Specific heat (1.2{endash}108 K) and thermal expansion (4.4{endash}297 K) measurements of the 3d heavy-fermion compound LiV{sub 2}O{sub 4}

Specific heat C{sub p}(T) measurements of the heavy-fermion normal-spinel structure compound LiV{sub 2}O{sub 4} were carried out using a heat-pulse calorimeter over the temperature {ital T} range from 1.2 to 108 K. The electronic specific heat C{sub e}(T) of LiV{sub 2}O{sub 4} is extracted from the C{sub p}(T) data using the lattice contribution obtained for LiTi{sub 2}O{sub 4}, a superconductor with T{sub c}=11.8 K. The electronic specific heat coefficient {gamma}(T){equivalent_to}C{sub e}(T)/T of LiV{sub 2}O{sub 4} is found to be 0.42 and 0.43 J/mol K{sup 2} at T=1 K for two different high-magnetic-purity samples, respectively. {gamma}(T) decreases rapidly with increasing temperature from 4 to 30 K and then decreases much more slowly from 0.13 J/molthinspK{sup 2} at 30 K to 0.08 J/mol K{sup 2} at 108 K. The C{sub e}(T) of the first of the above two LiV{sub 2}O{sub 4} samples is compared with theoretical predictions for the spin S=1/2 Kondo model, a generic Fermi liquid model, and an antiferromagnetically coupled quantum-disordered metal. Each of these theories can adequately describe the {ital T} dependence of C{sub e} in the Fermi liquid regime at low ({approximately}1{endash}10 K) temperatures, consistently yielding a large extrapolated {gamma}(0)=428(3) mJ/mol K{sup 2}. However, none of these theoriesmore » describes C{sub e}(T) from {approximately}10 K to 108 K. Our C{sub e}(T) data are also in severe disagreement with the magnetic specific heat of the spin S=1/2 Heisenberg model, calculated above {approximately}40 K for the V sublattice of the spinel structure. Thermal expansion measurements of LiV{sub 2}O{sub 4} were carried out from 4.4 to 297 K using a differential capacitance dilatometer. Strong increases in the thermal expansion coefficient and Gr{umlt u}neisen parameter {Gamma} are found below {approximately}20 K, confirming the results of Chmaissem {ital et al.} [Phys. Rev. Lett. {bold 79}, 4866 (1997)] obtained using neutron diffraction. We estimate {Gamma}(0){approx}11.4, which is intermediate between those of conventional metals and {ital f}-electron heavy-fermion compounds. {copyright} {ital 1999} {ital The American Physical Society}« less