Spin and orbital physics in insulating vanadium oxide

The transition metal oxide V₂O ₃ evokes wide ranging research interest due to diverse and complex physical phenomenon it exhibits. The material has a rich phase diagram with four phases that are characterized by remarkably different properties. In recent years, the unique properties and phenomenon observed in the insulating regime of V₂O₃ have received a lot of attention. In addition to the long standing issue of the unusual magnetic ordering in the magnetically ordered insulating phase, recent experimental studies including neutron and resonant x-ray scattering, and x-ray absorption studies have raised new, interesting questions of the complex physics of the disordered and magnetically, ordered insulating phases and the transition between these phases.; In this work we have tried to gain a comprehensive physical understanding of insulating V₂O₃ by developing a microscopic S = 2 bond model that is based on spin and orbital degrees of freedom, and is consistent with the parameters and phenomenology of this system. We have used this model to study insulating V₂O₃ in different temperature and parameter regimes, and thereby tried to elucidate the role played by spin and orbital physics in governing the interesting behavior observed in this system.; We find that using the S = 2 bond model with spin and orbital degrees of freedom, we can satisfactorily explain not only the anomalous magnetic ordering, but also all the other properties of the disordered and magnetically ordered insulating phases observed by experimental studies. The model also shows a phase transition between these phases which is completely consistent with the phenomenology of the magnetic transition in insulating V₂O₃. In addition, the S = 2 model predicts changes in the phase transition phenomenology for the AFI transition in the presence of magnetic field, and the possibility of an additional phase transition at lower temperatures.; In this work, we have explored a broad range of intriguing phenomenon associated with the V₂O ₃ insulator. In addition to resolving the long standing issue of the anomalous magnetic ordering in insulating V₂ O₃, we have been able to answer the questions raised by recent experimental studies. We have also been able to make experimentally verifiable predictions that can help us establish the validity of our approach.