Tuning the ferromagnetic and ferroelectric properties of BiFeO3 multiferroic nanofibers by Co/Ni spinel ferrites

Abstract

BiFeO 3 –(Co/Ni)Fe 2 O 4 (BFO–(C/N)FO) multiferroic nanofibers were synthesized using a self-assembly coaxial electrospinning technique. The structure, exchange bias effect, ferromagnetic, and ferroelectric properties were investigated using various physical and chemical characterization approaches. The coexistence of a spinel–perovskite mixed structure was verified in (BFO–(C/N)FO) nanofibers by X-ray diffraction and X-ray photoelectron spectroscopy. Raman spectra revealed a distorted crystal structure or more complex phase configurations with overlapping features. Compared to the pure BFO nanofibers, the magnetic properties showed a significantly increase after recombination. BFO–NFO nanofibers exhibited higher exchange coupling through switching field distribution analysis. The ferroelectric properties of the composite nanofibers were considerably changed compared to pure BFO nanofibers, which can be attributed to the presence of impurities (Bi 2 Fe 4 O 9 ) and the asymmetrical spin in spinel ferrites. The BFO–CFO nanofibers exhibited larger leakage current and coercive electric field than the other two types of nanofibers. Hence, coupling of the structural distortion and crystal phases are important approaches in altering the ferroelectric and ferromagnetic properties. These results suggest that the BFO–(C/N)FO nanofibers have potential applications in multifunctional nanodevices. • Pure BFO, CFO, NFO, BFO–NFO, and BFO–CFO nanofibers were synthesized using the self-assembly coaxial electrospinning method, and the influence of Co/Ni spinel ferrites equivalent co-composite on the ferromagnetic and ferroelectric properties of BFO nanofibers was investigated systematically. The four phases such as BiFeO 3 , CoFe 2 O 4 (NiFe 2 O 4 ), Bi 2 Fe 4 O 9 and a little Bi 2 O 3 (BFO-CFO)are existed in BFO-C/NFO nanofibersand the phases percentage ratio were calculated. • Meanwhile,the Mr and Hc values for the BFO–NFO and BFO–CFO nanofibers were 12.5 emu/g and 864.7 Oe and 15.8 emu/g and 1326.9 Oe, respectively, which were higher than that of the pure BFO nanofibers. • Besides, the reason for polarization unsaturation of BFO–C/NFO nanofibers was related to the addition of certain amount of impurities (Bi2Fe4O9). • The results imply that the recombination between BFO and CFO/NFO results in significant high leakage current density.