Brillouin scattering of V2O5 and Sn-intercalated V2O5

Abstract

The Brillouin scattering spectra of $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{V}}_{2}{\mathrm{O}}_{5}$ and Sn-intercalated ${\mathrm{V}}_{2}{\mathrm{O}}_{5}$ (${\mathrm{Sn}}_{0.07}{\mathrm{V}}_{2}{\mathrm{O}}_{5}$) were measured for sound propagation directions at and near the [001] direction, which is normal to the van der Waals gaps in this layered material. Anisotropic sound velocities and stiffness tensor elements ${c}_{ij}$ were determined from the Brillouin frequency shifts. Measurements for propagation in the [001] direction in pure ${\mathrm{V}}_{2}{\mathrm{O}}_{5}$ yielded ${c}_{33}=42.20\phantom{\rule{4pt}{0ex}}\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0.16em}{0ex}}0.38\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$, ${c}_{44}=23.55\phantom{\rule{4pt}{0ex}}\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0.16em}{0ex}}0.27\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$, and ${c}_{55}=25.65\phantom{\rule{4pt}{0ex}}\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0.16em}{0ex}}0.27\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$ showing substantial disagreement with some published theoretical calculations. High longitudinal stiffness values $\ensuremath{\sim}230\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$ in the [100] and [010] directions correspond to remarkably high longitudinal sound velocities of 8290 m/s, demonstrating strong anisotropy associated with the layered structure. ${\mathrm{Sn}}_{0.07}{\mathrm{V}}_{2}{\mathrm{O}}_{5}$ was found to have stiffnesses of ${c}_{33}=43.72\phantom{\rule{4pt}{0ex}}\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0.16em}{0ex}}0.23\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$, ${c}_{44}=22.91\phantom{\rule{4pt}{0ex}}\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0.16em}{0ex}}0.20\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$, and ${c}_{55}=26.54\phantom{\rule{4pt}{0ex}}\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0.16em}{0ex}}0.22\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$, indicating that some deformation modes are slightly stiffened while others may be unaffected or even softened by the intercalant.