Molecular-Orbital Analysis of Magneto-Optical Bi-O-Fe Hybrid Excited States

摘要

Molecular-orbital estimates of the excited-state spin-orbit coupling multipletsplitting are presented to support the theory that enhanced magneto-optical effects in Y(3-x)Bi(x) Fe5O12 originate from covalent interactions between Bi(3+) and Fe(3+) ions. A self-consistent approximation is applied to a two-level bonding-antibonding hybrid formed from the excited (4)P term of Fe(3+) and the excited (3)P of Bi(3+). For term energy values chosen from spectroscopic data, overlap integrals s <0.05 are sufficient to account for bonding-state depressions that match those reported for the tetrahedral and octahedral site-enhanced transitions at 2.6 and 3.15 eV. The hybrid eigenfunctions of the upper states can contain more than 30% of the Bi(3+) (3)P orbital term. Multiplet splittings that are enhanced by the large Bi(3+) spin-orbit coupling constant (lambda approx. 2 eV) are found to be on the order of 0.5 eV with a full complement of Bi surrounding Fe in the garnet lattice, in agreement with estimates based on experiment. p2.