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

Abstract

The Sm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> doped Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 Sm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> addition on structures and magnetic properties of the materials was investigated. The results show that Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Z-type hexaferrite is still in the main phase of the Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Z ferrite materials doped with Sm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> . 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 Sm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> doped sample is bigger than that of the undoped one. The addition of Sm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> in Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Z ferrite can decrease the real part μ' and the imaginary part μ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">''</sup> of complex permeability, but increase significantly the cutoff frequency. The Sm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> doped Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Z ferrites sintered at 1250°C exhibited excellent high frequency properties such as high cutoff frequency above 1.8 GHz and higher initial permeability up to 5.