Weak ferromagnetism and nanodimensional ferroelectric domain structure stabilized in the polar phase of Bi1−xNdxFeO3 multiferroics via Ti doping

Abstract

Crystal structure, microstructure, local ferroelectric, and magnetic properties of the Bi0.9Nd0.1Fe1−xTixO3 samples have been investigated at room temperature to reveal the effect of Ti4+ doping on the multiferroic behavior of the lanthanide-modified compound representing a polar (space group R3c) antiferromagnetic phase of the Bi1−xLnxFeO3 perovskites. Ti doping results in a gradual suppression of the rhombohedral distortions, however, symmetry of the crystal structure remains the same in the entire concentration range allowing the single-phase perovskites to be obtained (x ≤ 0.08). The doping tends to reduce existing lone-pair cation-driven polar displacements, thus giving rise to a decrease of the ferroelectric polarization in the Bi0.9Nd0.1Fe1−xTixO3 (x→0.08) series. A drastic (from ∼10 μm for x = 0 to ∼1 μm for 0.02 ≤ x ≤ 0.08) decrease of the average grain size induced by the doping is accompanied by the formation of a ferroelectric domain structure with the average domain width of ∼40 nm. Finally, the doping was shown to induce an antiferromagnetic to weak ferromagnetic transformation. The maximum remanent magnetization observed in the Bi0.9Nd0.1Fe1−xTixO3 series at x ∼ 0.05 coincides with the locked magnetization releasing upon the magnetic field-induced suppression of the magnetic cycloid in pure BiFeO3.