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Theodoropoulou N Hebard AF Overberg ME Abernathy CR Pearton SJ Chu SN Wilson RG 《Physical review letters》2002,89(10):107203
Ion implantation of Mn ions into hole-doped GaP has been used to induce ferromagnetic behavior above room temperature for optimized Mn concentrations near 3 at. %. The magnetism is suppressed when the Mn dose is increased or decreased away from the 3 at. % value, or when n-type GaP substrates are used. At low temperatures the saturated moment is on the order of 1 Bohr magneton, and the spin wave stiffness inferred from the Bloch-law T(3/2) dependence of the magnetization provides an estimate T(c)=385 K of the Curie temperature that exceeds the experimental value, T(c)=270 K. The presence of ferromagnetic clusters and hysteresis to temperatures of at least 330 K is attributed to disorder and proximity to a metal-insulating transition. 相似文献
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B.-S. Jeong S.J. Pearton Y.W. Heo D.P. Norton A.F. Hebard 《Journal of magnetism and magnetic materials》2008
Hall effect measurements were performed on epitaxial CoxTi1−xO2–δ thin films grown on (0 0 1) LaAlO3 by reactive RF magnetron co-sputter deposition. Magnetization measurements reveal ferromagnetic behavior in M–H loop at room temperature for CoxTi1−xO2–δ thin films for which x?0.02. An anomalous Hall effect was observed for Co0.10Ti0.90O2−δ films grown with the partial pressure of water P(H2O)=4×10−4 Torr or less. These films exhibit a positive ordinary Hall coefficient and a positive magnetoresistance. X-ray diffraction on films grown under these conditions shows evidence for TinO2n−1 phase due to the deficiency of oxygen. In contrast, Hall measurements taken for undoped and Co-doped TiO2 thin films grown under more oxidizing conditions show only the ordinary Hall effect with a negative Hall coefficient consistent with n-type conduction. For these films, the magnetoresistance was positive and increased monotonically with increasing magnetic field. The results suggest that Co-doped TinO2n−1 may be a dilute magnetic semiconducting oxide for which the carriers couple to the spin polarization. 相似文献
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