Coexistence of electric polarization and magnetic ordering in acceptor doped potassium sodium niobate (KNN) ceramics

Lead-free single-phase multiferroic K0.5Na0.5Nb1−xFexO3 (x = 0.02, 0.03, 0.04, 0.05) ceramics have been synthesized by solid-state reaction method to explore the simultaneous existence of ferroelectric and magnetic order. X-ray diffraction analysis of the samples confirms no phase separation and impurity phase formation with the increase of Fe2O3 concentration. The morphology, lattice fringes and SAED pattern of KNN ceramics studied from HR-TEM studies. The structural transition from orthorhombic—tetragonal (TO−T) and tetragonal—cubic (TC) have been studied for all compositions through temperature dependent dielectric measurements. Existence of Fe in multi-oxidation states such as Fe2+, Fe3+ and oxygen vacancy have been studied through X-ray photoelectron spectroscopy (XPS) analysis. Lowering of band gap noticed for all the Fe doped KNN samples from UV/Vis absorbance studies. Presence of defect dipoles such as and oxygen vacancies leads to pinning of domains give rise to asymmetric P-E and S-E response. Further, the observed intrinsic magnetic ordering in K0.5Na0.5Nb1−xFexO3 could be explained through various exchange interactions.