Nanocrystalline multiferroic BiFeO3thin films made by room temperature sputtering and thermal annealing, and formation of an iron oxide-induced exchange bias

Abstract

Multiferroic nanocrystalline BiFeO3films have been successfully made by room temperature sputtering and thermal annealing in oxygen at 500 °C. Nanocrystalline Bi was seen before annealing as well as β-Bi2O3and the iron oxide phases, magnetite, maghemite, and FeO. Superparamagnetism was observed that can be attributed to magnetite and maghemite nanoparticles. The thermally annealed film contained BiFeO3nanoparticles and magnetite, maghemite, and hematite as well as unidentified BiFexOyphases. Superparamagnetism was also seen after annealing and the magnetic properties are predominately due to magnetite and maghemite nanoparticles rather than from multiferroic BiFeO3. The saturation magnetic m..