The effects of isovalent doping on orbital ordering in the perovskite Y1−xLaxVO3 was investigated using neutron diffraction and the pair distribution function analysis. YVO3 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 TOO ∼ 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 TOO temperature but it is short-range. With doping, it is expected that orbital ordering disappears altogether. By 30 % of doping as in Y0.7La0.3VO3, even though no orbital ordering is expected, we find that locally, C-type orbital correlations are most likely present below the magnetic transition temperature, TN , allowing for a direct paramagnetic to orbitally ordered/antiferromagnetic transition in this composition.

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The dynamics of the first-order phase transitions involving a large displacement of atoms, for example, a liquid-solid transition, is generally dominated by the nucleation of the ordered phase and the growth of the nuclei, where the interfacial energy between the two phases plays an important role. On the other hand, electronic phase transitions seldom exhibit such a nucleation-growth behavior, probably because two-phase coexistence is not dominated by only the interfacial energy in such phase transitions. In the present paper, we report that the dynamics of a phase transition associated with an ordering of d orbitals in a vanadate exhibits a clear nucleation-growth behavior and that the interfacial energy between the orbital-ordered and -disordered phases dominated by the orbital-spin coupling can be experimentally obtained.

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