Patents by Inventor Masafumi Nakada

Masafumi Nakada 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: 6493195
    Abstract: A magnetoresistance element includes a lower electrode layer, a magnetoresistance effect layer, an upper electrode layer and a lower electrode anti-erosion/flaking layer. The lower electrode anti-erosion/flaking layer, which is formed before a photoresist layer remaining on the patterned lower electrode layer is removed, is formed around the lower electrode layer so that its edge facing the lower electrode layer will be in contact with the edge of the lower electrode layer.
    Type: Grant
    Filed: August 30, 2000
    Date of Patent: December 10, 2002
    Assignee: NEC Corporation
    Inventors: Kazuhiko Hayashi, Keishi Ohashi, Nobuyuki Ishiwata, Masafumi Nakada, Eizo Fukami, Hiroaki Honjo, Hisanao Tsuge, Atsushi Kamijo
  • Patent number: 6490139
    Abstract: A magneto-resistive element comprises a first electrode, a magneto-resistive layer formed on the first electrode in which resistance is changed in accordance with magnetic field, and a second electrode layer formed on the magneto-resistive layer. The magneto-resistive layer has a first magnetic layer formed on the first electrode, a non-magnetic layer formed on the first magnetic layer, and a second magnetic layer formed on the non-magnetic layer. The average surface roughness of the first electrode is equal to or smaller than 0.3 nm. Since the first electrode has such the small average surface roughness, the non-magnetic layer formed on the first electrode layer is flattened, thus, current leakage is prevented. The first electrode is made of at least one of Ta, Zr, Ti, Hf, W, Mo, Y, V, Nb, Au, Ag, Pd, and Pt which has strong bond strength. Since the first electrode has strong bond strength, exfoliation of the first electrode from the layers contacting the first electrode does not occur.
    Type: Grant
    Filed: January 27, 2000
    Date of Patent: December 3, 2002
    Assignee: NEC Corporation
    Inventors: Kazuhiko Hayashi, Keishi Ohashi, Nobuyuki Ishiwata, Masafumi Nakada, Hisao Matsutera, Hisanao Tsuge, Atsushi Kamijo
  • Patent number: 6452762
    Abstract: The present invention provides a magneto-resistive (MR) element comprising: a first magnetic layer 1 provided on a substrate; a non-magnetic layer 3 arranged to be in contact with the first magnetic layer; and a second magnetic layer 2 arranged to be in contact with the non-magnetic layer; wherein sense current flowing in the first and the second magnetic layer is changed by a resistance change according to an external magnetic field, and a sense current flowing distance in the first magnetic layer and/or a sense current flowing distance in the second magnetic layer is longer than a sense current flowing distance in a superimposed portion of the first magnetic layer, the non-magnetic layer, and the second magnetic layer.
    Type: Grant
    Filed: March 27, 2000
    Date of Patent: September 17, 2002
    Assignee: NEC Corporation
    Inventors: Kazuhiko Hayashi, Masafumi Nakada
  • Publication number: 20020097540
    Abstract: A magneto-resistance effect head is provided with a lower conductive layer which is provided with a recessed portion, and a vertical bias layer is provided in the recessed portion. A free layer is provided on the lower conductive layer. On the free layer, layered in the following order are the non-magnetic layer, the fixed layer, the fixing layer, and the upper layer so as not to be placed immediately above the vertical bias layer. The non-magnetic layer, the fixed layer, the fixing layer, and the upper layer are buried in an insulation layer. Furthermore, an upper conductive layer is provided on the upper layer and the insulation layer. In the direction of the magnetic field applied by the vertical bias layer, the free layer is made greater in length than the fixed layer and the free layer is disposed in proximity to the vertical bias layer with the distance between the fixed layer and the vertical bias layer remaining unchanged.
