Conduction mechanisms and enhanced multiferroic properties of Sr doped Bi_(0.85-x)Pr_(0.15)Sr_xFe_(0.97)Mn_(0.03)O_3 thin films

摘要

Pure BiFeO_3 (BFO) and Bi_(0.85-x)Pr_(0.15)Sr_xFe_(0.97)Mn_(0.03)O_3 (BPS_XFMO, x = 0.02-0.05) thin films were deposited on fluorine-doped SnO_2 (FTO/glass) substrates by a sol-gel method. The systematic studies of crystalline structure, surface morphologies, leakage conduction mechanisms, ferroelectric and magnetic properties of pure BiFeO_3 and Bi_(0.85-x)Pr_(0.15)Sr_xFe_(0.97)Mn_(0.03)O_3 thin films were investigated. X-ray diffraction patterns, Riet-veld analysis and Raman scattering spectra reveal that the (Pr, Sr and Mn) co-doped BiFeO_3 thin films give rise to a trigonal (R3m: R) structure transition with respect to the original rhombohedral structure of pure BiFeO_3 film. Fowler-Nordheim tunneling conduction mechanism dominates the leakage current of all the films in the relatively high electric field. The significantly enhanced ferroelectric properties of the Bi_(0.85-x)Pr_(0.15)Sr_xFe_(0.97)Mn_(0.03)O_3 thin films were observed in comparison with pure BiFeO_3 film. In addition, the BPS_2FMO film shows the enhanced ferro-magnetism with the saturation magnetization (M_s ～ 1.97 emu cm~(-3)), which is almost three times larger than that of pure BFO film (M_s ～ 0.67 emu cm~(-3)), as a result of the small grain size effect and the collapse of space modulated spin structure by the structure transition.