Effects of the Bi~(3+) substitution on the structural, vibrational, and magnetic properties of bismuth layer-structured ferroelectrics

摘要

Bismuth layer-structured ferroelectric Bi_3R_2Ti_3FeO_(15) (R = Bi, Nd, and Gd) ceramics were synthesized by conventional solid-state reaction. All the samples showed an orthorhombic structure with A2_1am space group. Bi_3Nd_2Ti_3FeO_(15) and Bi_3Gd_2Ti_3FeO_(15) presented a reduction in the orthorhombicity when compared to Bi_5Ti_3FeO_(15). The magnetic susceptibility of all samples followed the Curie-Weiss law, with negative values of the Curie-Weiss temperature, demonstrating that the magnetic interactions are antiferromagnetic in nature. The magnetization curves suggested a weak canted antiferromag-netic behavior for temperatures below 25 K, followed by a linear behavior in the curves at high temperatures. Mossbauer spectroscopy measurements revealed an increase of the quadrupole splitting values as the temperature decreases, indicating that the samples present local distortions, favoring the existence of weak ferromagnetic phase via the antisymmetric Dzya-loshinskii-Moriya interaction.