Ferromagnetism in the Multiferroic Bi_5FeTi_3O_(15) Ceramics Arising from the Magnetic Coupling

Multiferroic Bi_5Fe_(1-x)Co_xTi_3O_(15)(x = 0～0.6) ceramics were prepared using solid state reaction method. XRD pattern confirmed the single phase in all prepared samples and Raman scattering technique was also used to study the crystal structure.The remanent magnetization(2M_r) is increased to a high value of 2.3 mA·m~2/kg with the cobalt content of 0.5.This value is two orders of magnitude greater than that of non-doped one.The promising ferromagnetism is attributed to the coupling arising from local Fe-O-Co clusters as well as the influence of net magnetic moment of Fe-O-Co clusters on the magnetic behavior.The remanent polarization(2P_r) is increased by a small amount of cobalt of 0.1,then decreased with further doing of cobalt up to 0.4,after that,2P_r is increased again up to a cobalt content of 0.6.The dependence of 2P_r on cobalt content is attributed to the joint effect of lattice distortion, charge compensation and the change of covalent bonding condition.