Structure Evolution and Multiferroic Properties in Cobalt Doped Bi(4)NdTi(3)Fe(1-x)Co(x)O(15)-Bi(3)NdTi(2)Fe(1-x)Co(x)O(12-δ) Intergrowth Aurivillius Compounds

Here, we report the structure evolution, magnetic and ferroelectric properties in Co-doped 4- and 3-layered intergrowth Aurivillius compounds Bi(4)NdTi(3)Fe(1-x)Co(x)O(15)-Bi(3)NdTi(2)Fe(1-x)Co(x)O(12-δ). The compounds suffer a structure evolution from the parent 4-layered phase (Bi(4)NdTi(3)FeO(15)) to 3-layered phase (Bi(3)NdTi(2)CoO(12-δ)) with increasing cobalt doping level from 0 to 1. Meanwhile the remanent magnetization and polarization show opposite variation tendencies against the doping level, and the sample with x = 0.3 has the largest remanent magnetization and the smallest polarization. It is believed that the Co concentration dependent magnetic properties are related to the population of the Fe(3+) -O-Co(3+) bonds, while the suppressed ferroelectric polarization is due to the enhanced leakage current caused by the increasing Co concentration. Furthermore, the samples (x = 0.1–0.7) with ferromagnetism show magnetoelectric coupling effects at room temperature. The results indicate that it is an effective method to create new multiferroic materials through modifying natural superlattices.