Patents by Inventor Hoa Van Do
Hoa Van Do 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: 7180710Abstract: A magnetic recording medium has a laminated magnetic structure with at least three magnetic layers, wherein the magnetic layers have decreasing intrinsic coercivity H0 with distance from the write head. The write field at the center of each magnetic layer is greater than that layer's H0. The magnetic layers have different compositions and/or thicknesses and thereby different values of H0. The alloys used in the middle and upper magnetic layers are relatively “high-moment” alloys that would not ordinarily be used in magnetic recording media because they have relatively low S0NR, but the overall S0NR of the laminated magnetic structure is improved because of the effect of lamination. The middle and upper magnetic layers can be made substantially thinner, which enables the magnetic layers to be located closer to the write head, thereby exposing each of the magnetic layers to a higher write field.Type: GrantFiled: May 24, 2004Date of Patent: February 20, 2007Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Hoa Van Do, David Margulies, Hal J. Rosen, Natacha F. Supper
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Patent number: 7177118Abstract: A magnetic recording system uses a magnetic recording medium having a laminated magnetic structure with at least three magnetic layers, wherein the magnetic layers have decreasing intrinsic coercivity H0 with distance from the write head. The write field at the center of each magnetic layer is greater than that layer's H0. The magnetic layers have different compositions and/or thicknesses and thereby different values of H0. The alloys used in the middle and upper magnetic layers are relatively “high-moment” alloys that would not ordinarily be used in magnetic recording media because they have relatively low S0NR, but the overall S0NR of the laminated magnetic structure is improved because of the effect of lamination. The middle and upper magnetic layers can be made substantially thinner, which enables the magnetic layers to be located closer to the write head, thereby exposing each of the magnetic layers to a higher write field.Type: GrantFiled: May 24, 2004Date of Patent: February 13, 2007Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Hoa Van Do, David Margulies, Hal J. Rosen, Natacha F. Supper
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Patent number: 7125616Abstract: A magnetic recording disk has an antiferromagnetically-coupled (AFC) structure that has three lower ferromagnetic layers (LL1, LL2, LL3) and an upper ferromagnetic layer (UL), all four ferromagnetic layers being antiferromagnetically-coupled together across corresponding antiferromagnetically-coupling layers. The UL has a magnetization-remanence-thickness product (Mrt) greater than the Mrt each of the three lower layers LL1, LL2, LL3, and greater than the sum of the Mrt values of LL1 and LL3. The middle lower layer LL2 has an Mrt less than the Mrt of each of the other lower layers LL1 and LL3, and as a result the composite Mrt of the AFC structure is less than the composite Mrt of a conventional AFC structure having only a single lower layer. The AFC structure achieves this composite Mrt reduction without increasing the Mrt of any of the three lower layers above the maximum Mrt of the single lower layer in the conventional AFC structure.Type: GrantFiled: February 26, 2004Date of Patent: October 24, 2006Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Hoa Van Do, Eric Edward Fullerton, David Margulies, Andreas Moser
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Patent number: 7081309Abstract: A magnetic recording disk has an antiferromagnetically-coupled (AFC) structure that has an upper ferromagnetic layer (UL), and a lower ferromagnetic layer structure formed of two ferromagnetically-coupled lower layers (LL1, LL2). The UL is antiferromagnetically-coupled to the lower layer structure across an antiferromagnetically-coupling layer. LL1 and LL2 are ferromagnetically coupled across a ferromagnetic coupling layer so the magnetizations of LL1 and LL2 remain parallel in each remanent magnetic state, but are antiparallel to the magnetization of the UL in each remanent magnetic state. The UL has an Mrt greater than the sum of the Mrt values of LL1 and LL2.Type: GrantFiled: March 23, 2004Date of Patent: July 25, 2006Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Hoa Van Do, Eric Edward Fullerton, David Margulies, Andreas Moser
