Nanosized Zn_0.6Cu_0.4Gd_xFe_2－xO₄ (x＝0～0.10) ferrites doped with Gd and polypyrrole/Zn_0.6Cu_0.4Gd_0.04Fe_1.96O₄ nanocomposites were prepared by a sol-gel method and an in situ polymerization method, respectively. The structures, morphology, conductive and magnetic properties of ferrite powders and nanocomposites were characterized by means of modern analytical techniques. The results showed that the saturation magnetization of the ferrites doped with Gd increased with increase of Gd content. The conductive and magnetic properties of composites depended on the polypyrrole content. As the polypyrrole content increased from w＝50% to w＝80%, the conductivity increased from 0.0139 to 0.0423 S/cm, while the saturation magnetization decreased from 18.37 to 14.35 emu/g. The pure PPy with thickness of 2 mm showed a minimum reflection loss of －19.68 dB at 16 GHz and an available bandwidth of 6.2 GHz in the 7～18 GHz range. The minimum reflection loss value and the available bandwidth of ZCCFS_0.04O had only －16.6 dB and 5.16 GHz. PPy/Zn_0.6Cu_0.4Gd_xFe_2－xO₄ composites with w＝20% Zn_0.6Cu_0.4Gd_xFe_2－xO₄ had the minimum reflection loss of －20.90 dB and available bandwidth was broadened to 11.30 GHz. The results show that the PPy/ZCGFO composites could be used as advancing microwave absorption and shielding materials due to their favorable microwave absorption properties.

Key words: ferrite, PPy, in situ polymerization, nanocomposite, electrical/magnetic property