Stress-induced magnetization in polycrystalline Ni-Fe-Ga ferromagnetic shape memory alloy

Results are reported for simultaneous experimental studies of the stress-induced magnetic induction and of anelasticity in a polycrystalline Ni-Fe-Ga ferromagnetic shape memory alloy. The authors found in the martensitic state a linear relationship between mechanically induced induction and stress amplitude, in contrast to a strong nonlinearity of the anelastic strain. This difference between elastic and magnetic responses to applied stress points to inefficient coupling between the motion of elastic twins/domain boundaries and magnetic domain walls. They argue that, in acoustic experiments, magnetic domain walls in Ni-Fe-Ga polycrystals perform only linear displacements within local potential minima, characteristic for the microeddy current magnetomechanical damping. (C) 2007 American Institute of Physics.