Orbitally-Driven Magnetism In Correlated Electron Systems

Over the past decade, we have : (1) developed phenomenological theory for the behavior of "well-ordered" magnetic states of moderately delocalized light rare earth and actinide systems (characteristically obtaining unusual anisotropic magnetism in agreement with experiment) ; (2) developed theory and computational technique to synthesize first principles electronic structure information into that phenomenological theory to make it materially predictive. As discussed below, the resulting theory allows us to predict the triggering of an instability from unusual anisotropic, but well-ordered, magnetism to an unstable state. The unstable state can be either of a valence fluctuation type or of what probably is a heavy fermion type, and the detailed way in which these two types of instability is triggered differs.