Thermodynamics of Multiferroic Materials

Abstract

This chapter deals with the Thermodynamics of multiferroic materials. We first discuss the symmetry of the four primary ferroic order parameters related to ferromagnets, ferroelectrics, ferroelastics and ferrotoroidics and set up basic field equations. We then develop a general thermodynamic description based on generalized displacements and the corresponding conjugated fields. We use these ideas to calculate multicaloric effects in these materials, in particular focussing on the toroidocaloric effect. Next we develop Landau free energy models for multiferroic materials and illustrate various ideas through three representative examples: (i) magnetoelectric transitions, (ii) magnetic shape memory transitions where elasticity plays a crucial role, and (iii) ferrotoroidic transitions. We also briefly discuss the role of disorder and its consequences for the existence of ferroic tweed as well as ferroic glass. Finally, we provide an outlook in terms of the open problems in this exciting field of research. © Springer-Verlag Berlin Heidelberg 2014.