Phase transformations in sputtered Ni–Mn–Ga magnetic shape memory alloy thin films

Abstract

Ni–Mn–Ga magnetic shape memory alloy films have been prepared by the DC magnetron sputtering technique. As-deposited films show a quasi-amorphous structure that crystallizes at ~500K. Crystallization study using Kissinger's analysis reveals a relatively low activation energy indicating partial crystallinity in the films. In situ X-ray diffraction studies show reversible martensite phase transformations, and phase segregation to non-transforming L12 precipitates at higher temperatures. It was observed that the phase segregation can be suppressed by low temperature heat treatment.