Phenomenological modeling of ferromagnetic shape memory alloys

A thermodynamically consistent phenomenological model is presented which captures the ferromagnetic shape memory effect, i.e. the large macroscopically observable shape change of magnetic shape memory materials under the application of external magnetic fields. In its most general form the model includes the influence of the microstructure for both the volume fraction of different martensitic variants and magnetic domains on the described macroscopic constitutive behavior. A phase diagram based approach is taken to postulate functions governing the onset and termination of the reorientation process. A numerical example is given for an experiment on on a NiMnGa single crystal specimen reported in the literature, for which the model is reduced to a two-dimensional case of an assumed magnetic domain structure.