Y1−xLaxVO3: Effects of doping on orbital ordering

Abstract

The effects of isovalent doping on orbital ordering in the perovskite ${\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{VO}}_{3}$ were investigated using neutron diffraction and the pair distribution function analysis. ${\mathrm{YVO}}_{3}$ is a prototype for orbital ordering, exhibiting two consecutive transitions to G-type and C-type ordering with decreasing temperature. Evidence for local orbital ordering above the transition temperature of ${T}_{OO}\ensuremath{\sim}200$ K is presented, obtained from the temperature dependence of the oxygen-oxygen octahedral correlations. This suggests that locally, G-type orbital ordering is present above the ${T}_{OO}$ temperature but it is short range. With doping, it is expected that orbital ordering disappears altogether. By 30% of doping, as in ${\mathrm{Y}}_{0.7}{\mathrm{La}}_{0.3}{\mathrm{VO}}_{3}$, even though no orbital ordering is expected, we find that locally, C-type orbital correlations are most likely present below the magnetic transition temperature ${T}_{N}$, allowing for a direct paramagnetic to orbitally ordered/antiferromagnetic transition in this composition.