Phase Diagram of the ${\rm Li_2O}$-${\rm V_2O_3}$-${\rm V_2O_5}$ System at 700 $^\circ$C: Correlations with Magnetic Defect Concentration in Heavy Fermion ${\rm LiV_2O_4}$

Polycrystalline samples of ${\rm LiV_2O_4}$ have been synthesized with magnetic defect concentrations $n$ ranging from 0.01 mol\% to 0.77 mol\% and average spins $S$ from 3/2 to 4. (1) Low-temperature $T$ magnetic susceptibility $\chi$ and magnetization $M$ versus applied magnetic field $H$ isotherms were measured to determine these $n$ and $S$ values. Here we report the phase diagram of the ${\rm Li_2O}$-${\rm V_2O_3}$-${\rm V_2O_5}$ ternary system at 700 $^\circ$C for compositions in equilibrium with ${\rm LiV_2O_4}$. This study provided a clarification of the synthesis conditions under which low and high magnetic defect concentrations can be obtained in ${\rm LiV_2O_4}$. The samples were prepared using conventional solid state reaction of appropriate amounts of ${\rm Li_2CO_3,\ V_2O_3}$ and ${\rm V_2O_5}$. $M(H)$ isotherms and $\chi(T)$ data were obtained on many of these samples. We confirmed that the ${\rm LiV_2O_4}$ phase can be obtained containing low (0.01 mol\%) to high ($\geq 0.5$ mol\%) magnetic defect concentrations and with consistently high defect $S$ values around 3 to 4. The highest $n$ values were obtained for ${\rm LiV_2O_4}$ samples in equilibrium with ${\rm V_2O_3}$ and the lowest values for ${\rm LiV_2O_4}$ samples in equilibrium with ${\rm V_3O_5}$, consistent with the results in Ref.\ (1).\\ (1) S. Kondo et al., PRL \textbf{78}, 3721 (1997); PRB \textbf {59}, 2609 (1999).