Magnetic Behaviour of Ni Nanoparticles Films Produced by Two Laser Irradiations in Vacuum

Magnetic nanoparticles-assembled films are good candidates to obtain peculiar macroscopic magnetic properties which can be optimized for specific technological applications in a wide range of magnetomechanical and magnetoelectrical devices, by controlling the morphology and topology of the constituent nanoparticles (NPs). In fact, the physical properties of the systems of NPs associated to their small size and large surface-to-volume ratio can lead to peculiar properties that cannot be found in corresponding bulk materials. Despite the huge research efforts in the field of physical and chemical methods for the preparation of magnetic nanostructured systems - with reproducible narrow size distribution, controllable shape and proper NPs topology to tune suitable interplay between exchange and dipolar magnetic interactions - there is still a great need of simply, cost-effective synthesis techniques able to assure contemporaneously all the above mentioned characteristics. Femtosecond pulsed laser deposition (fs-PLD) in vacuum has been demonstrated to be a powerful and versatile tool for the production of metal and semiconductor nanoparticle-assembled films. In this work we study the possibility to modify the size and size distribution of the NPs produced by fs-PLD, by using the irradiation of the NPs plume with a secondary UV laser beam, and the consequent changes in the macroscopic magnetic behavior of the NP systems.