Local polarization switching in Ba–Ni co-doped BiFeO3 thin films with low rhombohedral-symmetry distortion

Abstract

Low rhombohedral-symmetry distortion of (Ba, Ni) co-doped BiFeO3 multiferroic thin films has been achieved on Pt/TiO2/SiO2/Si substrates using RF magnetron sputtering. X-ray diffraction and Rietveld fitting show that the Bi0.75Ba0.25Fe0.975Ni0.025O3 films have an R3c low rhombohedral-symmetry distortion of hexagonal perovskite close to a pseudocubic-type structure and that their crystallographic volume decreases as the sputtering pO2 increases. Ferroelectric characterization and piezoresponse force microscopy demonstrate that the thin films possess ferroelectric domain structure by polarization switching. In addition, the ferroelectric character is connected to FeO6 octahedral distortion because of the incorporation of Ba2+ and Ni2+ in the A and B sites, respectively, changing the stereochemical activity of co-doped BiFeO3 films. Our findings indicate that there is a direct relationship between the sputtering pO2 and the rate of nucleation and growth; as the pO2 is increased, the deposition rate is lower. The maximum magnetic saturation in these thin films was 40 emu/cm3.