GIANT MAGNETOOPTIC ROTATIONS - THE ROLE OF ORBITAL POLARIZATION AND EXPLICIT CORRELATION-EFFECTS

In an effort to understand the giant magnetooptic Kerr rotations of a class of cerium and uranium compounds, an ab initio itinerant-electron calculation for these compounds has been performed over the full frequency range studied experimentally. The band structure used is obtained from a self-consistent spin-polarized full-potential linearized muffin-tin orbital (SPLMTO) calculation with a true interstitial. Similar calculations were first performed for iron and nickel and good agreement was obtained with experiment. Unlike Ni and Fe, it was found that for the class of compounds that display giant Kerr rotations, such a conventional calculation provides magnetooptic behavior very different from experiment. This poor agreement was anticipated due to the presence of their large orbitally driven magnetism totally unlike the magnetism of Ni and Fe, and because of the possible importance of explicit correlation effects (not captured by an exchange-correlation potential) on approaching heavy fermion behavior. The poor agreement of their calculated moments to experiment bore this out and as a next step, explicit orbital polarization was incorporated into our band calculation. This brings about a much better agreement for their ordered magnetic moments but still fails to provide adequate agreement for their magnetooptic behavior; and furthermore, in distinction to a calculation including explict correlation effects, it does not provide agreement with the experimental ordered moment for the incipient heavy fermion CeTe system. Thus it appears that the inclusion of explict correlation effects (i.e., energy differences associated with different configurations) is important for understanding giant magnetooptic effects.