| Summary: | The dielectric function and the bandgap of BiFe<sub>0.5</sub>Cr<sub>0.5</sub>O<sub>3</sub> thin films were determined from spectroscopic ellipsometry and compared with that of the parent compounds BiFeO<sub>3</sub> and BiCrO<sub>3</sub>. The bandgap value of BiFe<sub>0.5</sub>Cr<sub>0.5</sub>O<sub>3</sub> is lower than that of BiFeO<sub>3</sub> and BiCrO<sub>3</sub>, due to an optical transition at ~2.27 eV attributed to a charge transfer excitation between the Cr and Fe ions. This optical transition enables new phonon modes which have been investigated using Raman spectroscopy by employing multi-wavelengths excitation. The appearance of a new Raman mode at ~670 cm<sup>−1</sup> with a strong intensity dependence on the excitation line and its higher order scattering activation was found for both BiFe<sub>0.5</sub>Cr<sub>0.5</sub>O<sub>3</sub> thin films and BiFe<sub>x</sub>Cr<sub>1−x</sub>O<sub>3</sub> polycrystalline bulk samples. Furthermore, Raman spectroscopy was also used to investigate temperature induced structural phase transitions in BiFe<sub>0.3</sub>Cr<sub>0.7</sub>O<sub>3</sub>.
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