Large magnetic entropy change associated with the weakly first-order paramagnetic to ferrimagnetic transition in antiperovskite manganese nitride CuNMn3.

We report a systematic study of the specific heat and dc magnetic susceptibility on the paramagnetic to ferrimagnetic transition (TC~141 K) in CuNMn3. A large magnetocaloric effect (MCE) at TC is observed with the entropy change of 3.49 J/kg K (6.38 J/kg K) for the field change of ΔH=20 kOe (45 kOe). The analysis of the isothermal magnetizations, including the derived Arrott plots and magnetic entropy change, shows a second-order like transition at TC. However, the existence of latent heat around TC is unambiguously manifested by the reduced slope of the temperature-time relaxations recorded during the specific heat measurement, indicating the transition is in fact weakly first-order in nature. The large MCE comparable with those observed the antiperovskite manganese carbides suggests it is equivalently interesting to explore the MCE in the antiperovskite manganese nitrides as in the carbides. [ABSTRACT FROM AUTHOR]