Structure and magnetic properties of Ni films obtained by pulsed laser ablation deposition

Pulsed laser ablation deposition was used to fabricate Ni films. The structure of the as-deposited films is hexagonal (a = 0.267 nm and c = 0.435 nm), and its resistivity is nearly one order of magnitude larger than the resistivity of bulk Ni. No spontaneous magnetization was observed in the as-deposited samples. Annealing above 200 degreesC induced an irreversible structural transformation from the metastable hexagonal phase to the stable face-centered-cubic (fee) one. Parallel to this transformation, the magnetic moment of the annealed Ni samples increased, and their resistivity decreased. On annealing at 440 degreesC, the structural transformation from the hexagonal-close-packed to the fee phase was completed, and the magnetic moment, Curie temperature, and electrical resistivity of the fee Ni films were found similar to the ones observed in bulk Ni. A direct correlation between the volume fraction of the fee Ni phase in our films and their magnetic moment was established.