Structural evolution and magnetization enhancement of Bi _1-xTb_xFeO₃

The structural, vibrational, and magnetic properties of well prepared Bi_1-xTb_xFeO₃ (x=0-0.2) powders are investigated by combining the X-ray diffraction, Raman scattering, and magnetometry measurements. It is found that partial substitution of Tb (10-12.5%) in Bi site results in a structural transformation from the rhombohedral R3c symmetry to the orthorhombic Pnma phase, accompanied by a ferroelectric-paraelectric phase transition. The magnetization of Bi_1-xTb_xFeO₃ first gradually increases before reaching maximum at the polar-nonpolar phase boundary and then decreases for x≥0.125 until x=0.20. The enhancement of the remnant magnetization is attributed to the suppression of the space-modulated spin structure in the rhombohedral R3c phase. Meanwhile, the reduction of the remnant magnetization in the orthorhombic Pnma phase is suggested to result from the establishment of well parallel antiferromagnetic ordering.