Orbitally driven spin pairing in the three-dimensional nonmagnetic Mott insulator BaVS3: Evidence from single-crystal studies

Static electrical and magnetic properties of single crystal BaVS3 were meas ured over the structural (T-S=240 K), metal insulator (T-MI=69 K), and susp ected orbital ordering (T-X=30 K) transitions. The resistivity is almost is otropic both in the metallic and insulating states. An anomaly in the magne tic anisotropy at Tx signals a phase transition to an ordered low-T state. The results are interpreted in terms of orbital ordering and spin pairing w ithin the lowest crystal-field quasidoublet. The disordered insulator at T- X<T<T-MI is described as a classical liquid of nonmagnetic pairs.