Specific heat (1.2–108 K) and thermal expansion (4.4–297 K) measurements of the3dheavy-fermion compoundLiV2O4

Specific heat $C_{\mathrm{p}}\mathrm{}\left(T\right)\mathrm{}$ measurements of the heavy-fermion normal-spinel structure compound ${\mathrm{LiV}}_2{\mathrm{O}}_4$ were carried out using a heat-pulse calorimeter over the temperature T range from 1.2 to 108 K. The electronic specific heat $C_{\mathrm{e}}\mathrm{}\left(T\right)\mathrm{}$ of ${\mathrm{LiV}}_2{\mathrm{O}}_4$ is extracted from the $C_{\mathrm{p}}\mathrm{}\left(T\right)\mathrm{}$ data using the lattice contribution obtained for ${\mathrm{LiTi}}_2{\mathrm{O}}_4,$ a superconductor with $T_{\mathrm{c}}=11.8\mathrm{}$ K. The electronic specific heat coefficient $\gamma \mathrm{}\left(T\right)\mathrm{}\equiv C_{\mathrm{e}}\mathrm{}\left(T\right)/T$ of ${\mathrm{LiV}}_2{\mathrm{O}}_4$ is found to be 0.42 and $0.43\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}\hspace{0.5em}{\mathrm{K}}^2$ at $T=1\mathrm{}$ K for two different high-magnetic-purity samples, respectively. $\gamma \mathrm{}\left(T\right)\mathrm{}$ decreases rapidly with increasing temperature from 4 to 30 K and then decreases much more slowly from $0.13{\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{}\mathrm{K}}^2$ at 30 K to $0.08\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}\hspace{0.5em}{\mathrm{K}}^2$ at 108 K. The $C_{\mathrm{e}}\mathrm{}\left(T\right)\mathrm{}$ of the first of the above two ${\mathrm{LiV}}_2{\mathrm{O}}_4$ samples is compared with theoretical predictions for the spin $S=1/2\mathrm{}$ Kondo model, a generic Fermi liquid model, and an antiferromagnetically coupled quantum-disordered metal. Each of these theories can adequately describe the T dependence of $C_{\mathrm{e}}$ in the Fermi liquid regime at low (∼1–10 K) temperatures, consistently yielding a large extrapolated $\gamma \mathrm{}\left(0\right)=428\mathrm{}\left(3\right)\mathrm{}\mathrm{m}\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}\hspace{0.5em}{\mathrm{K}}^2.$ However, none of these theories describes $C_{\mathrm{e}}\mathrm{}\left(T\right)\mathrm{}$ from