科研之友
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摘要
Co nanowire arrays have been fabricated into anodic aluminum oxide templates at 20 degrees C by dc electrodeposition. It is shown that Co nanowires fabricated at lower and higher growth voltages have a hexagonal close packing (hcp) structure with preferred [100] orientation along the nanowire axis and a face-centered cubic (fcc) structure with preferred [220] orientation, respectively. With increasing growth voltage, the room-temperature coercivity along the nanowire axis is enhanced gradually. For fcc Co nanowires, the coercivity increases monotonically with increasing temperature while for hcp Co nanowires, a minimal coercivity is obtained along both parallel-to-axis and perpendicular-to-axis orientations with the temperature rising from 50K to 390 K. The abnormal temperature dependence of the coercivity can be attributed to the competition between the shape anisotropy and magnetocrystalline anisotropy as a function of temperature.
