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Now showing items 21-40 of 158

  • Critical behavior of La0.75Sr0.25MnO3 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 2002)
    Magnetization, susceptibility, and specific heat measurements were made on a single crystal of La0.75Sr0.25MnO3. The ferromagnetic-to-paramagnetic phase transition was found at 346 K and four critical exponents were measured ...
  • Crystal Fields in Nd2Fe14B 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1984)
    The leading terms in the crystal field at both rare-earth sites in the new permanent magnet alloy Nd2Fe14B are B20 and B22s. The sign of B20 explains the variation of the anisotropy constant K1 reported by Sagawa et al. ...
  • Current trends in amorphous magnetism 

    COEY, JOHN MICHAEL DAVID (IEEE, 1984)
    Recent research on some topics in amorphous magnetism is reviewed and questions are posed which should be answered by future work. The topics are i) appearance of magnetism in binary alloys of the 3d transition elements ...
  • Cylindrical permanent-magnet structures using images in an iron shield 

    COEY, JOHN MICHAEL DAVID (IEEE, 2003)
    We report on cylindrical permanent-magnet structures that exploit the image effect in a surrounding circular soft-iron sheath. We present the theory for a general multipole ring, where the polarization direction ? = (n + ...
  • Cylindrical permanent-magnet structures using images in an iron shield 

    Peng, Quanling; MCMURRY, SARA; COEY, JOHN MICHAEL DAVID (IEEE, 2003)
  • Dependence of charge carrier injection on the interface energy barrier in short-channel polymeric field effect transistors 

    COEY, JOHN MICHAEL DAVID; STAMENOV, PLAMEN (2012)
    The influence of contact materials on the electrical characteristics of field-effect transistors made from poly(3-hexylthiophene) with short-channel lengths of 80nm is investigated. The thermally activated output current ...
  • Domain-wall dynamics in aligned bound Sm2Fe17 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1996)
    ac susceptibility (?ac=??-j??) of an aligned bound Sm2Fe17 powder sample has been measured along the easy direction as a function of temperature, frequency, warming rate, and time. Anomalous behavior has been found in that ...
  • Dynamic response of ammonia sensors constructed from polyaniline nano?bre ?lms with varying morphology 

    COEY, JOHN MICHAEL DAVID; STAMENOV, PLAMEN (Elsevier, 2012)
    Polyaniline is acid-doped with HCl, HNO3, HClO4, HBr or H2SO4 to yield thin films that are nanofibrous or dense. The nanofibrous films show a faster response to ammonia gas, and the response is greater when the films are ...
  • The effect of magnetic annealing on barrier asymmetry in Co40Fe40B20/MgO magnetic tunnel junctions 

    COEY, JOHN MICHAEL DAVID; FENG, JIA-FENG (2010)
    We demonstrate that high-quality magnetic tunnel junctions with Co40Fe40B20 electrodes and crystalline MgO barriers, which show a 230% tunneling magnetoresistance ratio at room temperature, can be successfully fabricated ...
  • Effects of Fe, Cu, Zr, and Ti on the magnetic properties of SmCo-1:7 magnets 

    VENKATESAN, MUNUSWAMY; COEY, JOHN MICHAEL DAVID (IEEE, 2002)
    The effect of Fe, Cu, Zr, and Ti substitution on magnetic properties of SmCo 1 : 7 magnets at temperatures up to 500 C were studied. As-milled amorphous Sm(Co,Fe,Cu,Ti???Zr)7 magnets crystallized in the TbCu7-type ...
  • Electrodeposited FePt films 

    COEY, JOHN MICHAEL DAVID (IEEE, 2003)
    A novel bath for electrodepositing FePt films was developed and films were electrodeposited on copper substrates with thickness up to 0.45 m. The magnetic and structural properties of the films were measured. The films ...
  • Electrodeposition of coercive L10 FePd and FePt magnets 

    COEY, JOHN MICHAEL DAVID (Elsevier, 2010)
    We report the preparation, characterization of structure and magnetic properties of electrodeposited L10 FePt films with high coercivity. Equiatomic as-deposited films are nanocrystalline, soft and magnetically isotropic. ...
  • Electron and spin transport studies of gated lateral organic devices 

    COEY, JOHN MICHAEL DAVID; STAMENOV, PLAMEN (2012)
    In view of the many, often contradictory, reports of magneto-resistance (M R) in spin valve stacks containing a layer of organic semiconductor, mostly of the small molecule variety, we have investigated interdigitated ...
  • Electron localization in mixed-valence manganites 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1995)
    Mixed-valence manganites (A3+0.7B2+0.3)MnO3 exhibit a resistivity peak with giant negative magnetoresistance below the Curie point. Residual resistivity ranges from 5?10-8 to 8?103 m, but the electronic heat capacity when ...
  • Electronic properties of Sr14Cu24O41 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1989)
    Crystals of orthorhombic Sr14Cu24O41 are semiconducting, with an activation energy of 0.18(2) eV for conduction along c, the direction lying parallel to both the (Cu2O3) planes and the (CuO2) chains. The magnetic susceptibility ...
  • Evidence for selective imaging of different magnetic ions on the atomic scale by using a scanning tunnelling microscope with a ferromagnetic probe tip. 

    SHVETS, IGOR; COEY, JOHN MICHAEL DAVID (IOP Publishing, 1992)
    Atomic resolution has been obtained on a magnetite (Fe3O4(001)) surface using a scanning tunnelling microscope with nonmagnetic tungsten and ferromagnetic iron tips. Selective imaging of Fe2 + and Fe3 + on B-sites is ...
  • Evidence for two-band magnetotransport in half-metallic chromium dioxide 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 2000)
    Magnetotransport measurements were made on patterned, (110) oriented CrO2 thin films grown by the high-pressure, thermal decomposition of CrO3 onto rutile substrates. The low-temperature Hall effect exhibits a sign reversal ...
  • Exchange coupling and energy product in random two-phase aligned magnets. 

    COEY, JOHN MICHAEL DAVID (IEEE, 1994)
    Size effects in two-phase Boolean magnets composed of an aligned hard phase and a soft phase with high magnetization are investigated. In 'overcritical' magnets, where the size of the soft regions is larger than the Blochwall ...
  • Exchange coupling and the grain boundary in magnetic nanocomposites 

    COEY, JOHN MICHAEL DAVID (IEEE, 1997)
    The grain boundary phase/material found to be present in two-phase mechanically alloyed nanocomposites of Sm2Fel7N3/Fe and NdzFe14B/Fe was characterized using Mossbauer spectroscopy and magnetization measurements. The ...
  • Exchange-biased magnetic tunnel junctions with antiferromagnetic epsilon-Mn3Ga 

    COEY, JOHN MICHAEL DAVID; VENKATESAN, MUNUSWAMY; STAMENOV, PLAMEN (2012)
    Oriented c-axis films of the hexagonal triangular antiferromagnetic ?-Mn3Ga have been used in bottom-pinned synthetic antiferromagnetmagnetic tunnel junctions with MgO barriers, which show up to 150% tunneling magnetoresistance ...