Effect of rare-earth ion doping on the multiferroic properties of BiFeO3thin films grown epitaxially on SrTiO3(1 0 0)

High-quality epitaxial Bi 1− x RE x FeO 3 (RE=La, Nd, Gd; x = 0, 0.05, 0.15) thin films were prepared on SrTiO 3 (1 0 0) substrates using pulsed laser deposition. X-ray diffraction and RBS-channelling spectroscopy showed that the films are single-phase perovskite, free of additional phases and textured with preferential orientation along the [1 0 0] direction. The dependences of magnetization on temperature and field showed that the films exhibit weak ferromagnetic properties. Among the studied rare-earth doping ions, Bi 3+ substitution by Gd 3+ most considerably enhanced the ferromagnetic properties. Substitution by La 3+ smoothened out the surface morphology, which is important for different potential applications. Both undoped and doped films showed clear ferroelectric response in piezoresponse force microscopy, thus confirming their multiferroic nature. The doping was found to promote a preferential ferroelectric poling of the domains.