    Type: Application
    Filed: July 30, 2001
    Publication date: July 25, 2002
    Inventors: Kazuhiko Hayashi, Junichi Fujikata, Tsutomu Ishi, Shigeru Mori, Keishi Ohashi, Masafumi Nakada, Kiyokazu Nagahara, Kunihiko Ishihara, Nobuyuki Ishiwata
  • Publication number: 20020027753
    Abstract: A magneto-resistance effect (“MR”) type composite head includes a reproduction head with an MR element arranged between a first and a second magnetic shield; and a recording head arranged adjacent to the reproduction head so as to use the second magnetic shield as a first magnetic pole film and having a second magnetic pole film opposing to the first magnetic pole via a magnetic gap; the MR element includes a center region including a ferromagnetic tunnel junction magneto-resistance effect film having a first ferromagnetic layer and a second ferromagnetic layer for generating a magneto-resistance effect using the first and the second magnetic shields as electrodes so that a current flows in an almost vertical direction between the first and the second magnetic shields; a tunnel barrier layer provided between the first and the second ferromagnetic layer; and an end region arranged to sandwich the center region from both sides for /applying a bias magnetic field to the center region.
    Type: Application
    Filed: October 24, 2001
    Publication date: March 7, 2002
    Applicant: NEC Corporation
    Inventors: Nobuyuki Ishiwata, Hisanao Tsuge, Hisao Matsutera, Yuji Tsukamoto, Masafumi Nakada, Atsushi Kamijo
  • Publication number: 20020008016
    Abstract: A magnetoresistive effect sensor uses a shielded-type magnetoresistive effect element using a magnetoresistive effect film formed by a basic configuration of a combination of a free layer, a barrier layer formed on the free layer, and a fixed layer formed on the barrier layer, wherein a sensing current flows substantially perpendicular to the magnetoresistive effect film, and wherein an amorphous material or a microcrystalline material is used in a lower shield.
    Type: Application
    Filed: May 14, 2001
    Publication date: January 24, 2002
    Inventors: Kazuhiko Hayashi, Keishi Ohashi, Nobuyuki Ishiwata, Masafumi Nakada, Eizo Fukami, Kiyokazu Nagahara, Hiroaki Honjo, Junichi Fujikata, Kunihiko Ishihara, Shigeru Mori
  • Patent number: 6341053
    Abstract: The present invention provides a magnetic tunnel junction device for an external magnetic field sensor. The device comprises a stack of multi-layers, which include a first antiferromagnetic pinning layer, a ferromagnetic free layer, a tunneling barrier layer, a ferromagnetic pinned layer, and a second antiferromagnetic pinning layer. The first pinning layer has a first pinning field, which pins a magnetization of the free layer in a track width direction. The second pinning layer has a second pinning field, which pins a magnetization of the pinned layer in a direction in the plane of the stacked layers of the magnetic tunnel junction, along the applied external magnetic field direction.
    Type: Grant
    Filed: October 30, 1998
    Date of Patent: January 22, 2002
    Assignee: NEC Corporation
    Inventors: Masafumi Nakada, Hisanao Tsuge, Yuji Tsukamoto, Hisao Matsutera, Nobuyuki Ishiwata, Atsushi Kamijo
  • Patent number: 6333842
    Abstract: The present invention provides a magneto-resistance effect (hereinafter, referred to as MR) type composite head.
    Type: Grant
    Filed: December 3, 1998
    Date of Patent: December 25, 2001
    Assignee: NEC Corporation
    Inventors: Ishiwata Nobuyuki, Hisanao Tsuge, Hisao Matsutera, Yuji Tsukamoto, Masafumi Nakada, Atsushi Kamijo
  • Patent number: 6301088
    Abstract: The present invention provides a multilayer structure comprising: one of a first antiferromagnetic layer and a bias ferromagnetic layer; an interface control layer in contact with the one of the first antiferromagnetic layer and the bias ferromagnetic layer; a free magnetic layer in contact with the interface control layer; a non-magnetic layer in contact with the free magnetic layer; a pinned magnetic layer in contact with the non-magnetic layer; and a second ferromagnetic layer in contact with the pinned magnetic layer.
    Type: Grant
    Filed: April 9, 1999
    Date of Patent: October 9, 2001
    Assignee: NEC Corporation
    Inventor: Masafumi Nakada
  • Publication number: 20010017753
    Abstract: A magnetoresistive effect film achieves sufficiently large resistance variation ratio, sufficient switch connection force from an anti-ferromagnetic layer to a fixed magnetic layer, certainly maintains head resistance at a temperature higher than or equal to 200° C. with certainly maintaining good soft magnetic characteristics of NiFe layer or NiFe layer/CoFe layer, and is superior in thermal stability and has large magnetoresistance variation ratio (MR ratio). The magnetoresistive effect film is a stacked film which is consisted of a substrate, an buffer layer, a NiFe layer, a non-magnetic layer, a fixed magnetic layer, and an anti-ferromagnetic layer. A crystal grain size of the stacked film is greater than or equal to 8 nm and less than or equal to a total layer thickness of the stacked layer excluding the substrate and the buffer layer.
