On the basis of Monte Carlo simulations using the Potts model Hamiltonian, we investigate the complex temperature dependence of magnetization of ferromagnetic $\text{Ni-Mn-}X$ $\left(X=\text{In},\text{Sn},\text{Sb}\right)$ Heusler alloys, in which part of the Mn atoms, which occupy the $X$ sites, interacts antiferromagnetically with the Mn atoms on the Mn sublattice. It is shown that this antiferromagnetic exchange is responsible for metamagnetic behavior and a series of magnetic phase transitions in the Heusler alloys. For an optimal choice of parameters of the model Hamiltonian, which have partially been obtained from ab initio calculations, we are able to describe the physics associated with the coupled martensitic-magnetic phase transition. The simulations lead to a qualitative agreement with the experimental magnetization curves and their dependence on temperature and composition.

• Received 3 June 2008

DOI:https://doi.org/10.1103/PhysRevB.78.184427