First-principles study of the structural and magnetic properties of the Ni45Co5Mn39Sn11 Heusler alloy

The structural and magnetic properties of Co-doped Ni-Mn-Sn Heusler alloy are investigated in the framework of density functional theory and Monte Carlo method. The first principles calculations of the equilibrium properties (crystalline structure and magnetic ordering) indicate that the ferromagnetic state is favorable in the austenite structure, whereas the ferrimagnetic order is stable in the martensite structure. The strong competition of ferro- and antiferromagnetic exchange interactions is arising from the austenite-martensite crossover. The temperature dependences of total magnetization and isothermal entropy and adiabatic temperature changes (magnetocaloric effect) are calculated by means of proposed Hamiltonian model with the ab initio magnetic exchange couplings and magnetostructural interrelation. The calculated properties are in good agreement with experimental ones.