Site preference for Co2+ and Ti4+ in Co-Ti substituted barium ferrite

Co²⁺ and Ti⁴⁺ substituted M-type barium ferrite, BaFe_12-2xCo_xTi_xO₁₉, with x from 0 to 0.9 has been prepared using a modified ceramic method and investigated by electron microscopy, vibrating sample magnetometry and Mossbauer spectroscopy. Results show that Co²⁺ and Ti⁴⁺ cations prefer to occupy the 4f_VI and 2b crystallographic sites, with 4f_IV and 2a sites are only slightly involved as well for x>0.6. These site preferences will significantly weaken the uniaxial anisotropy of this material which is attributed to the contribution of iron ions at the 2b and 4f_VI sites. As a consequence, the coercive force of BaFe_12-2xCo_xTi_xO₁₉ drastically decreases and the magnetization remains almost a constant as x increases