Effects of BaTiO_3 and SrTiO_3 as the buffer layers of epitaxial BiFeO_3 thin films

BiFeO_3 (BFO) thin films with BaTiO_3 (BTO) or SrTiO_3 (STO) as buffer layer were epitaxially grown on SrRuO_3-covered SrTiO_3 substrates. X-ray diffraction measurements show that the BTO buffer causes tensile strain in the BFO films, whereas the STO buffer causes compressive strain. Different ferroelectric domain structures caused by these two strain statuses are revealed by piezoelectric force microscopy. Electrical and magnetical measurements show that the tensile-strained BFO/BTO samples have reduced leakage current and large ferroelectric polarization and magnetization, compared with compressively strained BFO/STO. These results demonstrate that the electrical and magnetical properties of BFO thin films can be artificially modified by using a buffer layer.