Quaternary Ni–Mn–In–Y Heusler alloys: a way to achieve materials with better magnetocaloric properties?

Abstract

The influence of nonmagnetic impurities (Y) on the magnetocaloric effect (MCE) in the Heusler alloy Ni50Mn34In16Y in which ferromagnetic and antiferromagnetic coupling coexists in the martensitic state is investigated by means of ab initio and Monte Carlo simulations. Different impurity configurations are considered. Either Mn on the Mn sublattice or Ni on the Ni sublattice is substituted randomly by Y or substitution may occur simultaneously on both sublattices. The magnetic and magnetocaloric properties are obtained as a function of temperature and magnetic field using a mixed type of Potts and Blume–Emery–Griffiths model where the model parameters are obtained from ab initio calculations. When varying the impurity concentration, the shape of the magnetization curves is drastically changed at the martensitic transformation temperature due to the complex competing magnetic interactions. We show that the inverse MCE effect increases if Mn is substituted by Y compared with Y substituting for Ni. For example, the alloy system Ni50Mn32.75Cu1.25In16 where 5 at% Mn is replaced by Cu exhibits an inverse MCE which is twice as large compared with Ni50Mn34In16. Such predictive simulations may be used to design Heusler composites which display larger MCEs.