Low-energy spin fluctuations in the metallic spinel compound LiV_2O_4

摘要

In the family of transition metal oxides the spinel compound LiV_2O_4 is a rare metallic system showing heavy fermion behavior. In particular, an anomalously large specific heat coefficient γ= C/T and strongly enhanced magnetic susceptibility χ_S were detected in the low temperature limit, T < 30K . Recently we have proposed a model which allowed us to relate such an anomalous behavior of LiV_2O_4 to the proximity of the underlying 3d-electron system to a magnetic instability at T 0. The emergence of a rather peculiar paramagnetic ground state with largely degenerate low-energy "critical" antiferromagnetic fluctuations in LiV_2O_4 is the combined effect of strong electron correlations and the geometrical frustration of V-ion pyrochlore lattice forming the metallic system in this compound. A self-consistent renormalization theory was developed to describe effects of strong coupling between spin fluctuation modes and their evolution with varying temperature and external pressure. The theory was shown to provide a firm basis for understanding many peculiar properties of spin dynamics obtained in the inelastic neutron scattering and NMR measurements on LiV_2O_4.