Ehrenfest relations and magnetoelastic effects in field-induced ordered phases

TL;DR

This paper develops a Ginzburg-Landau theoretical framework to analyze magnetoelastic effects and Ehrenfest relations in field-induced magnetic ordered phases, predicting how elastic constants vary with magnetic field, pressure, and temperature.

Contribution

It introduces a theoretical model linking magnetoelastic properties with phase diagrams and Ehrenfest relations in field- and pressure-induced magnetic phases.

Findings

Elastic constant decreases discontinuously at critical field Hc.

Elastic constant decreases linearly with magnetic field in the ordered phase.

Derived Ehrenfest relation connects elastic constant changes with pressure dependence of Hc.

Abstract

Magnetoelastic properties in field-induced magnetic ordered phases are studied theoretically based on a Ginzburg-Landau theory. A critical field for the field-induced ordered phase is obtained as a function of temperature and pressure, which determine the phase diagram. It is found that magnetic field dependence of elastic constant decreases discontinuously at the critical field, Hc, and that it decreases linearly with field in the ordered phase (H>Hc). We found an Ehrenfest relation between the field dependence of the elastic constant and the pressure dependence of critical field. Our theory provides the theoretical form for magnetoelastic properties in field- and pressure-induced ordered phases.