First principles study of magnetic properties of Zn-Sn substituted M-type Sr-hexaferrite

Site occupancy and magnetic properties of Zn-Sn substituted M-type Sr-hexaferrite SrFe$_{12-x}$(Zn$_{0.5}$Sn$_{0.5}$)$_x$O$_{19}$ with $x=1$ were studied using density functional theory and generalized gradient approximation (GGA). Using the GGA+U method the description of strongly correlated $3d$ electrons of Fe was improved. Our results show that Zn and Sn atoms prefer to occupy $4f_1$ and $4f_2$ sites respectively. Favorable Zn-Sn substituted configurations show an increase in saturation of magnetization (M$_s$), and a decrease in magnetic anisotropy energy (MAE), over the pure M-type Sr-hexaferrite ($x=0$). Experimental observations agree with the decrease of MAE and the increase of M$_s$ for Zn-Sn substituted Sr-hexaferrite.