Elastomagnetic and Elastoresistive Effects in CoFe Films Produced by Femtosecond Pulsed Laser Deposition

Femtosecond pulsed laser deposition, carried out in high vacuum, leads the ablation of any target material, producing a plume of nano-drops which are deposited on a substrate as particles, preserving the parent material composition. The deposited nanoparticles (NPs) exhibit a characteristic disk-shape with a major diameter ranging from 5 nm up to 60 nm and a thickness ranging from 1 nm up to 10 nm. Also when the particles form a thick layer, they remain separated by an interface of free volume. This characteristic morphology of the deposited films gives an interplay of interparticle and intraparticle physical correlations which deeply differentiates their properties from those of similar nanogranular films deposited by other techniques. This investigation is focused on the influence of the novel structural conditions on the coupling between strain and magnetization, and/or strain and resistivity, in Co₅₀Fe₅₀ NP films deposited on Kapton substrate. Due to the NP nature of the films, these couplings are substantially different from standard magnetostrictive and piezoresistive effects. Magnetization and resistivity versus applied strain were studied, thus evidencing novel elastoresistive and elastomagnetic functionalities and evaluating their relative sensitivities. The limits and potentiality for the application of the new NP magnetic films in microelectromechanical systems (MEMS) will be briefly discussed.