Electronic excitations and optical properties of YbFe2O4 thin films

Abstract We present the structural, optical properties, and electronic excitation spectra of the YbFe 2 O 4 thin film deposited on (0001) sapphire substrates. The optical spectra of a YbFe 2 O 4 thin film show several electronic transitions, dominated by Fe d to d on-site electronic transitions as well as O 2 p to Fe 3 d , Yb 6 s , and Yb 5 d charge-transfer electronic transitions. The direct energy band gap of YbFe 2 O 4 has been found to be 1.40 ± 0.01 eV at 300 K. Moreover, the electronic transitions centered at 1.75 eV and 2.41 eV exhibit strong temperature dependence with a discontinuity at ∼190 ± 10 K, indicating evidence for a structural instability in the system. The optical spectra of YbFe 2 O 4 have been analyzed and also compared with that of isostructural YFe 2 O 4 and LuFe 2 O 4 .