Structural, magnetic and electrical properties of Ho and Ni co-doped BiFeO3 materials

Abstract

Pure BiFeO₃ (BFO) and Bi_1-xHo_xFe_0.97Ni_0.03O₃ (x = 0.00, 0.025, 0.05, 0.075, and 0.10) materials were synthesised by sol-gel method. Effects of (Ho, Ni) co-doping on structural, magnetic and electrical properties of BFO materials were investigated by different techniques as X-ray diffraction (XRD), energy dispersion X-ray (EDX), Raman scattering, magnetic hysteresis (M-H) loops, and complex impedance spectra measurement. Analysis results of XRD measurement shows that all samples crystallize in the rhombohedral structure with R_3C space group. BFO in the rhombohedral structure has crystal lattice parameters a = 5.584 Å, c = 13.867 Å and average crystal size L_XRD = 60 nm. The x = 0.00 sample (BFNO) has a = 5.589 Å, c = 13.875 Å and L_XRD = 60 nm. However, the crystal lattice parameters a, c and average crystal size L_XRD of (Ho, Ni) co-doped samples decrease when concentration of Ho increases. Results of Raman scattering spectra shows that the peaks position characteristic for Fe-O bonds of x = 0.00 sample shifts toward lower frequency compare to that of BFO. For the (Ho, Ni) co-doped samples (BHFNO), the peaks position characteristic for Bi-O convalent bonds shifts toward higher frequency when concentration of Ho increases. Which confirmed that Ho³⁺ and Ni²⁺ ions substituted into Bi-sites and Fe-sites, respectively. From data of magnetic hysteresis loops measurement indicates that all samples present weak ferromagnetic. BFO sample presents weak ferromagnetic properties with saturation magnetization Ms = 0.047 emu/g and remnant magnetization Mr = 0.008 emu/g. Ferromagnetic properties of (Ho, Ni) co-doped samples enhance compare to that of BFO. In this report, we will discuss the origin of ferromagnetism of materials.