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Now showing items 61-80 of 106

  • Magnetism in thin films of CaB6 and SrB6 

    LUNNEY, JAMES GERARD; COEY, JOHN MICHAEL DAVID; LUNNEY, JAMES GERARD; VENKATESAN, MUNUSWAMY; COEY, JOHN MICHAEL DAVID (American Physical Society, 2004)
    Thin films of disordered hexaborides CaB6 and SrB6 deposited by pulsed-laser deposition on MgO (100) or Al2O3 (001) substrates are ferromagnetic. A typical room-temperature moment per unit area of substrate is 350 mB ...
  • Magnetite Schottky barriers on GaAs substrates 

    VAN DIJKEN, SEBASTIAN; COEY, JOHN MICHAEL DAVID (American Institute of Physics, 2005)
    Thin films of HfO2 produced by pulsed-laser deposition on sapphire, yttria-stabilized zirconia, or silicon substrates show ferromagnetic magnetization curves with little hysteresis and extrapolated Curie temperatures far ...
  • Magnetization and 57Fe hyperfine fields in Y2Fe17Z3-??(Z=H, C, or N) interstitial compounds 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1992)
    Measured magnetization and 57Fe hyperfine fields at T?_0 K for Y2Fe17 and Y2Fe17Z3-??, with Z=H, C, or N and ???_0.5, are analyzed to determine the influence of the interstitial atoms on the 3d magnetism. All are weak ...
  • Magnetization and Temperature Dependence of the Mossbauer Spectrum Shift for an Insulator. 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1969)
    The results of a Mossbauer-effect study of HoFeO3 in the temperature range 99-875?K are presented. Special attention is paid to the shift of the center of the spectrum and its temperature dependence both above and below ...
  • Magnetization of a Dy(Fe11Ti) single crystal 

    COEY, JOHN MICHAEL DAVID (American Physcial Society, 1990)
    Magnetization curves have been measured in the temperature range from 4.2 to 300 K along the [100], [110], and [001] directions of a Dy(Fe11Ti) single crystal in fields up to 7 T. The magnetic moment is along [100] below ...
  • Magnetocrystalline anisotropy of 3d-4f intermetallics: Breakdown of the linear theory. 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1994)
    Applicability of linear theory to magnetic anisotropy of 3d-4f intermetallics is investigated with particular reference to Sm2Fe17N3. A general quantitative criterion for the breakdown of the linear theory is established, ...
  • Magnetoresistance and electrical hysteresis in stable half-metallic (La0.7Sr0.3 MnO3 and Fe3O4 nanoconstrictions 

    COEY, JOHN MICHAEL DAVID (American Institute of Physics, 2005)
    We have studied the transport properties of mechanically stable Fe3O4 and La0.7Sr0.3MnO3 nanoconstrictions patterned by focused ion-beam milling. The magnetoresistance decreases with the square of the applied voltage and ...
  • Magnetoresistance in magnetic tunnel junctions with amorphous electrodes 

    FENG, GEN; COEY, JOHN MICHAEL DAVID (IEEE, 2005)
    Magnetic tunnel junctions (MTJs) with amorphous CoFeB and Co2MnSi electrodes were fabricated and examined. In the case of [Co90Fe10]100 B , the = 32%boron addition reduces the magnetization by 30% compared to Co90Fe10, ...
  • Magnetoresistance in nanostructured Co-Ag prepared by mechanical alloying 

    COEY, JOHN MICHAEL DAVID (IEEE, 1993)
    Fine cobalt and silver powders have been ball-milled to yield a granular solid of composition Co30Ag70 in the form of coarse powder. The material is an intimate mixture of grains of fcc Co in a silver matrix. The cobalt ...
  • Magnetoresistance in nanostructured Co-Ag prepared by mechanical-alloying 

    FAGAN, ANDREW JOHN; COEY, JOHN MICHAEL DAVID (IEEE, 1994)
    Fine cobalt and silver powders have been ball-milled to yield a granular solid of composition CoSoAg7a in the form of coarse powder. The material is an intimate mixture of grains of fcc CO in a silver matrix. The cobalt ...
  • Magnetoresistance of chromium dioxide powder compacts 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1998)
    Cold-pressed powders of the half-metallic ferromagnet CrO2 are dielectric granular metals. Hysteretic magnetoresistance with maxima at the coercive field arises from interparticle contacts. Dilution with insulating ...
  • Magnetoresistance of half-metallic oxide nanocontacts 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 2001)
    The conductivity of a nanocontact between two crystallites of magnetite (Fe3O4) was studied. It was found that the conductivity can increase sixfold at room temperature in an applied field of 7 mT (70 Oe). This large ...
  • Magnetoresistance of magnetite point contacts and nanoconstrictions 

    COEY, JOHN MICHAEL DAVID (American Institute of Physics, 2005)
    Point contacts of magnetite exhibit large, reversible increases of conductance by a factor of up to 5 in the presence of a small magnetic field (<10?mT), provided the conductance is less than the quantum of conductance G0 ...
  • MgO-based double barrier magnetic tunnel junctions with thin free layers 

    FENG, GEN; VAN, DIJKEN SEBASTIAN; COEY, JOHN MICHAEL DAVID (American Institute of Physics, 2009)
    The free layer thickness (tfree) in double barrier magnetic tunnel junctions (DMTJs) based on crystalline MgO barriers and CoFeB ferromagnetic layers has been varied from 0.5 to 3.0 nm in order to investigate its effect ...
  • Mossbauer spectra of mixed crystals: diamagnetically - substituted yttrium iron garnet in the critical region 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1972)
    There is a range of temperature where the Mossbauer spectra of 57Fe3+ in diamagnetically substituted magnetically ordered iron oxides show broad lines and may be reproduced by local-molecular-field theory. The lines can ...
  • Negative magnetoresistance in dual spin valve structures with a synthetic antiferromagnetic free layer 

    FOWLEY, CIARAN; COEY, JOHN MICHAEL DAVID (IEEE, 2009)
    Giant magnetoresistance (GMR) in spin valves is due to spin-dependent scattering occurring at ferromagnet/normal metal (F/N) interfaces and/or in the ferromagnetic layers. In a spin valve with a typical F/N/F structure ...
  • Negative magnetoresistance in Fe3O4/Au/Fe spin valves 

    VAN, DIJKEN SEBASTIAN; COEY, JOHN MICHAEL DAVID (American Physical Society, 2004)
    The structural, electrical, and magnetic properties of Fe3O4 /Au/Fe spin valves on MgOs001d are presented. In contrast to more conventional spin valve structures, the current-in-plane resistance of the Fe3O4 /Au/Fe ...
  • Nickel sulfide - an itinerant electron antiferromagnet. 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1974)
    Antiferromagnetic nickel sulphide has a small temperature-independent magnetic susceptibility. The ordered moment per nickel atom, measured with neutrons, decreases from 1.45?B to 1.00?B at 4.2 K with a decrease of 0.6% ...
  • Noise in MgO barrier magnetic tunnel junctions with CoFeB electrodes; influence of annealing temperature 

    FENG, GEN; COEY, JOHN MICHAEL DAVID (American Institute of Physics, 2007)
    Low frequency noise has been measured in magnetic tunnel junctions with MgO barriers and magnetoresistance values up to 235%. The authors investigated the noise for different degrees of crystallization and CoFeB/MgO ...