Phase structure evolution on Ni-Mn-Ga/Si (100) thin films: Effect of substrate temperature

This study investigated microstructure evolution, thermo-magnetic and mechanical behavior of magnetic shape memory thin film at different substrate temperature. X-ray diffraction measurements reveal the evolution of different phase structure concerning substrate temperature. According to microstructure analysis, the grain size increases with the substrate temperature and also the shape of the grain changed from pyramidal to spherical. A strong dependence of magnetic properties on grain size and phase structure is also observed. Coercivity is found to decrease with increasing substrate temperature up to a minimum value of 62 Oe for the film deposited at 773 K and with further increase in substrate temperature it is found to increase. Based on the relationship between grain size and the nanoindentation results, the decline in the hardness and elastic moduli can be reasonably inferred to be associated with enlarged grain size, consistent with the "Hall–Petch" effect and the grain refinement mechanism.