Synthesis, characterization, and magnetic susceptibility of the heavy-fermion transition-metal oxideLiV2O4

Abstract

The preparative method, characterization, and magnetic susceptibility $\ensuremath{\chi}$ measurements versus temperature T of the heavy-fermion transition-metal oxide ${\mathrm{LiV}}_{2}{\mathrm{O}}_{4}$ are reported in detail. The intrinsic $\ensuremath{\chi}(T)$ shows a nearly T-independent behavior below $\ensuremath{\sim}30$ K with a shallow broad maximum at $\ensuremath{\approx}16$ K, whereas Curie-Weiss-like behavior is observed above $\ensuremath{\sim}50--100$ K. Field-cooled and zero-field-cooled magnetization ${M}^{\mathrm{obs}}$ measurements in applied magnetic fields $H=10\ensuremath{-}100$ G from 1.8 to 50 K showed no evidence for spin-glass ordering. Crystalline electric field theory for an assumed cubic V point group symmetry is found insufficient to describe the observed temperature variation of the effective magnetic moment. The Kondo and Coqblin-Schrieffer models do not describe the magnitude and T dependence of $\ensuremath{\chi}$ with realistic parameters. In the high-$T$ range, fits of $\ensuremath{\chi}(T)$ by the predictions of high-temperature series expansion calculations provide estimates of the V-V antiferromagnetic exchange coupling constant ${J/k}_{\mathrm{B}}\ensuremath{\sim}20$ K, g factor $g\ensuremath{\sim}2,$ and the T-independent susceptibility. Other possible models to describe the $\ensuremath{\chi}(T)$ are discussed. The paramagnetic impurities in the samples were characterized using isothermal ${M}^{\mathrm{obs}}(H)$ measurements with $0<H<~5.5$ T at 2--6 K. These impurities are inferred to have spin ${S}_{\mathrm{imp}}\ensuremath{\sim}3/2--4,$ ${g}_{\mathrm{imp}}\ensuremath{\sim}2,$ and molar concentrations of 0.01--0.8 %, depending on the sample.