Improved room-temperature multiferroicity in Co-doped Aurivillius Sr_0.5Bi_5.5Fe_1.5Ti_3.5O₁₈ ceramics

Multiferroic Sr_0.5Bi_5.5Fe_1.5−xCo_xTi_3.5O₁₈ (0 ≤ x ≤ 0.5, SBFCT-x) ceramics with layered perovskite structure were successfully prepared by the sol–gel auto-combustion method. The coexistence of ferroelectricity and ferromagnetism was observed at room temperature (RT) for all Co-doped samples. Co substitution can not only remarkably improve ferroelectricity but also enhance the ferromagnetism obviously. In particular, the SBFCT-0.4 sample shows the highest remnant magnetization (2M_r) ~ 1.82 emu/g and the largest remnant polarization (2P_r) ~ 24.4 μC/cm². Furthermore, dielectric anomalies (x = 0.2–0.5) have been found, which can be ascribed to the long-range migration of oxygen vacancies. The effects of Co doping on ferroelectric, magnetic, and dielectric properties were discussed. The SBFCT-0.4 sample was also found to exhibit the magnetoelectric (ME) effect detectable under a low response magnetic field at RT. And the obvious magnetocapacitance (MC) performance was also observed at and above RT (373 K), which is important to potential applications in sensor technology and memory devices.