Dynamic magnetoelectric effect in bismuth-layer structured Aurivillius ceramics

Multiferroic materials have been developed and studied for decades due to their potential applications in microelectronics and spintronics, such as multi-state digital memories, energy storage, and ultra-fast electric field-controlled magnetic sensors. Among these materials, magnetoelectric multiferroics exhibit a magnetoelectric (ME) interaction allowing for the manipulation of polarization by a magnetic field and magnetization by an electric field through internal strain and/or charge. However, strain-mediated ME effect is time-consuming and inefficient at high frequencies (∼ GHz). To address this issue and pave the way toward high frequency applications of ME multiferroics, we have systematically designed and characterized layered Bi5FeTi3O15-type Aurivillius ceramics for a strong dynamic ME coupling in the GHz band. By introducing cobalt and niobium ions into Bi4.3Gd0.7FeTi3O15, a phase evolution from a four-layered structure to a mixed structure consisting of four- and three-layered phases was revealed. The Co/Nb co-doping was found to enhance the magnetization at room temperature while preserving ferroelectricity. The understanding of the substitution-enhanced dynamic ME coupling at satellite and radar communication frequencies is expected to broaden the range of applications for ME multiferroics.