Theoretical Study of Magnetic Properties and Multiple Twin Boundary Motion in Heusler Ni-Mn-X Shape Memory Alloys Using First Principles and Monte Carlo Method

In this paper we firstly propose and study a microscopic model of multiple twin boundary motion using the first principles and Monte Carlo simulations in Heusler Ni-Mn-X (for example, X = Ga) alloys on real tetragonal lattice. The two variants of the low temperature martensite which divided by twin boundary are considered. The Heisenberg model for magnetic subsystem and Blume-Emery-Griffiths (BEG) one for structural subsystem with magnetostructural interaction between these subsystems are used. The influence of external magnetic field and anisotropy on the twin boundary motion is studied. It is shown that proposed model gives the picture of twin boundary motion as in experiments.