Coexistence of strong ferromagnetism and polar switching at room temperature in Fe3O4-BiFeO3 nanocomposite thin films

10% Fe3O4-90% BiFeO3 nanocomposite thin films of 180 nm thickness were grown by pulsed laser deposition on SrTiO3 (011) single crystals. A 3-4 nm nanolamella structure of Fe3O4 and BiFeO3 was formed. While BiFeO3 has the expected epitaxial relationship with the substrate, Fe3O4 grew epitaxially and highly strained (7%). Compared to pure Fe3O4 films of similar thickness, the nanolamella structure of Fe3O4 gives rise to a greatly enhanced saturation magnetization of 900 emu/cc, and, after field cooling, an enhanced coercivity of 450 Oe. Piezoresponse force microscopy measurements show similar polar switching properties between the nanocomposite and pure BiFeO3 films. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3500826]