The effect of pressure and temperature on the Raman-active phonon mode of osmium metal has been investigated for pressures up to 20 GPa and temperatures in the range 10--300 K. Under hydrostatic conditions (He pressure medium) the phonon frequency increases at a rate of 0.73(5) cm^{-1}/GPa (T = 300 K). A large temperature-induced and wavelength-dependent frequency shift of the phonon frequency is observed, of which only a small fraction can be associated with the thermal volume change. The main contribution to the temperature dependence of the phonon frequency is rather attributed to non-adiabatic effects in the electron-phonon interaction, which explains also the observation of an increasing phonon line width upon cooling. The phonon line width and the pressure-induced frequency shift were found to be unusually sensitive to shear stress.
@article{arxiv.cond-mat/0503272,
title = {Raman scattering in osmium under pressure},
author = {Yu. S. Ponosov and I. Loa and V. E. Mogilenskikh and K. Syassen},
journal= {arXiv preprint arXiv:cond-mat/0503272},
year = {2009}
}