Origin of high room temperature ferromagnetic moment of nanocrystalline multiferroic BiFeO3

Abstract

Single phase nanocrystalline BiFeO3 of average crystallite size ∼25 nm with very high magnetization at room temperature is synthesized by an autocombustion method. Magnetic measurements above room temperature show deviation between field cooled and zero field cooled magnetization below 645 K, the Néel temperature (TN) of the bulk material, indicating intrinsic nature of ferromagnetism. However, observation of a broad magnetic transition above TN of BiFeO3 and extended up to 800 K suggests the presence of Fe3O4 as a possible magnetic impurity phase. Evidence for the presence of Fe3O4 is obtained from detailed analysis of the powder x-ray diffraction pattern.