Structural and multiferroic properties of (Sm, Mn) co-doped BiFeO<sub>3</sub> materials

Abstract

Pure BiFeO3 (BFO) and (Sm, Mn) co-doped materials were synthesized by the citrate method. Effects of (Sm, Mn) co-doping on the structural, magnetic, electrical and ferroelectric properties of the BFO materials were characterized and investigated by different techniques, such as X-ray diffraction (XRD), Raman scattering spectroscopy, magnetic hysteresis (M-H) loops, electric polarization hysteresis loops, and complex impedance spectra measurements. Analysis results of the XRD measurement show that all samples were crystallized in the rhombohedral structure with R3C space group and crystal lattice parameters of a = 0.5584 nm, c = 1.3874 nm and the average crystal size of LXRD = 60 nm for BFO sample. The crystal lattice parameters a, c and the average crystal size LXRD of (Sm, Mn) co-doped samples were found to decrease with the increasing Sm concentration. The Raman scattering spectral show that the position of peaks characteristic for the Fe-O bonds in the (Sm, Mn) co-doped samples shifts toward lower frequency compared to that of BFO. For the (Sm, Mn) co-doped samples, the position of peaks characteristic for Bi-O covalent bonds shifts toward higher frequencies when the Sm concentration increases, confirming that Sm3+ and Mn2+ ions are substituted into Bi-sites and Fe-sites, respectively. The data from the magnetic hysteresis loop measurements indicate that all samples exhibit weak ferromagnetic behavior. The BFO sample presents weak ferromagnetic properties with a saturation magnetization of Ms = 0.015 emu/g and the remnant magnetization of Mr = 0.007 emu/g. Ferromagnetic properties of the (Sm, Mn) co-doped samples are found enhanced compared to those of BFO. The origin of ferromagnetism of the materials has been considered.