Ultrafast Anisotropic Optical Response and Coherent Acoustic Phonon Generation in Polycrystalline BaTiO3-BiFeO3

By: Brenden Magill, Kyoung-Duck Park, Yuan Zhou, Anuj Chopra, Deepam Maurya, Shashank Priya, Markus Raschke, Alexey Belyanin, Christopher J. Stanton, and Giti Khodaparast

Energy Harvesting and Systems 3, 229 (2016)

We optically study the as-yet little explored multiferroic material, BaTiO3-BiFeO3 (BTO-BFO), that has demonstrated enhanced magnetic properties, a higher DC resistance in comparison to BFO, and improved magnetoelectric coupling. Our studies include: ultrafast time resolved differential reflection, optically induced birefringence, and second-harmonic nano-imaging of the ferroic order. We observe a strong sensitivity to pump/probe polarizations, photo-induced ferroelectric poling on a picosecond timescale, as well as the generation of photo-induced coherent acoustic phonons with a frequency of ~11 GHz. The second-harmonic generation nano-imaging reveals disordered but distinct ferroelectric domain order, percolating even across grain boundaries in the poly-crystalline thin film.