Hysteresis and Phase Transition Kinetics in Magnetocaloric Materials

In the present paper, we review the recent research on the physics of magnetocaloric materials aiming to define a coherent theoretical framework in which hysteresis and kinetic effects can be appropriately discussed and interpreted in relation to intrinsic and extrinsic factors. We dedicate our efforts to introduce a thermodynamic description of the material, including the out-of-equilibrium aspects which are necessary to understand hysteresis, heat flux avalanches and thermal relaxation effects. In particular we show how intrinsic and extrinsic factors, contributing to define the energy landscape of the system, influence the resulting hysteresis and how different kinetic effects are expected depending on the phase transformation mechanisms, here described either as an out-of-equilibrium domain boundary motion or as a thermally activated process associated to energy barriers. Several applications of the theoretical models are discussed in relation with experiments on La(Fe-Si)(13)-based compounds and Mn-Bi.