Accurate analysis of the magneto-optical permittivity tensor of Y3Fe5O12

The permittivity tensor elements epsilon(0) (diagonal) and epsilon(1) (off-diagonal) elements of Y3Fe5O12 (YIG) were analyzed as a function of frequency to gain insight into the cause of electric dipole transitions that produce Faraday or Kerr effects in a magnetized state. A continuous set of spectral measurements of the reflection Kerr ellipticity and rotation were carried out with high density ceramic specimens utilizing a photoelastic modulated ellipsometer across the visible band from 2.0 to 4.0 eV. The spectra of epsilon(0) and epsilon(1) deduced from the measurements were then fitted to select individual transitions. From the line shapes, it was determined that the epsilon(1) transitions responsible for the Kerr effects are of the orbitally split ground state (paramagnetic) type, despite the fact that the pure ground state of the Fe3+ ion has no orbital magnetic moment. From the results of the analysis, quantitative estimates from a molecular-orbital model are offered for the magnitude of spin-orbit splitting of the Fe3+ S-6 ground states hybridized covalently with Fe3+ T-4(1g) excited states at neighboring sites of the opposing magnetic sublattice. (C) 2003 American Institute of Physics.