Browsing by Author "COEY, JOHN MICHAEL DAVID"
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Annealing of CoFeB/MgO based single and double barrier magnetic tunnel junctions: Tunnel magnetoresistance, bias dependence, and output voltage
FENG, GEN; FENG, JIA-FENG; VAN, DIJKEN SEBASTIAN; COEY, JOHN MICHAEL DAVID (American Institute of Physics, 2009)Co40Fe40B20/MgO single and double barrier magnetic tunnel junctions (MTJs) were grown using target-facing-target sputtering for MgO barriers and conventional dc magnetron sputtering for Co40Fe40B20 ferromagnetic electrodes. ... -
Atomic coordination and the distribution of electric field gradients in amorphous solids
COEY, JOHN MICHAEL DAVID (American Physical Society, 1981)The observation of nuclear quadrupole interactions in amorphous solids provides a unique possibility of obtaining information about the angular distribution of local ionic coordinations, complementary to the information ... -
Bias voltage dependence of inverted magnetoresistance on the annealing temperature in MgO-based magnetic tunnel junctions
FENG, GEN; FENG, JIA-FENG; COEY, JOHN MICHAEL DAVID (Elsevier, 2009)MgO-based magnetic tunnel junctions (MTJs) with a layer sequence Ir22Mn78 or Fe50Mn50 (10 nm)/CoFe (2 nm)/Ru (0.85 nm)/CoFeB (0.5t<2 nm)/MgO (2.5 nm)/CoFeB (3 nm) have been fabricated. The bias voltage dependence of tunneling ... -
Charge dynamics in the half-metallic ferromagnet CrO2
COEY, JOHN MICHAEL DAVID (American Physical Society, 1999)Infrared spectroscopy is used to investigate the electronic structure and charge carrier relaxation in crystalline films of CrO2 which is the simplest of all half-metallic ferromagnets. Chromium dioxide is a bad metal at ... -
Chirality of electrodeposits grown in a magnetic field
COEY, JOHN MICHAEL DAVID (American Physical Society, 2004)Electrodeposits grown around a point cathode in a flat, horizontal electrochemical cell have fractal form. When grown in the presence of a perpendicular applied magnetic field, the deposits develop a spiral structure with ... -
Coercivity mechanism of melt-spun Sm(Fe11Ti)
COEY, JOHN MICHAEL DAVID (IEEE, 1990)Hysteresis loops of randomly oriented grains with uniaxial anisotropy were computed on the basis of an array of 27 Wigner-Seitz cells representing crystallites which interact by exchange coupling at the grain boundaries. ... -
Comment on the giant quadrupole interaction in EuxRhB.
COEY, JOHN MICHAEL DAVID (American Physical Society, 1986) -
Comparison between the amorphous and crystalline (A15) phases of Nb3Ge
COEY, JOHN MICHAEL DAVID (American Physical Society, 1978)A comparative study on the superconducting and the normal-state properties of the amorphous, low-Tc (3.9 K) and the crystalline, high-Tc (2.18 K) phases of Nb3Ge suggests that changes in the strength of electron-phonon ... -
Controlled fabrication of nickel perpendicular nanocontacts using focused ion beam milling
COEY, JOHN MICHAEL DAVID (American Institute of Physics, 2006)A method for the controlled fabrication of a nickel perpendicular nanocontact with diameters less than 5 nm is reported. The method involves milling pores through the 100 nm thick silicon nitride membrane using a focused ... -
Correlation between perpendicular exchange bias and magnetic anisotropy in IrMn/[Co/Pt](n) and [Pt/Co](n)/IrMn multilayers
VAN DIJKEN, SEBASTIAN; COEY, JOHN MICHAEL DAVID (American Institute of Physics, 2005)Perpendicular exchange bias has been observed for IrMn/[Co/Pt]n and [Pt/Co]n/IrMn multilayers in the as-deposited state. The exchange bias field is largest when the IrMn film is grown on magnetically saturated Co/Pt ... -
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) -
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 ...