    Type: Application
    Filed: August 28, 1998
    Publication date: August 30, 2001
    Inventors: SHIGERU MORI, KAZUHIKO HAYASHI, MASAFUMI NAKADA
  • Patent number: 6215631
    Abstract: A magnetoresistive effect film has a lamination of an antiferromagnetic thin film, a magnetic thin film that is in contact with the antiferromagnetic thin film, a non-magnetic thin film that is in contact with the magnetic film, and another magnetic thin film that is in contact with the non-magnetic thin film. With a bias magnetic field of Hr on the antiferromagnetic thin film and a coercivity Hc2 of the other magnetic thin film, the condition Hc2<Hr is satisfied. The antiferromagnetic thin film is a laminate of a nickel oxide film and an iron oxide film having a thickness of 20 to 100 Å.
    Type: Grant
    Filed: October 9, 1997
    Date of Patent: April 10, 2001
    Assignee: NEC Corporation
    Inventors: Junichi Fujikata, Masafumi Nakada
  • Patent number: 6174736
    Abstract: There is provided a method of fabricating a ferromagnetic tunnel junction device, including the steps of (a) forming a first ferromagnetic layer on a substrate, (b) forming a tunnel barrier layer on the first ferromagnetic layer, (c) forming a second ferromagnetic layer on the tunnel barrier layer, (d) mechanically polishing end surfaces of the first ferromagnetic layer, the tunnel barrier layer, and the second ferromagnetic layer, and (e) etching the surfaces of the first ferromagnetic layer, the tunnel barrier layer, and the second ferromagnetic layer. The method provides a ferromagnetic tunnel junction device having a height defined with high accuracy, and including a tunnel barrier layer keeping first and second ferromagnetic layers in electrical isolation with each other.
    Type: Grant
    Filed: December 11, 1998
    Date of Patent: January 16, 2001
    Assignee: NEC Corporation
    Inventors: Yuji Tsukamoto, Hisanao Tsuge, Nobuyuki Ishiwata, Hisao Matsutera, Masafumi Nakada, Atsushi Kamijo
  • Patent number: 6147843
    Abstract: In a magnetoresistive element, an underlying metal layer is formed on a substrate, and a magnetoresistive layer is formed on the underlying metal layer. The underlying metal layer has a thickness of about 0.1 to 3.0 nm.
    Type: Grant
    Filed: January 24, 1997
    Date of Patent: November 14, 2000
    Assignee: NEC Corporation
    Inventors: Hidefumi Yamamoto, Kazuhiko Hayashi, Masafumi Nakada, Jun-Ichi Fujikata, Kunihiko Ishihara
  • Patent number: 6083632
    Abstract: A magnetoresistive effect film is formed by laminating a plurality of magnetic thin films onto a substrate with an intervening non-magnetic thin film, an antiferromagnetic thin film being provided so as to neighbor to one of the ferromagnetic thin film via this intervening non-magnetic thin film. With the bias magnetic field applied to the antiferromagnetic thin film being Hr and the coercivity of the other ferromagnetic thin film being Hc.sub.2, the condition Hc.sub.2 <Hr is satisfied. The antiferromagnetic thin film is made of either a cobalt oxide, a nickel oxide, or an a-phase ion oxide, or of an alloy of two or more of these materials, this being formed as a two-layer film.
    Type: Grant
    Filed: January 8, 1998
    Date of Patent: July 4, 2000
    Assignee: NEC Corporation
    Inventors: Junichi Fujikata, Masafumi Nakada
  • Patent number: 6051309
    Abstract: Disclosed are magnetoresistance effect films which have a magnetic thin film and an anti-ferromagnetically coupled magnetic multilayer thin film inserted into the interface between the non-magnetic thin film and the magnetic thin film, and a method for forming magnetoresistance effect films including the step of thermally treating the anti-ferromagnetic thin film and the magnetic multilayer thin film at a temperature of 200 to 300.degree. C. so as to generate one-directional anisotropy in the magnetic multilayer thin film, or the step of rotating by 90.degree. a magnetic field applied during the film formation so that the weak magnetization axes of the magnetic thin film and the magnetic multilayer thin film are orthogonal to each other.
