Dynamic observation of Joule heating-induced structural and domain transformation in smart shape-memory alloy

Ferromagnetic shape-memory alloys can realize smart functional sensors and actuators due to their distinctive capabilities of field-induced strain, which have attracted extensive interests. However, their response and transformation kinetics under the stimulus of Joule heating are still lack, which limits their extensive application into electrical-related sensors. In this work, we firstly report the dynamic structural transformation and magnetic domain evolution of smart shape memory alloy induced by Joule heating in-situ TEM with thermoelectric holder by using Ni2MnGa as experimental model. The stimulus of low-power Joule heating induces the reversible structural and magnetic domain transformations of the smart Ni2MnGa shape memory alloy. Whilst, high-power Joule heating induces an irreversible process of structural transformation and magnetic domain evolution. Our work should be significant to expand the smart shape memory alloy into electrical-related applications.