The $R{\text{VO}}_3$ perovskites undergo orbital ordering and orbital-flipping transitions as well as a spin ordering transition. However, the existing model of orbital ordering fails to explain the thermal conductivity, which remains poor and glassy in the orbitally ordered phase. The phonon thermal conductivity is restored only below a first-order orbital-flipping transition. Orbital ordering induces a specific lattice distortion, which makes uniaxial pressure suitable to distinguish and verify all possible orbital and spin orderings in orthorhombic $R{\text{VO}}_3$. We have made a systematic study of orbital/spin transitions in single-crystal samples of $R{\text{VO}}_3$ $\left(R=\text{Dy},{\text{Y}}_{1-x}{\text{La}}_x\right)$ under uniaxial and hydrostatic pressure. Comparison of the uniaxial and hydrostatic pressure effects on the spin/orbital-flipping transition permits us to identify orbital fluctuations due to the hybridization of $t_2$ and $et$ orbitals in the type-$G$ orbitally ordered phase.

• Received 11 September 2009

DOI:https://doi.org/10.1103/PhysRevB.80.224422