Direct observation of orbital ordering in V2O3 by X-ray resonant scattering technique

Among the materials exhibiting metal-insulator transition, vanadium sesquio xide V2O3 and its Cr-alloys have received most attention from the theoretic al and experimental point of view. It is now widely agreed that the unusual magnetic properties can be explained by taking both orbital and spin degre es of freedom into account. Whereas many experiments give direct informatio n on the magnetic structure, only indirect evidence suggests the existence of orbital order in cases like V2O3, where it is not accompanied by coopera tive Jahn-Teller distortion. We have demonstrated the existence of orbital ordering in V2O3 by means of X-ray resonant scattering at the vanadium K-ed ge using tunable synchrotron radiation. The observed orbital structure conf irms the interplay between orbital and magnetic order, and provides an illu stration of a new experimental method to extract information on the electro nic orbital occupancy in solids. (C) 2000 Elsevier Science B.V. All rights reserved.