Magnetic and morphological characteristics of nickel nanoparticles films produced by femtosecond laser ablation

We have used the technique of femtosecond (fs) laser ablation in a vacuum to produce films of nickel nanoparticles. A peculiarity of this fs laser deposition is the significant shape and orientation anisotropy of the nanoparticles, which are oblate ellipsoids with the major axis parallel to the deposition substrate. The deposited films present unique magnetic properties, and, in specific conditions, very high remanence ratios (up to 0.7) accompanied with relatively low values of saturation and coercive fields can be obtained. We have interpreted these results in terms of the mentioned anisotropies, and of the occurrence of a thermally induced in-plane tensile stress, which is a function of the nanoparticles size.