Thermodynamics of a model solid with magnetoelastic coupling

TL;DR

This paper investigates the thermodynamics of a magnetoelastic solid model, analyzing how magnetic and elastic properties interact under external magnetic fields and pressure, with detailed calculations of entropy, specific heat, and magnetocaloric effects.

Contribution

It introduces a self-consistent Gibbs energy-based framework to study magnetoelastic coupling effects in a mean-field ferromagnetic system with realistic lattice interactions.

Findings

Magnetoelastic coupling significantly influences thermodynamic properties.

External magnetic field alters entropy and specific heat.

Magnetocaloric effects are characterized under pressure variations.

Abstract

In the paper a study of a model magnetoelastic solid system is presented. The system of interest is a mean-field magnet with nearest-neighbour ferromagnetic interactions and the underlying s.c. crystalline lattice with the long-range Morse interatomic potential and the anharmonic Debye model for the lattice vibrations. The influence of the external magnetic field on the thermodynamics is investigated, with special emphasis put on the consequences of the magnetoelastic coupling, introduced by the power-law distance dependence of the magnetic exchange integral. Within the fully self-consistent, Gibbs energy-based formalism such thermodynamic quantities as the entropy, the specific heat as well as the lattice and magnetic response functions are calculated and discussed. To complete the picture, the magnetocaloric effect is characterized by analysis of the isothermal entropy change and the adiabatic temperature change in the presence of the external pressure.