Self-modulated growth of a super-large-period multiferroic BiFeCoTiO33 thin-film

The epitaxial growth of super-large-period Aurivillius thin films has been explored in order to study their period-modulated multiferroic property. BiFeCoTiO33 thin films with a pseudo-period of ten have been grown on SrTiO3 single crystal substrates using pulsed laser deposition. The films are found to be coherently strained to the substrates and atomically smooth. The X-ray diffraction indicates an average layer period of 10. While the high resolution scanning transmission electron microscopy reveals a self-modulated nanostructure in which the period changes as the thickness increases. The modulation to the period is tentatively explained by the volatile bismuth stacking difference between hetero-epitaxial growth and homo-epitaxial growth. Nonetheless, the self-modulated large period films exhibit intrinsic ferromagnetic and ferroelectric properties at room temperature.