Magnetic and transport properties of the mixed valent vanadium oxides LuV$_4$O$_8$ and YV$_4$O$_8$*

Mixed valent vanadium oxides have been subjects of wide interest owing to their exotic properties such as heavy fermion behavior below 10 K in spinel LiV$_2$O$_4$ and isosymmetrical phase transition and charge ordering in YbV$_4$O$_8$. \textit{L}V$_4 $O$_8$ (\textit{L} = Y, Lu) crystallize in a structure similiar to that of orthorhombic CaFe$_2$O$_4$, containing four inequivalent V sites arranged in zig-zag chains. The formal oxidation state of V in these compounds is 3.25. In this study, the magnetic and transport properties of these \textit{L}V$_4 $O$_8$ compounds are reported. The magnetic susceptibility indicates two possible structural phase transitions in YV$_4$O$_8 $ in the temperature ($T$) range 70--90 K\@. Anomalies in the heat capacity are also seen in this temperature range. The zero- field-cooled/field-cooled magnetic susceptibilities show possible canted antiferromagnetic ordering in both YV$_4$O$_8$ and LuV$_4$O$_8$ for $T < 50$~K\@. For LuV$_4$O$_8$, the dc electrical resistivity of a sintered pellet measured using a standard four-probe technique shows a strong increase at $T < 100 $~K\@.