Superexchange interaction in orbitally fluctuating RVO3

Changes in pressure and magnetic field in the orbital and magnetic ordering temperatures of RVO3 perovskites are reported; they reveal a competition between two magnetic orbitally ordered phases that have opposite preferences for the e-orbital component in the localized T-3(1g) ground state of the V3+ ion. This competition is shown to be biased by the VO6/2 site distortion intrinsic to the orthorhombic structure. A remarkable enhancement of T-N with pressure is found where the competition leads to enhanced orbital critical fluctuations.