Microstructures and High Frequency Properties of ${hbox{Sm}}^{3+}$ Doped ${hbox{Co}}_2{hbox{Z}}$ -Type Hexagonal Ferrites as Anti-EMI Magnetic Bead Materials

摘要

The ${hbox{Sm}}^{3+}$ doped ${hbox{Co}}_2{hbox{Z}}$ -type hexagonal ferrite materials were prepared by conventional ceramic method and characterized by techniques such as X-ray diffractometer and scanning electron microscopy. The influence of a small amount of ${hbox{Sm}}^{3+}$ addition on structures and magnetic properties of the materials was investigated. The results show that ${hbox{Co}}_2{hbox{Z}}$ -type hexaferrite is still in the main phase of the ${hbox{Co}}_2{hbox{Z}}$ ferrite materials doped with ${hbox{Sm}}^{3+}$ . It is observed that Sm-rich phase with granular morphology is dispersed in the main phase. The hysteresis measurement indicates that the specific saturation magnetization of ${hbox{Sm}}^{3+}$ doped sample is bigger than that of the undoped one. The addition of ${hbox{Sm}}^{3+}$ in ${hbox{Co}}_2{hbox{Z}}$ ferrite can decrease the real part $mu^prime$ and the imaginary part $mu^{primeprime}$ of complex permeability, but increase significantly the cutoff frequency. The ${hbox{Sm}}^{3+}$ doped ${hbox{Co}}_2{hbox{Z}}$ ferrites sintered at 1250 $^circ{hbox{C}}$ exhibited excellent high frequency properties such as high cutoff frequency above 1.8 GHz and higher initial permeability up to 5.