Kovaleva, N. N. Boris, A. V. Yordanov, P. Maljuk, A. Brücher, E. Strempfer, J. Konuma, M. Zegkinoglou, I. Bernhard, Christian Stoneham, A. M. Keimer, B. 2007-10-26 We have studied the temperature dependence of spectroscopic ellipsometry spectra of an electrically insulating, nearly stoichiometric YTiO₃ single crystal with ferromagnetic Curie temperature <i>T</i>_<i>C</i>=30 K. The optical response exhibits a weak but noticeable anisotropy. Using a classical dispersion analysis, we identify three low-energy optical bands at 2.0, 2.9, and 3.7 eV. Although the optical conductivity spectra are only weakly temperature dependent below 300 K, we are able to distinguish high- and low-temperature regimes with a distinct crossover point around 100 K. The low-temperature regime in the optical response coincides with the temperature range in which significant deviations from a Curie-Weiss mean-field behavior are observed in the magnetization. Using an analysis based on a simple superexchange model, the spectral weight rearrangement can be attributed to intersite <i>d</i> _i¹<i>d</i> _j¹→<i>d</i> _i² <i>d</i> _j⁰ optical transitions. In particular, Kramers-Kronig consistent changes in optical spectra around 2.9 eV can be associated with the high-spin-state (³<i>T</i>₁) optical transition. This indicates that other mechanisms, such as weakly dipole-allowed <i>p</i>-<i>d</i> transitions and/or exciton-polaron excitations, can contribute significantly to the optical band at 2 eV. The recorded optical spectral weight gain of the 2.9 eV optical band is significantly suppressed and anisotropic, which we associate with complex <i>spin-orbit-lattice</i> phenomena near the ferromagnetic ordering temperature in YTiO₃. application/pdf https://folia.unifr.ch/global/documents/300599 https://folia.unifr.ch/documents/300599/files/bernhard_orf.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1103/PhysRevB.76.155125 info:eu-repo/semantics/openAccess License undefined Physical Review B: Condensend Matter and Materials Physics. - 2007, vol. 76, no. 15, p. 155125 info:eu-repo/classification/udc/57 Optical response of ferromagnetic YTiO₃ studied by spectral ellipsometry http://purl.org/coar/resource_type/c_6501