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Now showing items 69-88 of 103

  • 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 ...
  • Non-equilibrium gas-phase nitrogenation 

    COEY, JOHN MICHAEL DAVID (IEEE, 1994)
    Non-equilibrium nitrogenation of transition-metal rich rare-earth intermetallics can be used to increase the nitrogen content beyond its equilibrium concentration. For example, nitrogenation of Sm2Fel7 using ammonia ...
  • Noncollinear spin arrangement in ultrafine ferrimagnetic crystallites 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1971)
    Mossbauer-effect measurements on extremely small (~60 ?) crystallites of ?-Fe2O3 show that the spin configuration differs from the Neel type found in large crystallites. It is proposed that the ions in the surface layer ...
  • Nucleation field and energy product of aligned two-phase magnets - progress towards the '1 MJ/m3' magnet 

    COEY, JOHN MICHAEL DAVID (IEEE, 1993)
    Exchange hardening of nanostructured two-phase systems composed of an aligned hard phase and a soft phase with high magnetization is investigated using a micromagnetic approach which accounts for intereactions between the ...
  • Observation of intermultiplet transitions in Sm(Fe11Ti) by inelastic neutron scattering 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1990)
    Magnetic neutron spectroscopy of SMFe11Ti reveals a dispersionless electronic excitation corresponding to transitions between levels of the exchange-split ground- and first-excited-state multiplets of the Sm3+ ion. The ...
  • Permanent magnet variable flux sources. 

    COEY, JOHN MICHAEL DAVID (IEEE, 1994)
    Rotatable transversely-magnetized permanent magnet rods can be used to generate variable, uniform magnetic fields or field gradients. A four-rod device for use at the specimen stage of an optical microscope is described ...
  • Perpendicular magnetic-anisotropy in iron films produced by laser chemical vapor-deposition of FE(CO)5 

    LUNNEY, JAMES GERARD; COEY, JOHN MICHAEL DAVID (IEEE, 1990)
    Uniform thin films of polyc r y s t a l l i n e a -iron are obtained by decomposing a stream of Fe(C0)s in a flow reactor using 193 nm ArF excimer laser pulses. The films are optically flat and 2.6 pm thick, but have ...
  • Point contact Andreev reflection by nanoindentation of polymethyl methacrylate 

    COEY, JOHN MICHAEL DAVID (American Institute of Physics, 2006)
    A versatile technique for performing spin polarization measurements via point contact Andreev reflection has been developed. This technique involves depositing a superconductor lead onto a thin film of the material to ...
  • Quantised conductance in a contact between metallic oxide crystals 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1998)
    The conductance of a point contact between two crystals of metallic (La0.75Sr0.25)MnO3 shows steps as the contact is broken. A histogram of the conductance values observed in 60 breaks exhibits a series of sharp peaks at ...
  • Quantized conductance in a contact between metallic oxide crystals 

    LUNNEY, JAMES GERARD; COEY, JOHN MICHAEL DAVID (American Physical Society, 1998)
    The conductance of a point contact between two crystals of metallic (La0.75Sr0.25)MnO3 shows steps as the contact is broken. A histogram of the conductance values observed in 60 breaks exhibits a series of sharp peaks at ...
  • Raman spectroscopy of ferromagnetic CrO2 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1999)
    Polarized Raman spectra of the ferromagnetic metal CrO2 were measured in a broad temperature range including Tc'390 K. The Raman-allowed modes of A1g , B1g , B2g , and Eg symmetry were identified and compared to the ...