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On the inverse and conventional magnetocaloric effects in MnRhAs single crystals

We report on the magnetic and magnetocaloric properties of a MnRhAs single crystal. The ternary arsenide exhibits a rather complex magnetic behaviour. A first order metamagnetic type transition from antiferromagnetic (AFI) to ferromagnetic (F) states takes place at Tt ~ 158 K, and a second order transition from ferromagnetic (F) to antiferromagnetic (AFII) states occurs at TC ~196 K, the paramagnetic state occurring at T > TN = 238 K. Magnetic entropy changes were calculated using, Maxwell relation and Clausius-Clapeyron equation. Both approaches are compared and discussed. The AFI-F transition in MnRhAs gives rise to an interestingly high level of negative magnetocaloric effect. Under a field change 0-1 T, the maximum magnetic entropy variation is about 3 J/kg K. For sufficiently high enough magnetic fields, the magnetocaloric working temperature range below 158 K can be covered. The F-AFII transition is accompanied by a relatively modest MCE (-2.3 J/kg K for 5 T at TC = 196 K), but it improves the working temperature span as well as the magnetocaloric properties. A minimum estimated refrigerant capacity of about 900 J/kg can be provided by a MnRhAs single crystal compound