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Patent number: 6928723Abstract: An exchange-coupled magnetic structure of a cobalt-ferrite layer adjacent a magnetic metal layer is used in magnetorestive sensors, such as spin valves or tunnel junction valves. The exchange-coupled magnetic structure is used in a pinning structure pinning the magnetization of a ferromagnetic pinned layer, or in an AP pinned layer. A low coercivity ferrite may be used in an AP free layer. Cobalt-ferrite layers may be formed by co-sputtering of Co and Fe in an oxygen/argon gas mixture, or by sputtering of a CoFe2 composition target in an oxygen/argon gas mixture. Alternatively, the cobalt-ferrite layer may be formed by evaporation of Co and Fe from an alloy source or separate sources along with a flux of oxygen atoms from a RF oxygen atom beam source. Magnetoresistive sensors including cobalt-ferrite layers have small read gaps and produce large signals with high efficiency.Type: GrantFiled: December 23, 2003Date of Patent: August 16, 2005Assignee: International Business Machines CorporationInventors: Matthew Joseph Carey, Hoa Van Do, Robin Frederick Charles Farrow, Bruce Alvin Gurney, David Thomas Margulies, Ronald Franklin Marks, Philip Milton Rice, Ren Xu
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Patent number: 6835476Abstract: A magnetic recording medium for data storage uses a magnetic recording layer having at least two ferromagnetic films exchange coupled together antiferromagnetically across a nonferromagnetic spacer film. In this antiferromagnetically-coupled (AFC) recording layer the magnetic moments of the two ferromagnetic films are oriented antiparallel, and thus the net remanent magnetization-thickness product (Mrt) of the AFC recording layer is the difference in the Mrt values of the two ferromagnetic films. This reduction in Mrt is accomplished without a reduction in thermal stability of the recording medium. The lower ferromagnetic film in the AFC recording layer is a ferromagnetic CoCrFe alloy that does not require a nucleation layer between it and the Cr alloy underlayer. The medium with the CoCrFe alloy as the first or lower ferromagnetic film in the AFC recording layer has reduced intrinsic media noise.Type: GrantFiled: March 11, 2003Date of Patent: December 28, 2004Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Hoa Van Do, Mary F. Doerner, Eric Edward Fullerton, David T. Margulies, Natacha F. Supper
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Publication number: 20040180173Abstract: A magnetic recording medium for data storage uses a magnetic recording layer having at least two ferromagnetic films exchange coupled together antiferromagnetically across a nonferromagnetic spacer film. In this antiferromagnetically-coupled (AFC) recording layer the magnetic moments of the two ferromagnetic films are oriented antiparallel, and thus the net remanent magnetization-thickness product (Mrt) of the AFC recording layer is the difference in the Mrt values of the two ferromagnetic films. This reduction in Mrt is accomplished without a reduction in thermal stability of the recording medium. The lower ferromagnetic film in the AFC recording layer is a ferromagnetic CoCrFe alloy that does not require a nucleation layer between it and the Cr alloy underlayer. The medium with the CoCrFe alloy as the first or lower ferromagnetic film in the AFC recording layer has reduced intrinsic media noise.Type: ApplicationFiled: March 11, 2003Publication date: September 16, 2004Inventors: Hoa Van Do, Mary F. Doerner, Eric Edward Fullerton, David T. Margulies, Natacha F. Supper
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Publication number: 20040166371Abstract: A magnetic recording disk has a ferromagnetic recording layer and a “paramagnetic” write assist layer in contact and exchange coupled with the ferromagnetic recording layer. The write assist layer is a ferromagnetic material that has a Curie temperature less than the operating temperature of the disk drive so that at operating temperature and in the absence of a write field, the write assist layer is in its paramagnetic state and has no remanent magnetization. When a write field is applied in a direction opposite to the magnetization in previously written regions of the ferromagnetic recording layer, the write assist layer exhibits a magnetization aligned with the write field and assists the write field in reversing the magnetization in the ferromagnetic recording layer due to the exchange coupling.Type: ApplicationFiled: February 26, 2003Publication date: August 26, 2004Inventors: Andreas Klaus Dieter Berger, Hoa Van Do, Eric Edward Fullerton
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Patent number: 6773834Abstract: A laminated magnetic recording medium for data storage has an antiferromagnetically-coupled (AFC) layer and a single ferromagnetic layer spaced apart by a nonferromagnetic spacer layer. The AFC layer is formed as two ferromagnetic films antiferromagnetically coupled together across an antiferromagnetically coupling film that has a composition and thickness to induce antiferromagnetic coupling. In each of the two remanent magnetic states, the magnetic moments of the two antiferromagnetically-coupled films in the AFC layer are oriented antiparallel, and the magnetic moment of the single ferromagnetic layer and the greater-moment ferromagnetic film of the AFC layer are oriented parallel. The nonferromagnetic spacer layer between the AFC layer and the single ferromagnetic layer has a composition and thickness to prevent antiferromagnetic exchange coupling. The laminated medium has improved thermal stability and reduced intrinsic media noise.Type: GrantFiled: January 29, 2002Date of Patent: August 10, 2004Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Hoa Van Do, Eric Edward Fullerton, David Thomas Margulies, Hal Jervis Rosen
