Magnetoelasticity of Cr-Ga alloy single crystals at high pressures

Measurements are reported of the pressure dependences of the elastic consta nts of Cr+0.16 at. % Ga and Cr+0.88 at. % Ga alloy single crystals through the Neel temperature of both crystals and through the incommensurate-commen surate transition temperature of the latter crystal. The long-wavelength ac oustic-mode Gruneisen parameters, gp, which quantify the lattice vibrationa l anharmonicity, are calculated from the measurements. Both alloys show, de pending on the temperature, unusually large positive and negative values of gp which are ascribed to strong coupling of the spin-density wave to the a coustic phonons. The nature of these interactions differs for the two alloy s. (C) 1999 American Institute of Physics. [S0021-8979(99)57708-6].