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

The preparative method, characterization, and magnetic susceptibility $\chi$ measurements versus temperature T of the heavy-fermion transition-metal oxide ${\mathrm{LiV}}_2{\mathrm{O}}_4$ are reported in detail. The intrinsic $\chi \mathrm{}\left(T\right)\mathrm{}$ shows a nearly T-independent behavior below $\sim 30$ K with a shallow broad maximum at $\approx 16$ K, whereas Curie-Weiss-like behavior is observed above $\sim 50–100$ K. Field-cooled and zero-field-cooled magnetization $M^{\mathrm{obs}}$ measurements in applied magnetic fields $H=10\mathrm{}-100$ 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 $\chi$ with realistic parameters. In the high-$T$ range, fits of $\chi \mathrm{}\left(T\right)\mathrm{}$ by the predictions of high-temperature series expansion calculations provide estimates of the V-V antiferromagnetic exchange coupling constant ${J/k}_{\mathrm{B}}\sim 20$ K, g factor $g\sim 2,$ and the T-independent susceptibility. Other possible models to describe the $\chi \mathrm{}\left(T\right)\mathrm{}$ are discussed. The paramagnetic impurities in the samples were characterized using isothermal $M^{\mathrm{obs}}\mathrm{}\left(H\right)\mathrm{}$ measurements with $0<H<~5.5$ T at 2–6 K. These impurities are inferred to have spin $S_{\mathrm{imp}}\sim 3/2–4,$ $g_{\mathrm{imp}}\sim 2,$ and molar concentrations of 0.01–0.8 %, depending on the sample.