Critical Limitations in the Fabrication of Biferroic BiFeO3-CoFe2O4 Columnar Nanocomposites Due to Bismuth Loss

The influence of the temperature during self-assembled growth of BiFeO3-CoFe2O4 columnar nanocomposites on (001) and (111) oriented SrTiO3 substrates has been investigated aiming to control pillar size and lateral ordering. The dramatic influence of the growth temperature on the nanoobject morphology is found to be basically due to the strong monotonic reduction in the bismuth content as the deposition temperature increases. There is a very narrow (tens of degrees) optimal window of substrate temperature, in which BiFeO3 could permit a small deficit of Bi without decomposition. The enhanced ferromagnetic response of samples deposited at higher temperature signals formation of secondary ferromagnetic phases caused by BiFeO3 decomposition. Therefore, the deposition temperature is not a suitable free parameter to control the nanoobjects topology in BiFeO3 nanocomposites.