Heat Capacity of Vanadium Oxides at Low Temperature

Abstract

The electronic contribution to the heat capacity of ${\mathrm{V}}_{1.97}$${\mathrm{O}}_{3}$, ${\mathrm{V}}_{7}$${\mathrm{O}}_{13}$, and ${\mathrm{V}}_{\mathrm{O}.86}$${\mathrm{W}}_{0.14}$${\mathrm{O}}_{2}$ is very large, with $\ensuremath{\gamma}=(130\ifmmode\pm\else\textpm\fi{}3), (80\ifmmode\pm\else\textpm\fi{}5), \mathrm{and} (80\ifmmode\pm\else\textpm\fi{}5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ cal ${\mathrm{K}}^{\ensuremath{-}2}$/mole V, respectively. Comparison of effective masses calculated from the heat capacity, magnetic susceptibility, and optical properties suggests that the mass enhancement results mainly from spin fluctuations in a strongly correlated electron gas. The magnetic contribution to the entropy of ${\mathrm{V}}_{4}$${\mathrm{O}}_{7}$ at 53 K is 0.32 cal ${\mathrm{K}}^{\ensuremath{-}1}$/mole V.