Novel approaches for genuine single-phase room temperature magnetoelectric multiferroics

This chapter reviews approaches currently under investigation for the fabrication of single-phase magnetoelectric multiferroics, from bulk ceramics to those in thin-film form. It presents an approach of inserting magnetic ions into the Aurivillius phase, layer-structured ferroelectric materials, whereby thin films of average composition Bi₆Ti_2.8Fe_1.52Mn_0.68O18 (B6TFMO) demonstrate room temperature ferroelectricity, ferromagnetism, and magnetoelectric coupling. The chapter also discusses the importance of careful microstructural analysis of the materials and the application of a statistical model to determine a confidence level that the observed effects are from genuine single-phase magnetoelectric multiferroics. It reviews how careful phase analysis and statistical treatment of the data confirmed that the B6TFMO phase is a single-phase multiferroic to a confidence level of 99.5%. Finally, it summarizes how direct evidence of magnetoelectric coupling in the B6TFMO thin films was obtained. This review demonstrates that with materials development and design, the development of room temperature multiferroic materials can be achieved.