Strain modulated optical properties in BiFeO3 thin films

Abstract

Spectroscopic ellipsometry was used to investigate the strain-dependent optical properties of BiFeO3 thin films. At room temperature, the compressively strained BiFeO3/LaAlO3 thin films show the largest band gap of about 3.12 eV. It redshifts to 2.75 eV for the tensile strained BiFeO3/NdScO3 thin films. With increasing temperature, observable anomalies in the band gap for all strained thin films near 640K indicate that antiferromagnetic transition temperature is independent of strain and close to its bulk value, which are in good agreement with the first-principles calculations. These results further suggest a complex nature of charge-spin coupling in multiferroic BiFeO3 thin films. (c) 2013 AIP Publishing LLC.