Prediction of realistic entropy behavior from mixed state magnetization data for first order phase transition materials

We present here the influence of the phase transformation on the magnetic and magnetocaloric properties of a typical first order system (MnAs) having mixed-phase state near the transition temperature. We use chemical doping to introduce various field and temperature dependent thermodynamic functions into the system. From the nature of the phase transformation with different thermodynamics and the magnetic entropy behavior treating Maxwell's relation on magnetization data, we modeled the mixed-phase state of the system with magnetization. This lead to distinguish the contribution of entropy influenced by phase transformation obtained from incorrect application of Maxwell's relation on the nonequilibrium system and mixed state and a realistic entropy value can be obtained subjected to simple correction to the experimental nonequilibrium magnetization data and using Maxwell's relation. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3356007]