Strong magneto-optical enhancement in highly Ce-substituted iron garnet films prepared by sputtering

Faraday rotation and ellipticity spectra were measured at photon energies hν=0.9–4.0 eV for R3−xCexFe5O12 (R=Y, Gd, Yb) films with substitutions up to x=2.5, expitaxially grown by rf sputtering. The Ce substitution prominently enhances the Faraday effect not only in the IR region at hν=1.4 eV but also in the UV region at hν=3.1 eV. Both transitions have a paramagnetic dispersion relation, which are nearly equal in magnitude but opposite in sign. Optical absorption is also induced by a new transition due to Ce3+ at hν=2.1 eV, which does not enhance Faraday rotation. These electronic transitions may be attributed to charge transfer transition Ce3+(4f)-Fe3+(tet.).