The Aurivillius’ family systems, when doped with magnetic elements at the B-site of the structure, become potential candidates for practical applications as multiferroic systems. A magneto-electric four-layered structure (${\mathrm{Bi}}_5{\mathrm{FeTi}}_3{\mathrm{O}}_{15}$) can be obtained by inserting ${\mathrm{BiFeO}}_3$ into ${\mathrm{Bi}}_4{\mathrm{Ti}}_3{\mathrm{O}}_{12}$, a classical three layers perovskite. The substitution of ${\mathrm{Fe}}^{3+}$ by ${\mathrm{Co}}^{3+}$ in the ${\mathrm{Bi}}_5{\mathrm{FeTi}}_3{\mathrm{O}}_{15}$ compound enhances the ferromagnetic properties with a remnant magnetization at room temperature around 3.9 memu/g. In this work, the ${\mathrm{Bi}}_{4.2}{\mathrm{La}}_{0.8}{\mathrm{Fe}}_{0.5}{\mathrm{Co}}_{0.5}{\mathrm{Ti}}_3{\mathrm{O}}_{15}$ ceramic system was prepared in order to evaluate the lanthanum influence on the physical properties of the ${\mathrm{Co}}^{3+}$ co-doped ${\mathrm{Bi}}_5{\mathrm{FeTi}}_3{\mathrm{O}}_{15}$ compound. A single-phase orthorhombic perovskite structure ($A{2}_{1}am$) has been identified by using X-ray diffraction technique. The Scanning Electronic Microscopy image, collected at room temperature, reveals well-defined plates-like grains in correspondence with the Aurivillius’s structure. Ferroelectric and magnetic hysteresis at room temperature showed the multiferroic character of the studied material with a remnant polarization and remnant magnetization of 0.14 µC/cm2 and 0.44 emu/g, respectively. The obtained value for the remnant magnetization is higher than the previous reported for the ${\mathrm{Bi}}_5{\mathrm{Fe}}_{0.5}{\mathrm{Co}}_{0.5}{\mathrm{Ti}}_3{\mathrm{O}}_{15}$ multiferroic ceramic system, which suggests an interesting material for spintronic applications. The dielectric analysis showed an important effect of the electrical conductivity on the dielectric response. An anomalous behavior has been observed in the temperature dependence of the imaginary component of the dielectric permittivity, which is not observable for the real dielectric permittivity.

ACKNOWLEDGMENTS: The authors would like to thank the Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste-Italy, for financial support of Latin-American Network of Ferroelectric Materials (NET-43, currently NT-02), and CNPq and FAPEMIG Brazilian agencies for financial support.