    Type: Grant
    Filed: December 23, 1997
    Date of Patent: April 18, 2000
    Assignee: NEC Corporation
    Inventors: Jun-ichi Fujikata, Masafumi Nakada
  • Patent number: 6022633
    Abstract: A magnetoresistive effect element having a lamination structure of a free magnetic layer, a non-magnetic layer in contact with the free magnetic layer, a pinned magnetic layer in contact with the non-magnetic layer, and an anti-ferromagnetic layer in contact with the pinned magnetic layer, wherein the product of a saturation magnetization of the pinned magnetic layer and a thickness of the pinned magnetic layer is not higher than 2.times.10.sup.-9 T.multidot.m. The pinned magnetic layer may include a lanthanide metal.
    Type: Grant
    Filed: October 30, 1997
    Date of Patent: February 8, 2000
    Assignee: NEC Corporation
    Inventors: Kazuhiko Hayashi, Masafumi Nakada
  • Patent number: 5989690
    Abstract: Magnetic thin films 2 and 3 are stacked on a substrate 4 with a nonmagnetic thin film 1 interposed therebetween. An antiferromagnetic thin film 5 is arranged adjacent to one magnetic thin film 3. The inequality Hc.sub.2 <Hr is satisfied between a bias magnetic field Hr of the antiferromagnetic thin film 5 and coercive force Hc.sub.2 of the other magnetic thin film 2. At least a part of the antiferromagnetic thin film 5 comprises NiMn of an fct structure. Alternatively, the antiferromagnetic thin film 5 comprises a two-layer structure composed of a CoO layer deposited on a NiO layer to a thickness between 10 and 40 angstroms.
    Type: Grant
    Filed: March 20, 1998
    Date of Patent: November 23, 1999
    Assignee: NEC Corporation
    Inventors: Jun-Ichi Fujikata, Kazuhiko Hayashi, Hidefumi Yamamoto, Kunihiko Ishihara, Masafumi Nakada
  • Patent number: 5932343
    Abstract: A magnetoresistive effect element has an NiO layer, an intermediate layer, a first ferromagnetic layer, a first MR enhancement layer, a non-magnetic layer, a second MR enhancement layer, a second ferromagnetic layer, and a protective layer, laminated in sequence onto an underlayer, the intermediate layer being made of a mixture of nickel oxide and a ferrous oxide materials.
    Type: Grant
    Filed: August 12, 1997
    Date of Patent: August 3, 1999
    Assignee: NEC Corporation
    Inventors: Kazuhiko Hayashi, Masafumi Nakada
  • Patent number: 5917799
    Abstract: In a magneto-optical recording medium which includes a guide groove portion having a land area, a groove area, and a boundary area between the land area and the groove area, both of the land area and the groove area may have a V-shaped cross-section. At least one of the land area and the groove area may have a protruding portion which is formed in parallel to the guide groove portion and which has a width which is less than a half of a wavelength of a read laser beam.
    Type: Grant
    Filed: May 20, 1998
    Date of Patent: June 29, 1999
    Assignee: NEC Corporation
    Inventors: Masafumi Nakada, Masatsugu Ogawa
  • Patent number: 5889640
    Abstract: A magnetoresistive element generally includes consecutively an antiferromagnetic layer, a first ferromagnetic layer, a non-mangetic layer, and a second ferromagnetic layer. Instead of the non-magnetic layer, the magnetoresistive element may include a combination of a Co layer, a non-magnetic layer, and a Co layer. The antiferromagnetic layer is made of nickel oxide, a mixture of nickel oxide and cobalt oxide, or a laminate of nickel oxide and cobalt oxide. The ferromagnetic layer has a thickness of 1 to 10 nm, and the element has a height of 0.1 to 1 um. The non-magnetic layer has a thickness of 2 to 3 nm, and the antiferromagnetic layer has a thickness of 5 to 30 nm. The magnetoresistive element has an appropriate cross point, outputs an excellent reproduced signal, and has a desirable half-width with respect to the output signal.
    Type: Grant
    Filed: September 12, 1996
    Date of Patent: March 30, 1999
    Assignee: NEC Corporation
    Inventors: Kazuhiko Hayashi, Junichi Fujikata, Hidefumi Yamamoto, Kunihiko Ishihara, Masafumi Nakada