Magnetoelasticity of Cr–Ga alloy single crystals at high pressures

Abstract

Measurements are reported of the pressure dependences of the elastic constants of Cr+0.16 at. % Ga and Cr+0.88 at. % Ga alloy single crystals through the Néel temperature of both crystals and through the incommensurate–commensurate transition temperature of the latter crystal. The long-wavelength acoustic-mode Grüneisen parameters, γp, which quantify the lattice vibrational anharmonicity, are calculated from the measurements. Both alloys show, depending on the temperature, unusually large positive and negative values of γp which are ascribed to strong coupling of the spin-density wave to the acoustic phonons. The nature of these interactions differs for the two alloys.