Aluminium-doped BiFeO₃ as a potential multiferroic material

Epitaxial films of BiAl_xFe_1-xO₃ (xBAFO) are a candidate for alternate multiferroic materials. xBAFO films are grown on SrTiO₃ (001) (STO) and SrRuO₃ buffered STO substrates using pulsed laser deposition technique. The X-ray diffraction patterns show that phase-pure xBAFO can be synthesized for x ≤ 0.35 without any secondary phases. xBAFO retains  rhombohedral structure as BiAlO₃ and BiFeO₃ are isotypic. The ferroelectric properties of xBAFO are explored by analyzing P-V hysteresis loops. The shape of the loops changes from being square to increasingly slanted with higher Al doping. The domain growth mode, morphology, size, dimension and nucleation have a crucial role on the switching behavior. To analyze the switching behavior, domain images have been studied using piezo-response force microscopy. With increasing concentration of Al, the films exhibit higher resistance enabling the application of higher voltage. We demonstrate a reduction of piezoelectric coercive voltage is achieved by increasing substitution of Fe by Al on BFO. Since the spin ordering of Fe atoms is modified by Al, enhancement in magnetic properties is also expected. These results suggest that xBAFO is a potential multiferroic material to realize BFO-based next generation non-volatile memory devices.