Structural and Magnetic Properties of Magnetic Shape Memory Alloys on Ni-Mn-Co-In Self-standing Films

Ni-Mn-In films containing cobalt were deposited on a poly-vinyl alcohol (PVA) substrate using a dual magnetron sputtering apparatus with Ni45Mn40In15 and Co targets. The RF power for the Ni-Mn-In target was kept at 200 W, and the DC power for the cobalt target was 8 W. The thicknesses of the deposited films were 1 and 5 µm. After deposition, the films were annealed at 1123 K for 3.6 ks for 1 µm and 1023 K for 3.6 ks + 1173 K for 3.6 ks for 5 µm. The crystallinity of the films was affected by the heat treatment, and the films showed layered structures, such as 10M- and 14M-type structures. The martensitic transformation and magnetic phase transition influence each other, and both have a magnetic field dependence. In particular, the 5 µm film shows a metamagnetic phase transition with small transition temperature hysteresis. The magnetization experiments for the 5 µm film reveal a drastic magnetization change ΔM of 26 emu/g at 0.05 T and a martensitic transformation finish temperature change ΔM f of −8.5 K at 5 T.