Conduction mechanisms and enhanced multiferroic properties of 2-2 type Bi0.89Sm0.11FeO3–NiFe2O4 composition thin films

Pure BiFeO3 (BFO), BiFeO3–NiFe2O4 (BFO–NFO) and Sm-doped Bi0.89Sm0.11FeO3–NiFe2O4 (BSFO–NFO) thin films were prepared on FTO/glass (SnO2:F) substrates via a sol–gel method. The effects of NFO layer and Sm-doping on the crystalline structure, leakage current, ferroelectric and ferromagnetic properties of all the thin films were investigated. Rietveld refinement of X-ray diffraction data indicated that BFO phase in BFO–NFO and BSFO–NFO films is trigonal with different space group of R3c:H and R3m:R. The leakage current of BFO film shows Ohmic emission at the entire electric field, whereas the dominant mechanism is changed to Fowler–Nordheim tunneling emission at the high electric field in the BFO–NFO and BSFO–NFO films. The improved ferroelectric and ferromagnetic properties have been observed in the BSFO–NFO film, e.g., large remanent polarization is 66.18 μC/cm2 and large saturation magnetization is 31.86 emu/cm3.