Field-induced strains of 6% were reported, in ferromagnetic martensites at room temperature, which were the result of a twin boundary motion that was driven largely by the Zeeman-energy difference across the twin boundary. The strain which was measured parallel to the applied magnetic field was negative for the sample/field geometry that was used here. The strain saturated in fields of the order of 400kA/m, and was blocked by a compressive stress of the order of 2MPa which was applied orthogonally to the magnetic field. The strain-versus-field curves exhibited an appreciable hysteresis which was associated with motion of the twin boundaries. A simple model could account quantitatively for the dependence of strain upon magnetic field and external stress.

6% Magnetic Field-Induced Strain by Twin-Boundary Motion in Ferromagnetic Ni-Mn-Ga. S.J.Murray, M.Marioni, S.M.Allen, R.C.O’Handley, T.A.Lograsso: Applied Physics Letters, 2000, 77[6], 886-8