The enhancement of optic and magnetic properties induced by intrinsic strain in Bi(Mn_0,5Ti_0,5)O₃ modified BiFeO₃ bismuth ferrite

A sol-gel method was employed to synthesize phase-pure (1-x)BiFeO₃-xBi(Mn_0.5Ti_0.5)O₃ (abbreviated as BFO-xBMT, x = 0–0.10) multiferroic ferrites. The investigation focused on the structure, optical, and magnetic properties, and their dependence on composition. X-ray diffraction analysis (XRD) revealed a single phase rhombohedral structure for BiFeO₃ (BFO), with distinct double peaks (104)/(110) and (006)/(202) at diffraction angles 2θ ∼ 32.0° and 39.5°. As the content of Bi(Mn_0.5Ti_0.5)O₃ (BMT) increased, a structural transition from rhombohedral (R3c) to pseudo-cubic (Pm3m) phase was observed. Doping with BMT led to a decrease in particle size. The band gap (E_g) of BFO-xBMT materials exhibited a slight increase from 1.99 eV in BFO to 2.18 eV in the BFO-0.10BMT composition. The introduction of BMT resulted in a significantly enhanced room temperature ferromagnetism in BiFeO₃, with the maximum magnetic moment doubling to around 5.7 emu/g for the BFO-0.04BMT solid solution. This improvement is attributed to the addition of BMT inducing intrinsic strain in the crystal lattice, suppressing the intrinsic helical spin structure of BFO, and thus enhancing its latent magnetic potential. The research demonstrated the substantial influence of BMT perovskite on the structure, optical, and magnetic properties of BFO materials. Overall, the results suggest that the BFO-xBMT multiferroic ferrites with optimal composition hold promise for use in multifunctional devices.