Magnetic properties of Ni nanowires in self-assembled arrays

Magnetic properties of Ni nanowires electrodeposited into self-assembled po rous alumina arrays have been investigated. By anodizing aluminum in sulfur ic acid and immersing the as-anodized template into phosphoric acid for dif ferent lengths of time, we are able to vary the diameters of the subsequent ly deposited nanowires between 8 and 25 nm. The coercivity measured along w ire axis first increases with the wire diameter, reaches a maximum of 950 O e near a diameter of 18 nm, and then decreases with further increase of wir e diameter. The dependence of the magnetization of Ni nanowires is found to follow Bloch's law at low temperature but with the Bloch exponent decreasi ng from the hulk value and the Bloch constant increasing from the bulk valu e by an order of magnitude.