Effects of La/Ho co-substitution on structure and multiferroic characteristics of BiFeO3 ceramics.

The effects of La/Ho co-substitution on multiferroic characteristics were investigated for BiFeO₃ ceramics together with structure evolution. The symmetry in Bi_1−x(La_0.65Ho_0.35)_xFeO₃ ceramics changed from R3c to Pna2₁ and finally Pbnm with increasing x. Ferroelectricity was significantly improved with La/Ho co-substitution, and P_r reached the maximum of 30.9 μC/cm² at 160 kV/cm at x = 0.16, where the R3c/Pna2₁ morphotropic phase boundary was determined. The weak ferromagnetism was released as the symmetry changed from R3c to Pna2₁, and subsequently the saturated M–H loop could be determined gradually with increasing x, and M_r increased continuously. The electric field-controlled magnetism could be characterized by the significant magnetism variation due to the electric field-induced transition of Pna2₁/R3c, which occurred during the poling process, and this transition became reversible by the help of annealing after poling. Compared with the situation of Bi_1−xNd_xFeO₃ (the ion radius is the same as the effective one of La_0.65Ho_0.35), the present co-substituted BiFeO₃ ceramics exhibited superior electric field-induced transition of Pna2₁/R3c with a maximum change rate of 47.03% in remanent magnetization under an electric field, which enhanced the magnetoelectric effect. [ABSTRACT FROM AUTHOR]