Observation of exchange bias properties in Lu substituted BiFeO3

Bi_1-xLu_xFeO₃, x = 0.00, 0.03, 0.05 and 0.07 compounds were synthesized using the solid-state reaction method. Room temperature structural analysis was carried out for the prepared compounds through Rietveld refinement. The studies showed that the compounds were stabilized in a rhombohedral R3c structure at room temperature. UV–visible spectroscopy measurements revealed a slight widening in the optical band gap, from 2.03 eV to 2.08 eV, with the increase in x. The magnetic measurements indicated that remanent magnetization and coercive fields increased with the increase in the Lu substitution. Interestingly, the substituted compounds exhibited exchange bias properties under zero field cooled conditions. Polarization measurements indicated better ferroelectric polarization hysteresis loops observed in the compounds with higher Lu substitution. Impedance measurements demonstrated an improved insulating behaviour with Lu substitution. The grain and grain boundary resistances were extracted using a two-parallel RC circuit model. Additionally, the materials exhibited a negative temperature coefficient of resistance, as was evidenced by the ac conductivity measurements in all the prepared compounds.