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

D. C. Johnston, C. A. Swenson, S. Kondo
1999 Physical Review B (Condensed Matter)  
Specific heat C_p(T) measurements of the heavy fermion normal-spinel structure compound LiV_2O_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_e(T) of LiV_2O_4 is extracted from the C_p(T) data using the lattice contribution obtained for LiTi_2O_4, a superconductor with T_c = 11.8 K. The electronic specific heat coefficient γ(T) = C_e(T)/T of LiV_2O_4 is found to be 0.42 and 0.43 J/mol K^2 at T = 1 K for two
more » ... nt high magnetic purity samples, respectively. γ(T) decreases rapidly with increasing temperature from 4 to 30 K and then decreases much more slowly from 0.13 J/mol K^2 at 30 K to 0.08 J/mol K^2 at 108 K. The C_e(T) 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 C_e(T) in the Fermi liquid regime at low ( 1 to 10 K) temperatures, consistently yielding a large extrapolated γ(0) = 428(3) mJ/mol K^2. However, none of these theories describes C_e(T) from 10 K to 108 K. Our C_e(T) data are also in severe disagreement with the magnetic specific heat of the spin S = 1/2 Heisenberg model. Thermal expansion measurements of LiV_2O_4 were carried out from 4.4 to 297 K using a differential capacitance dilatometer. Strong increases in the thermal expansion coefficient and Grüneisen parameter Γ are found below 2̃0 K, confirming the results of Chmaissem et al. [Phys. Rev. Lett. 79, 4866 (1997)] obtained using neutron diffraction. We estimate that Γ(0) is about 11.4.
doi:10.1103/physrevb.59.2627 fatcat:j6ishw22sbaslhhbvc6oajfokm