Exchange interactions and magnetocaloric effects of the Heusler alloys Ni-Mn-In-R (R= Fe, Co)

The magnetic interactions and magnetocaloric effects in Ni2Mn1.4In0.6-xRx (x = 0-0.2) (R = Fe, Co) Heusler alloys are investigated by the first-principles and Monte Carlo method. The ab initio calculations provide a basic understanding of the competition of ferromagnetic and antiferromagnetic interactions due to the chemical disorder of the alloy compositions. The thermodynamic properties including magnetization, specific heat and magnetic entropy change are calculated by the finite-temperature Monte Carlo simulations using the exchange couplings and magnetic moments from ab initio calculation as input parameters. The results show that the Fe or Co doping in Ni2Mn1.4In0.6 leads to an increase of magnetic moment and magnetic entropy change but a decrease of magnetic transition temperature with the increase in the Fe or Co contents. This indicates that the transition temperature and magnetocaloric properties of Ni2Mn1.4In0.6 alloy can be tuned by substituting In atom by Fe or Co with different contents.