Domain microstructure evolution in magnetic shape memory alloys: Phase-field model and simulation

A phase-field micromagnetic microelastic model is employed to simulate domain microstructure evolution in magnetic shape memory alloys. The simulations reveal that coupled motions of martensite twin boundaries and magnetic domain walls depend not only on the external magnetic field but also on internal domain configurations. It is shown that a twin boundary can continue its motion under a decreasing magnetic field or even reverse motion direction without changing magnetic field. The domain microstructure-dependent driving forces for the coupled motions of martensite twin boundaries and magnetic domain walls are analyzed; these explain the complex domain processes and resultant peculiar magnetomechanical behavior of magnetic shape memory alloys.