Substrate Effects in Hysteresis of Microscale Ni-Mn-Sn Heusler Alloy Films

Abstract

During martensitic phase transformations in thin films, substrates impact hysteresis by introducing an additional interface, which can inhibit martensite/austenite interface motion. In order to reduce hysteresis, we examine 2.9-14.5 μm thick Ni-Mn-Sn films which in some cases have been delaminated from the substrates before or after annealing. We compare thermal hysteresis and defect densities at the interface. Delaminating films prior to annealing decreases hysteresis, whereas delaminating films after annealing does not significantly impact hysteresis. Substrate effects are attributed to the thermal expansion mismatch between the film and substrate, resulting in dislocations at the interface and consequentially, an increase in hysteresis.