High quality epitaxial films of the multiferroic BiFeO3 - PbTiO3 have been prepared using pulsed laser deposition. Using an electric field, we will induce a ferroelectrically driven phase transformation - previous experiments on PEARL with bulk materials have shown that this is feasible. This structural transformation will induce a change in the ferromagnetism, which hase been shown to exist in BiFeO3.The ferromagnetic ordering will be probed as a function of composition, substrate - film lattice mismatch and electric field strength. This exiting proposal will provide a physical mechanism for the magnetoelectric effect, and proven device prototype.