Phase evolution, magnetic study and evidence of spin-two phonon coupling in Ca modified Bi0.80La0.20FeO3 ceramics

Abstract The present studies are focused on the effect of divalent Ca2+ ion on the structural, magnetic, and optical properties of Bi0.80La0.20FeO3 (BLFO) ceramic samples, synthesized via conventional solid-state reaction route. The addition of Ca2+ ion into BLFO substituting Bi, creates distortion in the structure and leads a phase transition from rhombohedral (R3c) to orthorhombic (Pbnm) crystal symmetry, confirmed by Rietveld analysis and further supported by Raman spectroscopy, attributed to a decrease in tilt angle for anti-phase rotation of BO6 octahedra. Weak ferromagnetic ordering was observed for all Bi0.80-xCaxLa0.20FeO3 samples with Ca at.% of 0.03 (BCLFO3), 0.06 (BCLFO6) and 0.12 (BCLFO12), associated to changes in Fe–O–Fe angle. The remnant magnetization has been found to increase from 1.2×10−3 emu/g for BLFO to 9.1x10−3 emu/g for BCLFO12. Similar trends were found in the deconvoluted ferromagnetic contribution with Ca2+ ion doping. Moreover, Arrott plot analysis suggests a second order meta-magnetic transition for all samples. Room temperature dielectric properties were improved with Ca2+ ion substitutions. The optical band gap significantly reduced from 2.10 eV for BLFO to 1.93 eV for BCLFO12, indicating the distortion induced by the Ca2+ ion.