Epitaxially grown la-modified BiFeO3 magnetoferroelectric thin films

Abstract

Effects of the La modification on the structure and magnetoferroelectric properties of BiFeO3 (BFO)-based films were examined. On SrTiO3 (001) planes, all the BFO-based films (for x between 0 and 0.15 in Bi1-xLaxFeO3 with the film thickness of 300 nm) were grown epitaxially along [001] direction of tetragonal symmetry. However, the La modification gradually changes the film structure from a monoclinically tilted state to a nontilted tetragonal-like state. Both extended x-ray absorption fine structure and x-ray absorption near edge structure spectra revealed the presence of a strong in-plane compressive stress. Room-temperature magnetization-field curves indicated that the saturation magnetization of these BFO-based epitaxial films increased with the degree of La modification. La-modified BFO film capacitors fabricated on SrRuO3-buffered SrTiO3 (001) substrates showed fatigue-free ferroelectric switching characteristics up to 4x10(10) read/write cycles at a frequency of 1 MHz. (c) 2005 American Institute of Physics.