Ferroelectric domain states of a T-BiFeO3 thin film investigated by second harmonic generation microscopy

We investigate a ferroelectric domain state of a multiferroic tetragonal(T)-BiFeO3 thin film by using second harmonic generation (SHG) microscopy. We illuminate the sample with a femtosecond laser with a center wavelength of 800 nm, and monitor the SHG response with full variations of input and output polarizations of light. By scanning the sample with a beam size reduced down to 1 $\mu $m, we could observe clear signatures of nano- and micro-sized domains and their inhomogeneous distributions. Also, we observed a clear signature of temperature-dependent phase transition in the muliferroelectric state which is possibly attributable to the rotation of the polarization axis by 45 degrees