Magnetoelasticity of Cr–Ga alloy single crystals at high pressures

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, [formula omitted] 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 [formula omitted] 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.