Diameter and Temperature Dependent Structure and Magnetic Properties of Electrodeposited CoNiCu Alloy Nanowires
摘要
CoNiCu alloy nanowires were fabricated by electrodeposition into the pores of anodised aluminium oxide (AAO) templates. Here, we have investigated four samples of CoNiCu nanowires with different alumina oxide template pore diameters 40 nm, 100 nm, 160 nm and 200 nm. Transmission electron microscopy and scanning electron microscopy images confirms that the wires are uniform, continuous, and densely packed wires. The presence of (111) (200) and (220) XRD reflections observed at 2θ ~ 44.9°, 52° and 76°, indicate that these nanowires have purely face-centred cubic structure. A significant increase in coercivity is observed as the diameter and temperature changes. The coercivity of CoNiCu nanowires are found 2000 Oe for 40 nm and 488 Oe for 200 nm diameter when the applied field is parallel to the wire axis. The coercivity is 363 Oe for 40 nm and 192 Oe for 200 nm diameter when the applied field is perpendicular to the wire axis. A high value of coercivity parallel to the wire axis attributed to dipolar interactions and substantial shape anisotropy. A temperature dependence of the coercivity has also been observed for all the diameter. For 40 nm nanowires the value of coercivity is 2000 Oe at 300 K and 2892 Oe at 50 K, while for 200 nm it is 488 Oe at 300 K and 863 Oe at 50 K when the field is applied parallel to the wire axis. The increase in coercivity at low temperature is due to the freezing of thermal fluctuations blocks where each domain in a fixed magnetisation state.