The electric field manipulation of magnetic anisotropy and domain configuration has been investigated in the artificial multiferroic Co/PMN-PT (011) heterostructure at room temperature. A uniaxial magnetic anisotropy is induced with the application of an electric field, which leads to an electrically switched anisotropic magnetoresistance with tunability as large as ∼29%. Furthermore, the magnetic domain structures of Co films are investigated by magnetic force microscopy under an in situ electric field, which exhibits direct evidence for electric field control of magnetism at the mesoscale. The converse magnetoelectric effect demonstrated in this multiferroic heterostructure has potential to be utilized in magnetoelectric devices with low power consumption.
The magnetism and photoluminescence (PL) of nickel-doped SnO2 nano-powders were studied in detail. A weak room temperature hysteresis is obtained in the pure SnO2 nano-powders, which means that no extra transition metal ions are needed for obtaining magnetism in SnO2 nano-powders. Furthermore, it is found that the measured magnetic moment per nickel ion is reduced with the doping content increasing. The ratio of ferromagnetic ordering moments to the measured magnetic moment is quickly decreased by nickel doping. This may be contributing to the anti-ferromagnetic interaction caused by nickel doping. The PL signal is split into two emission bands with annealing temperature increasing above 200 °C, which may be due to the reduction of twofold-coordinated tin oxygen-deficient centers. The ultraviolet emission band is separated into two peaks at higher doping content.
(100)-oriented MgO single crystals were irradiated to introduce point defects with different neutron doses ranging from 1.0×1016 to 1.0×1020 cm-2. The point defect configurations were studied with X-ray diffuse scattering and UV-Vis absorption spectra. The isointensity profiles of X-ray diffuse scattering caused by the cubic and double-force point defects in MgO were theoretically calculated based on the Huang scattering theory. The magnetic properties at different temperature were measured with superconducting quantum interference device (SQUID). The reciprocal space mappings (RSMs) of irradiated MgO revealed notable diffuse scattering. The UV-Vis spectra indicated the presence of O Frenkel defects in irradiated MgO. Neutron-irradiated MgO was diamagnetic at room temperature and became ferromagnetic at low temperature due to O Frenkel defects induced by neutron-irradiation.
N-implanted MgO single crystals were prepared and their magnetic properties were studied. High Resolution x-ray diffraction, photoluminescence, and x-ray photoelectron spectroscopy measurements confirmed that both intrinsic defects (Mg vacancies, oxygen vacancies) and extrinsic defects (N-related defects) were presented in the implanted samples. Ferromagnetism was detected in the samples. The saturation magnetization (Ms) of the samples increases with the concentrations of Mg vacancies and N-related defects. We conclude that the enhanced Ms should be ascribed to the synergistic effects of intrinsic and extrinsic defects. The magnetic properties of various composite defects were also studied by first principle calculations. The results suggest that the ferromagnetism is mainly originated from the configurations of VMg (Mg vacancy)+NO (N substituting for O).
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