THE ROLE OF ORBITAL POLARIZATION AND CORRELATION-EFFECTS IN THE MAGNETOOPTIC BEHAVIOR OF CESB AND CETE

CeSb and CeTe show giant magneto-optic Kerr rotations and also have extremely unusual magnetic ordering properties. CeSb shows peculiar and extraordinarily anisotropic antiferromagnetic behavior; while CeTe shows an ordered moment and T(N) only 15% that of CeSb, indicative of incipient heavy-fermion behavior. This has been understood in an absolute theory of orbitally driven correlated f-electron magnetism. We seek to understand the giant magneto-optic properties including the role, if any, of explicit correlation effects not captured by an exchange-correlation potential. To this end we have performed full potential linearized muffin-tin orbital polarized band calculations for the optical conductivity tensor, first only spin polarized (orbital polarization only via spin-orbit coupling) and second with explicit orbital polarization. As expected, for CeSb and CeTe the spin-polarized calculation gave the diagonal, ordinary optical, conductivity in good agreement with experiment; but the off-diagonal, magneto-optic, behavior was in poor agreement; and the ordered moment was much different from experiment. For the spin-and-orbitally polarized calculation, the ordered moment agreed reasonably well with experiment for CeSb but very poorly for CeTe. However, the magneto-optic behavior remained distinctly different from experiment for both materials. Thus as anticipated, explicit correlation effects associated with differing discrete f-configuration energies appear to be a central aspect of giant magneto-optic behavior.