Fabrication and temperature dependent magnetic properties of nickel nanowires embedded in alumina templates

Nickel nanowires (NWs) of 98 nm diameter and 17 micron length were fabricated by electrodeposition in anodic aluminum oxide (AAO) membranes. Structural analyses reveal that the NWs have face centered cubic (fcc) structure with preferred orientation along (111) plane. Low temperature magnetic measurements (10–300 K) show that coercivity (Hc) of nanowires increases with decreasing temperature following Kneller׳s law similar to the ferromagnetic nanoparticle system. In addition, the saturation magnetization follows the modified Bloch׳s law in the temperature range 50–300 K. However, at temperatures below 50 K there is an abrupt increase in net magnetization of the NWs that has been attributed to the presence of paramagnetic impurities in the samples that are activated at low temperatures and at high fields.