Magnetic interactions and electronic structure of Ni-Mn-In

The electronic structure and magnetic properties of a magnetic shape memory alloy Ni-Mn-In have been studied using spin polarized fully relativistic Korringa-Kohn-Rostoker (SPRKKR) method. The total energy calculations with different starting magnetic spin configurations show that the ground state of Ni2Mn1.4In0.6 is ferromagnetic. The spin and orbital magnetic moments of Ni2Mn1.4In0.6 and Ni2MnIn are in good agreement with the magnetization measurements. The exchange coupling parameters of the different sublattice interactions exhibit a strong competition between ferromagnetic and antiferromagnetic configurations, due to the substitution of excess Mn atoms at the In site in Ni2Mn1.4In0.6. The Curie temperature of Ni2MnIn, calculated under a mean field approximation, is found to be in relatively good agreement with the experimental values. While Ni2MnIn does not undergo martensite transition, it is shown that a Jahn-Teller splitting of the Ni 3d eg states plays an important role in driving the martensite transformation in Ni2Mn1.4In0.6. We find that both the calculated ultra-violet photoemission spectra and the inverse photoemission spectra are in good agreement with the existing experimental data.