Possible magnetic order and suppression of superconductivity by V doping in Sr2VO3FeAs

Superconductivity at 33 K in ${\text{Sr}}_{2}{\text{VO}}_{3}\text{FeAs}$ is completely suppressed by small amounts of V doping in ${\text{Sr}}_{2}{\text{VO}}_{3}({\text{Fe}}_{0.93(\ifmmode\pm\else\textpm\fi{}0.01)}{\text{V}}_{0.07(\ifmmode\pm\else\textpm\fi{}0.01)})\text{As}$. The crystal structures and exact stoichiometries are determined by combined neutron powder diffraction and x-ray powder diffraction. ${\text{Sr}}_{2}{\text{VO}}_{3}\text{FeAs}$ is shown to be very sensitive to Fe/V mixing, which interferes with or even suppresses superconductivity. This inhomogeneity may be intrinsic and explains scattered reports regarding ${T}_{c}$ and reduced superconducting phase fractions in ${\text{Sr}}_{2}{\text{VO}}_{3}\text{FeAs}$. Neutron-diffraction data collected at 4 K indicate incommensurate magnetic ordering of the V sublattice with a propagation vector $\mathbf{q}\ensuremath{\approx}(0,0,0.306)$. This suggests strongly correlated vanadium, which does not contribute significantly to the Fermi surface of ${\text{Sr}}_{2}{\text{VO}}_{3}\text{FeAs}$.