Caloric properties of materials near a tricritical point

We present a mean-field study of caloric effects driven by primary and secondary fields near tricritical points, which are fields thermodynamically conjugated to the main and secondary order parameters, respectively. General features, such as critical exponents and their crossover from critical to tricritical behaviours, are studied by means of a generic free energy Landau expansion. To deal with specific materials, we propose a model that combines the Blume-Emery-Griffiths prototype to study tricritical points with the Bean-Rodbell approach to include magnetovolume effects. In this model the primary field is the magnetic field, while chemical and mechanical pressures are secondary fields. In spite of the scarcity of experimental data, we have shown that results for the La(FeₓSi₁₋ₓ)₁₃ and MnSi compounds are in good agreement with our predictions. We expect that our results will motivate and guide new experimental research aiming at optimizing caloric materials.