Preparation and investigation of Ce:YIG thin films with a high magneto-optical figure of merit

Cerium-substituted yttrium iron garnet (Ce-x Y3-x Fe5O12 or Ce : YIG) thin films with a high Ce content are very hard to achieve because of the solubility limit of Ce in the yttrium iron garnet (YIG) structure. In this work a Ce : YIG target with nominal formula of CeY2Fe5O12 was fabricated by the conventional ceramic method. Phase formation and crystal structure of the samples were investigated by the x-ray diffraction (XRD) method and the results showed that the minimum temperature to get a single phase CeY2Fe5O12 is 1400 degrees C. CeY2Fe5O12 thin film was deposited on a GGG (4 4 4) single crystal substrate, using the pulsed laser deposition method and its microstructure and magneto-optical (MO) properties were studied. Trying different conditions, a preferred (4 4 4) oriented CeY2Fe5O12 thin film was fabricated under an optimum condition. The results showed that a crystalline CeY2Fe5O12/GGG thin film can be obtained by annealing of the as-deposited film at 600 degrees C. XRD measurements on the annealed thin film showed that the mean grain size was 38 nm, using Scherrer's formula. Scanning electron microscopy image of the annealed thin film showed that the mean grain size was 35 nm, which is in good agreement with XRD measurements. Atomic force microscopy (AFM) image of the annealed sample showed that the thin film had a smooth surface. Faraday rotation provided by the thin film at wavelength lambda = 635 nm was measured to be 2.4 degrees mu m(-1) in a magnetic field of 600mT. Transmission spectrum of the thin film was recorded in the visible and near-infrared regions, from 400 to 1000 nm, and it showed good transparency, more than 78%, in the near-infrared region. These measurements resulted in an MO figure of merit of 0.146, which is one of the highest values reported up to now. It is expected that CeY2Fe5O12 thin films could be used as new Faraday rotator materials, applicable in optical isolators and circulators.