Martensitic Transformation in Ni-Mn-Ga Thin Films Deposited on Alumina

Ni-Mn-Ga magnetic shape memory alloys (MSMAs) tend to undergo a large, reversible deformation upon the application of a magnetic field. This deformation is attributed to twin boundary motion in the martensitic phase. In an effort to utilize the magneto-mechanical behavior of Ni-Mn-Ga polycrystalline thin films for micro-sensors and actuators, the behavior of Ni- Mn-Ga thin films is paid a great attention last few years. Substrate curvature measurements on Ni-Mn-Ga films, deposited on Al2O3 ceramics, were performed. The martensitic transformation in the film is manifested by an anomalous stress change accompanied by thermal hysteresis. The stress-curvature experiments display a stress relaxation during the martensitic transformation of approximately 30–100 MPa, depending on film thickness