Lead-Free Aurivillius Phase Bi 2 LaNb 1.5 Mn 0.5 O 9 : Structure, Ferroelectric, Magnetic, and Magnetodielectric Effects.

Aurivillius phase Bi 2 LaNb 1.5 Mn 0.5 O 9 , derived from ferroelectric PbBi 2 Nb 2 O 9 by simultaneous substitution of the A -site and B -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 Bi 2 LaNb 1.5 Mn 0.5 O 9 adopts an A 2 1 am orthorhombic crystal structure. Rietveld refinement analysis, supported by Raman spectroscopy, indicates that the Bi 3+ ions occupy the bismuth oxide blocks, La 3+ ions occupy the perovskite A -site, and Nb 5+ /Mn 3+ ions occupy the perovskite B -site. Ferroelectric ordering takes place at 535 K, which coexists with local ferromagnetic order below 65 K. The cation disorder on the B -site results in relaxor-ferroelectric behavior, and the short-range ferromagnetic order can be attributed to Mn 3+ /Mn 4+ 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.