FARADAY EFFECTS IN Rh4+ -AND Ir4+ -SUBSTITUTED MAGNETIC GARNETS

Abstract

Large Faraday rotations are reported tor Rh4+-substituted magnetic garnets in the visible wavelength region, in comparison with those observed in Ir4+ substituted ones. Although rather strong absorptions are observed in the visible region, no absorption peaks corresponding to the Faraday rotation peaks are observed in the absorption spectra. In order to study the origin of the Faraday rotations, Rh4+-and Ir4+-substituted nonmagnetic garnet films are prepared by an LPE method and optical absorption spectra are measured. In addition, the electronic state calculation of (M4+O62-)8- (M=Rh,Ir) octahedral clusters are performed by using the SCF-Unrestricted -SW Xα method. From the observed absorption spectra in nonmagnetic garnets and the electronic state calculations, large Faraday rotations are assigned to the charge transfer transitions of an electron from O 2p to Rh 4d or Ir 5d orbitals, or t1un → t2g* and t2un → t2g* transitions.