Impacts of Gd doping on electronic structure， magnetism，and martensitic phase transition in Ni-Mn-In magnetic shape memory alloys： first-principles calculations and experiment

The impact of Gd doping on Ni-Mn-In alloys was investigated using a combination of experimental studies and first-principles calculations. The results of first-principles calculations reveal that Gd doping tends to occupy the sublattices of Ni and In in the Ni8Mn6In2 alloy. Gd substitution of either Ni or In increases the martensitic temperature and decreases the Curie temperature at the same time. In particular， the increase in phase transition temperature is more significant after Gd replaces In. The electron density of states analysis shows that Gd doping decreases the austenite stability and increases the martensite stability， which is the main reason for the increase in phase transition temperature. The Ni50-xMn35In15Gdx（x=0，1，2） and Ni50Mn35In15-xGdx（x=0，1，2） polycrystalline alloys are successfully prepared using a vacuum arc melting furnace， and analyzed by the DSC experimental data， it was observed that the doping of Gd enhances the phase transition temperature of alloy. Specifically， the martensitic transformation starts temperature of Ni50Mn35In13Gd2 reached 160 ℃， which can meet the high-temperature （≈97 ℃） operating conditions. The doping of a single Gd atom does not change the magnetic state of the alloy parent phases and martensitic phases in Ni-Mn-In alloys， resulting in a minor effect on the difference of magnetization. The mechanism of Gd doping affects the magnetic structure of the alloy is elucidated.