Ferromagnetic shape memory thin films and nanodisks: tuning properties by thickness, lattice mismatch and lateral confinement

Ferromagnetic martensitic NiMnGa Heusler alloys are promising materials potentially exploitable for the fabrication of microdevices based on novel actuation mechanisms [1]. In bulk materials, giant strains obtainable by magnetomechanical effects based on the twin variant reorientation induced by a magnetic field (MIR), are higher than typical magnetostriction and state-of-the-art piezoelectric values [2]. Moreover, the coupling between magnetic and structural degrees of freedom leads to several multifunctional properties (e.g. "giant" magnetomechanical, magnetocaloric) [3]. Low-dimensional materials, mainly thin films, have recently attracted much interest for the promising applications. With respect to the bulk materials, they offer the further possibility of tuning properties by thickness [4] and by the choice of suitable substrates and underlayers [5]. The present paper is aimed at deepening these effects, also extending the study to laterally confined substrate-constrained and free-standing nanostructures.