Thermodynamic model of a solid with RKKY interaction and magnetoelastic coupling

TL;DR

This paper develops a comprehensive thermodynamic model of a solid incorporating RKKY magnetic interactions and magnetoelastic coupling, providing insights into phase behavior and thermal expansion properties.

Contribution

It introduces a self-consistent thermodynamic framework for a magnetoelastic system with long-range RKKY and direct exchange interactions, applied to FCC structures.

Findings

Prediction of negative thermal expansion coefficient in certain antiferromagnetic phases

Numerical calculation of thermodynamic functions under various external conditions

Derivation of generalized Gibbs potential and equations of state

Abstract

Thermodynamic description of a model system with magnetoelastic coupling is presented. The elastic, vibrational, electronic and magnetic energy contributions are taken into account. The long-range RKKY interaction is considered together with the nearest-neighbour direct exchange. The generalized Gibbs potential and the set of equations of state are derived, from which all thermodynamic functions are self-consistently obtained. Thermodynamic properties are calculated numerically for FCC structure for arbitrary external pressure, magnetic field and temperature, and widely discussed. In particular, for some parameters of interaction potential and electron concentration corresponding to antiferromagnetic phase, the existence of negative thermal expansion coefficient is predicted.