Lead-Free Aurivillius Phase BiLaNbMnO: Structure, Ferroelectric, Magnetic, and Magnetodielectric Effects.

Aurivillius phase BiLaNbMnO, derived from ferroelectric PbBiNbO by simultaneous substitution of the -site and -site cations, was synthesized using a molten-salt method. Here, we discuss the structure-property relationships in detail. X-ray and neutron diffraction show that BiLaNbMnO adopts an 2 orthorhombic crystal structure. Rietveld refinement analysis, supported by Raman spectroscopy, indicates that the Bi ions occupy the bismuth oxide blocks, La ions occupy the perovskite -site, and Nb/Mn ions occupy the perovskite -site. Ferroelectric ordering takes place at 535 K, which coexists with local ferromagnetic order below 65 K. The cation disorder on the -site results in relaxor-ferroelectric behavior, and the short-range ferromagnetic order can be attributed to Mn/Mn double-exchange. Magnetodielectric coupling measured at 5 K and 100 kHz in a field of 5 T suggests the existence of intrinsic spin-lattice coupling with a magnetodielectric coefficient of 0.20%. These findings will provide significant impetus for further research into potential devices based on the magnetodielectric effect in Aurivillius materials.