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Publication number: 20040134060Abstract: An exchange-coupled magnetic structure of a cobalt-ferrite layer adjacent a magnetic metal layer is used in magnetorestive sensors, such as spin valves or tunnel junction valves. The exchange-coupled magnetic structure is used in a pinning structure pinning the magnetization of a ferromagnetic pinned layer, or in an AP pinned layer. A low coercivity ferrite may be used in an AP free layer. Cobalt-ferrite layers may be formed by co-sputtering of Co and Fe in an oxygen/argon gas mixture, or by sputtering of a CoFe2 composition target in an oxygen/argon gas mixture. Alternatively, the cobalt-ferrite layer may be formed by evaporation of Co and Fe from an alloy source or separate sources along with a flux of oxygen atoms from a RF oxygen atom beam source. Magnetoresistive sensors including cobalt-ferrite layers have small read gaps and produce large signals with high efficiency.Type: ApplicationFiled: December 23, 2003Publication date: July 15, 2004Inventors: Matthew Joseph Carey, Hoa Van Do, Robin Frederick Charles Farrow, Bruce Alvin Gurney, David Thomas Margulies, Ronald Franklin Marks, Philip Milton Rice, Ren Xu
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Patent number: 6723450Abstract: A magnetic recording medium for data storage uses a magnetic recording layer having at least two ferromagnetic films with different remanent magnetization-thickness (Mrt) values that are coupled antiparallel across a nonferromagnetic spacer film predominantly by the dipole field (Hd) from the grains of the higher-Mrt ferromagnetic film. The material compositions and thicknesses of the ferromagnetic films and the nonferromagnetic spacer film are selected so that Hd predominates over any antiferromagnetic exchange coupling field (Haf) and is greater than the coercive field of the lower-Mrt ferromagnetic film. As a result, the magnetizations of the two ferromagnetic films are antiparallel in the two remanent magnetic states, and thus the net remanent magnetization-thickness product (Mrt) of the recording layer is the difference in the Mrt values of the two ferromagnetic films.Type: GrantFiled: March 19, 2002Date of Patent: April 20, 2004Assignee: Hitachi Global Storage Technologies Netherlands B.V.Inventors: Hoa Van Do, Mary F. Doerner, Eric Edward Fullerton, David Thomas Margulies, William G. McChesney, Manfred Ernst Schabes, Kai Tang
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Patent number: 6721144Abstract: An exchange-coupled magnetic structure of a cobalt-ferrite layer adjacent a magnetic metal layer is used in magnetorestive sensors, such as spin valves or tunnel junction valves. The exchange-coupled magnetic structure is used in a pinning structure pinning the magnetization of a ferromagnetic pinned layer, or in an AP pinned layer. A low coercivity ferrite may be used in an AP free layer. Cobalt-ferrite layers may be formed by co-sputtering of Co and Fe in an oxygen/argon gas mixture, or by sputtering of a CoFe2 composition target in an oxygen/argon gas mixture. Alternatively, the cobalt-ferrite layer may be formed by evaporation of Co and Fe from an alloy source or separate sources along with a flux of oxygen atoms from a RF oxygen atom beam source. Magnetoresistive sensors including cobalt-ferrite layers have small read gaps and produce large signals with high efficiency.Type: GrantFiled: January 4, 2001Date of Patent: April 13, 2004Assignee: International Business Machines CorporationInventors: Matthew Joseph Carey, Hoa Van Do, Robin Frederick Charles Farrow, Bruce Alvin Gurney, David Thomas Margulies, Ronald Franklin Marks, Philip Milton Rice, Ren Xu
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Publication number: 20030180577Abstract: A magnetic recording medium for data storage uses a magnetic recording layer having at least two ferromagnetic films with different remanent magnetization-thickness (Mrt) values that are coupled antiparallel across a nonferromagnetic spacer film predominantly by the dipole field (Hd) from the grains of the higher-Mrt ferromagnetic film. The material compositions and thicknesses of the ferromagnetic films and the nonferromagnetic spacer film are selected so that Hd predominates over any antiferromagnetic exchange coupling field (Haf) and is greater than the coercive field of the lower-Mrt ferromagnetic film. As a result, the magnetizations of the two ferromagnetic films are antiparallel in the two remanent magnetic states, and thus the net remanent magnetization-thickness product (Mrt) of the recording layer is the difference in the Mrt values of the two ferromagnetic films.Type: ApplicationFiled: March 19, 2002Publication date: September 25, 2003Inventors: Hoa Van Do, Mary F. Doerner, Eric Edward Fullerton, David Thomas Margulies, William G. McChesney, Manfred Ernst Schabes, Kai Tang
