The structural and multiferroic properties of (Bi _1-xLa _x)(Fe _0.95Co _0.05)O ₃ ceramics

La and Co co-doped BiFeO ₃ ((Bi _1-xLa _x)(Fe _0.95Co _0.05)O ₃ (x=0, 0.10, 0.20, 0.30)) ceramics were prepared by tartaric acid modified sol-gel method. The X-ray diffraction patterns indicate a transition from rhombohedral structure to tetragonal structure at x=0.20, which has been confirmed by the Raman measurements. The band gap increases with increasing x to 0.20, and then decreases with further increasing x to 0.30. The structural transition has significant effects on the multiferroic properties. The remnant magnetization and saturate ferromagnetic magnetization decrease abruptly with increasing x to 0.10, and then gradually increase with further increasing x up to 0.30. The coercivity is significantly reduced with increasing La doping concentration. The ferroelectricity has been improved by La doping, and the polarization increases with increasing x to 0.10, then decreases with further increasing x up to 0.30. The simultaneous coexistence of soft ferromagnetism and ferroelectricity at room temperature in tetragonal Bi _0.70La _0.30Fe _0.95Co _0.05O ₃ indicates the potential multiferroic applications.