Abstract: A magnetoresistive head includes a first magnetic shield, a first insulating film, a magnetoresistive film, a second insulating film and a second magnetic shield arranged in a track direction. The magnetoresistive film includes a magnetization free layer adjacent to an air-bearing surface, a magnetization pinned layer spaced apart from the magnetization free layer in a head height direction as viewed from the air-bearing surface, and a nonmagnetic intermediate layer connecting the magnetization free layer and the magnetization pinned layer, a magnetization direction of the magnetization free layer being rotatable in an external magnetic field and a magnetization direction of the magnetization pinned layer being substantially pinned under the external magnetic field.
    Type: Grant
    Filed: February 26, 2004
    Date of Patent: May 8, 2007
    Assignee: Kabushiki Kaisha Toshiba
    Inventors: Masatoshi Yoshikawa, Masayuki Takagishi