Caloric properties of materials near a tricritical point

TL;DR

This study models caloric effects near tricritical points using a Landau expansion and a combined Blume-Emery-Griffiths and Bean-Rodbell approach, providing predictions aligned with limited experimental data.

Contribution

It introduces a comprehensive theoretical framework for caloric effects near tricritical points, integrating primary and secondary fields with specific material models.

Findings

Predicted caloric behavior matches experimental data for La(Fe$_{x}$Si$_{1-x}$)$_{13}$ and MnSi.

Analyzed critical exponents and crossover behaviors near tricritical points.

Provided guidance for experimental optimization of caloric materials.

Abstract

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(Fe$_{x}$Si$_{1-x}$)$_{13}$ 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.