Ab Initio and Monte Carlo Approaches For the Magnetocaloric Effect in Co- and In-Doped Ni-Mn-Ga Heusler Alloys

摘要: The complex magnetic and structural properties of Co-doped Ni-Mn-Ga Heusler alloys have been investigated by using a combination first-principles calculations classical Monte Carlo simulations. We restricted the investigations to systems with 0, 5 9 at% Co. Ab initio show presence ferrimagnetic order austenite martensite depending on composition, where excess Mn atoms Ga sites reversed spin configurations. Stable is found for 0 (5) Co ac=a ratio 1.31 (1.28), respectively, leading strong competition ferro- antiferro-magnetic exchange interactions between nearest neighbor atoms. simulations ab coupling constants as input parameters allow one discuss behavior at finite temperatures determine transition temperatures. Curie temperature increase Co, while decreases increasing content. This can be attributed stronger Co-Mn, Mn-Mn Mn-Ni in compared corresponding ones martensite. crossover from direct inverse magnetocaloric effect due substitution Ni leads appearance "paramagnetic gap" martensitic phase. Doping In increases jump temperature. simulated Co- In-doped are good qualitative agreement available experimental data.