Abstract
We report a thorough study of Y0.7La0.3VO3 single crystals by measuring magnetic properties, specific heat, thermal conductivity, Raman scattering, x-ray and neutron diffraction with the motivation of revealing the lattice response to the spin-orbital entanglement in RVO3. Upon cooling from room temperature, the orbitally disordered paramagnetic state changes around T∗∼220 K to a spin-orbital entangled state which is then followed by a transition at TN = 116 K to C-type orbital-ordered (OO) and G-type antiferromagnetic ordered (AF) ground state. In the temperature interval TN<T<T∗, the VO6/2 octahedra have two comparable in-plane V-O bonds which are longer than the out-of-plane V-O1 bond. This octahedral site distortion supports the spin-orbital entanglement of partially filled and degenerate yz/zx orbitals. However, this distortion is incompatible with the steric octahedral site distortion intrinsic to orthorhombic perovskites. Their competition induces a second-order transition from the spin-orbital entangled state to a C-OO/G-AF ground state where the long-range OO suppresses the spin-orbital entanglement. Our analysis suggests that the spin-orbital entangled state and G-OO are comparable in energy and compete with each other. Rare-earth site disorder favors the spin-orbital entanglement rather than a cooperative Jahn-Teller distortion. The results also indicate for LaVO3 a C-OO/G-AF state in Tt ≤ T ≤TN and an orbital flipping transition at Tt.
