Magnetic shape memory alloys, which transform martensitically below the Curie temperature in the ferromagnetic state, represented a new class of actuators. In Ni2MnGa, unusually large magnetic field-induced strains of about 10% were observed. This effect was related to a high mobility of martensitic twin boundaries in connection with a large magneto-crystalline anisotropy. Magnetic shape memory materials existed in a variety of different martensitic structures depending upon temperature and composition. The energetics of L10 phase twin boundary motion were investigated quasi-statically using ab initio methods and the results were related to calculations of the magneto-crystalline anisotropy energy. The results indicated that, for the L10 structure, the energy needed for a coherent shift of a twin boundary could be too large to be overcome solely by magnetic field-induced strains.

Ab initio Investigation of Twin Boundary Motion in the Magnetic Shape Memory Heusler Alloy Ni2MnGa. M.E.Gruner, P.Entel, I.Opahle, M.Richter: Journal of Materials Science, 2008, 43[11], 3825-31