Enhanced ferromagnetic properties and high temperature dielectric anomalies in Bi0.9Ca0.05Sm0.05FeO3 prepared by hydrothermal method

Abstract

Enhanced ferromagnetic properties and high temperature dielectric anomalies in the temperature range of 300-873 K in Bi0.9Ca0.05Sm0.05FeO3 (BCSFO) prepared by hydrothermal method are reported. BiFeO3 is seen to crystallize in rhombohedrally distorted perovskite structure without any impurity phase. Substitution of small amount of Ca and Sm (Bi0.9Ca0.05Sm0.05FeO3) leads to increase in the lattice constant values and formation of small amount of secondary phase. Magnetization curve of pure BFO indicates very weak ferromagnetism combined with antiferromagnetic nature of the samples. Whereas, BCSFO sample shows very clear and enhanced ferromagnetic nature. Saturation magnetization and Neel's temperature values are found to be 4.36 emu/g and 664 K, respectively. X-ray photoelectron spectroscopy indicates the creation of oxygen vacancies upon Ca substitution in Bi site. Dielectric anomalies at 420 and 540 K were observed for Bi0.9Ca0.05Sm0.05FeO3 from the temperature variation of dielectric constant and specific heat capacity measurements. Observation of dielectric anomalies in pure BiFeO3 sample reveals that the origin of dielectric peaks is purely from the primary phase. Raman spectroscopy study indicates a clear shift and broadening of A modes (between 100 and 200 cm(-1)) at the dielectric anomaly temperatures supporting the observed dielectric anomalies.