SOURCES OF ANISOTROPY IN RARE-EARTH AND ACTINIDE EXCHANGE INTERACTIONS

Over a period of time we have been developing techniques to evaluate the fundamental interactions for correlated f-electron systems, such as band-f hybridization and band-f coulomb exchange, on the basis of absolute first principle calculations. In this work, we apply the same technique to evaluate the evolution of f-electron behavior from heavy rare earths to light rare earths to actinides. We will discuss how the degree of localization of the f-electrons affects their hybridization and coulomb exchange interaction with the non-f band electrons, and how this influences the two-ion exchange interaction and magnetic ordering. Our calculations are for XSb where X = Ce, Nd, Tb, Er, Yb, U and for CeTe and UTe. The treatment that we present provides a generalization of RKKY theory as it was developed for electronic systems by T. Kasuya and by K. Yosida to the situation where the itinerant component has unquenched orbital angular momentum. The results we so obtain will be compared to results obtained from spin-and-orbitally polarized band theory.