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Publication number: 20020098390Abstract: A laminated magnetic recording medium for data storage has an antiferromagnetically-coupled (AFC) layer and a single ferromagnetic layer spaced apart by a nonferromagnetic spacer layer. The AFC layer is formed as two ferromagnetic films antiferromagnetically coupled together across an antiferromagnetically coupling film that has a composition and thickness to induce antiferromagnetic coupling. In each of the two remanent magnetic states, the magnetic moments of the two antiferromagnetically-coupled films in the AFC layer are oriented antiparallel, and the magnetic moment of the single ferromagnetic layer and the greater-moment ferromagnetic film of the AFC layer are oriented parallel. The nonferromagnetic spacer layer between the AFC layer and the single ferromagnetic layer has a composition and thickness to prevent antiferromagnetic exchange coupling. The laminated medium has improved thermal stability and reduced intrinsic media noise.Type: ApplicationFiled: January 29, 2002Publication date: July 25, 2002Inventors: Hoa Van Do, Eric Edward Fullerton, David Thomas Margulies, Hal Jervis Rosen
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Publication number: 20020085321Abstract: An exchange-coupled magnetic structure of a cobalt-ferrite layer adjacent a magnetic metal layer is used in magnetorestive sensors, such as spin valves or tunnel junction valves. The exchange-coupled magnetic structure is used in a pinning structure pinning the magnetization of a ferromagnetic pinned layer, or in an AP pinned layer. A low coercivity ferrite may be used in an AP free layer. Cobalt-ferrite layers may be formed by co-sputtering of Co and Fe in an oxygen/argon gas mixture, or by sputtering of a CoFe2 composition target in an oxygen/argon gas mixture. Alternatively, the cobalt-ferrite layer may be formed by evaporation of Co and Fe from an alloy source or separate sources along with a flux of oxygen atoms from a RF oxygen atom beam source. Magnetoresistive sensors including cobalt-ferrite layers have small read gaps and produce large signals with high efficiency.Type: ApplicationFiled: January 4, 2001Publication date: July 4, 2002Inventors: Matthew Joseph Carey, Hoa Van Do, Robin Frederick Charles Farrow, Bruce Alvin Gurney, David Thomas Margulies, Ronald Franklin Marks, Philip Milton Rice, Ren Xu
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Patent number: 6372330Abstract: A laminated magnetic recording medium for data storage uses a magnetic recording layer having at least two antiferromagnetically-coupled (AFC) layers spaced apart by a nonferromagnetic spacer layer. Each AFC layer is formed as two ferromagnetic films antiferromagnetically coupled together across an antiferromagnetically coupling film that has a composition and thickness to induce antiferromagnetic coupling of the second film to the first film. The magnetic moments of the two antiferromagnetically-coupled films in each AFC layer are oriented antiparallel, and thus the net remanent magnetization-thickness product (Mrt) of each AFC layer is the difference in the Mrt values of the two ferromagnetic films. The nonferromagnetic spacer layer between neighboring AFC layers has a composition and thickness to prevent any antiferromagnetic coupling of the ferromagnetic films of one AFC layer with the ferromagnetic films of the neighboring AFC layer.Type: GrantFiled: July 26, 2000Date of Patent: April 16, 2002Assignee: International Business Machines CorporationInventors: Hoa Van Do, Eric Edward Fullerton, David Thomas Margulies, Hal Jervis Rosen
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Patent number: 5679431Abstract: A thin-film magnetic recording medium having a carbon overcoat composed of an overcoat sublayer and an overcoat surface layer is described. The overcoat surface layer is a hydrogen- or nitrogen-containing sputtered carbon layer with high wear-resistance. The overcoat sublayer functions to reduce the diffusion of nitrogen or hydrogen from the surface layer to the magnetic recording layer. Also described is a method of sputtering the nitrogen-containing surface layer in which the graphite target is attached to the target electrode by thermally conducting, electrically conducting materials.Type: GrantFiled: April 1, 1994Date of Patent: October 21, 1997Assignee: HMT Technology CorporationInventors: Ga-Lane Chen, Hoa Van Do