Finite Size‐Effects in Martensite Microstructure of Magnetic Shape Memory Films

Magnetic shape memory alloys, owing to their multifunctional properties, are a promising material system for integration into microsystems. Their multifunctionality arises from the coexistence of ferroelasticity and ferromagnetism. While size-effects in ferromagnetic microstructure are well understood, corresponding experiments on the ferroelastic martensite microstructure are sparse. In this study, we use epitaxially grown Ni-Mn-Ga-based films as a model system to investigate the influence of finite size on the martensite microstructure under constrained and freestanding conditions. The results show that the microfabricated patterns, in both conditions, retain the characteristics of their continuous film microstructures. Film thickness has a strong influence, as this is the smallest extension investigated in our study. Our analysis reveals similarities and differences between finite size effects in ferromagnetic and ferroelastic microstructure, which is crucial for using these multifunctional materials in microsystems.