Doping effect on orthorhombic Sr2VO4 with s=12 dimers

We studied single crystals of orthorhombic ${\mathrm{Sr}}_{2}{\mathrm{VO}}_{4}$ containing spin-singlet dimers of ${\mathrm{V}}^{4+}\phantom{\rule{0.28em}{0ex}}(3{d}^{1})$ and those with Ti or Nb substituted for V. We found that both Ti and Nb dopings induce the evolution of a Curie-Weiss component in the magnetic susceptibility, but the rate of evolution with doping is several times higher for Nb doping. We also found that Nb doping induces the conduction of $d$ electrons. These results can be explained by the hybridization of the Nb $4d$ states with the $3d$ states of the neighboring V ions, possibly causing rearrangement of the $d$ electron in the doubly degenerate $e$ states in the V ion.