The phase transition and superior multiferroic properties of (Mn, Co) co-doped BiFeO3/CoFe2O4 double-layer films

(Mn, Co) co-doped BiFeO3/CoFe2O4 (BFMCO/CFO) double-layer films were prepared on fluorine doped tin oxide (FTO)/glass substrates by the chemical solution deposition method. The effect of (Mn, Co) co-doping on crystal structure, ferroelectric and magnetic properties of BFO/CFO double-layer films was investigated. Mn and Co co-doping on the BiFeO3 layer induced the tendency of phase transformation from rhombohedral to tetragonal. Well saturated polarization hysteresis loops were observed in BFMCO/CFO films, meanwhile a giant remanent polarization of the double-layer films (P-r similar to 123 mu C/cm(2), after compensation) is obtained. Furthermore, an enhanced ferromagnetic behavior of M-s similar to 113 emu/cm(3), M-r similar to 67 emu/cm(3) and H-c similar to 1200 Oe is observed in BFMCO/CFO films. The reduction of Fe2+ and the existence of high valence iron ions with co-doping Mn and Co were confirmed by XPS. Therefore, the difference of magnetic moment of TM2+/3+ and Fe3+ may play a more important role in the suppression of the spiral spin modulation. As a result, the introduction of (Mn, Co) and CoFe2O4 layer is an effective way to enhance the multiferroic behavior of the films. (C) 2015 Elsevier B.V. All rights reserved.