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Now showing items 21-40 of 107

  • 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 ...
  • 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 ...
  • 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 ...
  • Fabrication of magnetic force microscopy tips by electrodeposition and focused ion beam milling 

    COEY, JOHN MICHAEL DAVID (IEEE, 2008)
    A method is described for the fabrication of magnetic force microscopy tips via localized electrodeposition and focused ion beam milling departing from commercial tapping mode tips. Very high aspect ratios and interacting ...
  • Ferromagnetic nanoparticles with strong surface anisotropy: Spin structures and magnetisation processes 

    COEY, JOHN MICHAEL DAVID (American Physcial Society, 2008)
    Monte Carlo simulations are used to investigate the effect of surface anisotropy on the spin configurations and hysteresis loops of ferromagnetic nanoparticles. Spherical particles of radius ?a are composed of N atoms ...
  • Ferromagnetism in Fe-doped SnO2 thin films 

    VENKATESAN, MUNUSWAMY; COEY, JOHN MICHAEL DAVID (American Physical Society, 2004)
    Thin films grown by pulsed-laser deposition from targets of Sn0.95Fe0.05O2 are transparent ferromagnets with Curie temperature and spontaneous magnetization of 610 K and 2.2?A?m2?kg?1, respectively. The 57Fe Mossbauer ...
  • Field induced transition in the paramagnetic state of (Sm0.65Sr0.35))MnO3 associated with matnegic clusters 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1999)
    The susceptibility of (Sm0.65Sr0.35)MnO3 shows an unusual temperature dependence above the Curie temperature which is attributed to the presence of small manganese-ion clusters with S?9. A field-induced transition is ...
  • Gas-phase interstitial modification of rare-earth intermetallics. 

    COEY, JOHN MICHAEL DAVID (IEEE, 1992)
    The gas-phase interstitial modification of rare-earth intermetallics is studied. Net reaction energies for nitrogen in Sm2Fe17 and Nd(Fe11Tl) are U 0=-57 kJ/mole and U0=-51 kJ/mole, respectively. The equilibrium nitrogen ...
  • Giant energy product in nanostructured two-phase magnets 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1993)
    Exchange hardening of nanostructured two-phase systems composed of an aligned hard phase and a soft phase with high magnetization is investigated using an approach which yields analytic nucleation fields from the micromagnetic ...
  • Giant magnetoresistive effects in a single element magnetic thin film. 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1996)
    By exploiting the simplicity of a novel transport measurement on a ferromagnetic striped domain structure in a thin film of cobalt, we report the first direct observation of ferromagnetic domain wall scattering and what ...
  • Giant transverse hysteresis is an asperomagnet 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1990)
    Comparison of the magnetoresistance of amorphous thin films of Tb80U20 and the nonmagnetic analog Y80U20 reveals hysteresis for the terbium alloy, which extends to fields in excess of 8 T at 4.2 K. Hysteresis is found in ...
  • Heat capacity and metal-insulator transition in Ti4O7 single crystals' 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1974)
    Heat-capacity and entropy changes at the metal-insulator transitions have been measured on Ti4O7 single crystals. The 130-K transition is related to a disordering of the Ti3+ and Ti4+ chains at the unit cell level. Ti3+ ...
  • Heat capacity of nichel sulfide and its semimetal-metal transition 

    COEY, JOHN MICHAEL DAVID (American Physical Society, 1974)
    Heat-capacity measurements have been made from 5 to 330 K on NiS which shows a nonmetal-metal transition at 265 K, and on Ni0.95S which is metallic at all temperatures. The low-temperature data yield electronic specific-heat ...