Modelling shape-memory effects in ferromagnetic alloys

Abstract

We develop a combined Ginzburg–Landau/micromagnetic model dealing with conventional and magnetic shape-memory properties in ferromagnetic shape-memory materials. The free energy of the system is written as the sum of structural, magnetic and magnetostructural contributions. We first analyse a mean field linearized version of the model that does not take into account long-range terms arising from elastic compatibility and demagnetization effects. This model can be solved analytically and in spite of its simplicity allows us to understand the role of the magnetostructural term in driving magnetic shape-memory effects. Numerical simulations of the full model have also been performed. They show that the model is able to reproduce magnetostructural microstructures reported in magnetic shape-memory materials such as Ni2MnGa as well as conventional and magnetic shape-memory behaviour.