Optical and magneto-optical properties of Co-doped CeO2−δ films in the 0.5 to 4 eV range

Abstract

Magnetically doped Ce1−xCoxO2−δ (nominal x = 0.05 and 0.10) films were systematically studied by spectroscopic ellipsometry and magneto-optical spectroscopy. The samples were prepared by pulsed laser deposition on MgO(100) substrates and grew as textured polycrystalline films with thickness between 200 and 750 nm. They exhibited room temperature ferromagnetism and an out-of-plane easy axis attributed to magnetoelastic effects from the in-plane compressive strain. The dispersion of dielectric function of Ce1−xCoxO2−δ films was parametrized by the sum of Tauc-Lorentz and damped Lorentz oscillators and adjusted numerically. Deduced optical band gaps were similar to those of pure CeO2, but the Co doping increased the optical absorption. The magneto-optical spectroscopy was carried out in both Faraday and Kerr configurations in the photon energy range from 0.5 to 4 eV, showing a strong dependence of the magneto-optical effect on the Co content near the optical band edge.