Achieving multiferroic properties in bismuth titanate ceramics via a tri-doping engineering mechanism with Co, Sm, and La at room temperature

The discovery of advanced single-phase multiferroic materials at room temperature is expected to significantly impact the development of a wide range of electronic devices for next-generation applications. Based on this goal, the Co ions were selected as acceptors in the Ti4+ site of the Bi-3.25(Sm0.50La0.50)(0.75)Ti3O12 (BSLT) host lattice. The obtained systems show excellent ferroelectric, magnetic, and magnetodielectric properties. According to the structural analysis, no secondary phase could be observed, and all the prepared samples exhibited layered perovskite structures belonging to the n = 3 Aurivillius family. The morphological study shows that the average grain size decreases with increasing Co content. The ferroelectric and magnetic studies show that the residual polarization and magnetization exhibit opposite variations depending on the doping. The XPS results confirm that the Co is present in a mixed valence state, namely Co2+ and Co3+. This suggests that the ferromagnetism at room temperature could be due to a double exchange interaction between the neighboring Co2+ and Co3+ ions and the oxygen ions. The study of the dielectric constant shows that the real and imaginary dielectric constants have the same trend and increase directly with the magnetic field increase. This indicates that the predominant mechanism of the MD effect is not an extrinsic Maxwell-Wagner mechanism but rather an intrinsic mechanism involving spin realignment of the Co2+-Co3+ dipoles.