The influence of Tb substitution on the magnetic properties of nanocomposite Pr/sub 2/Fe/sub 14/B//spl alpha/-Fe magnets

Tb-doped (Pr,Tb)/sub 2/Fe/sub 14/Be//spl alpha/-Fe nanocomposite ribbons have been synthesized by melt-spinning Pr/sub 8-x/Tb/sub x/Fe/sub 86/B/sub 6/ alloys at low speeds. The effects of Tb substitution and rapid annealing on the magnetic properties of the composites were investigated. With a small addition of Tb, the Curie temperature of hard phase increases slightly, the saturation magnetization decreases but the coercivity increases due to a higher anisotropy field and a refinement of grain size, leading to an enhancement in the energy product. Transmission electron microscopy revealed a finer and more homogeneous (Pr,Tb)/sub 2/Fe/sub 14/B//spl alpha/-Fe microstructure with an average grain size in the range from 20 to 40 nm. The best results are obtained with a room temperature coercivity of 6.6 kOe, M/sub r/=118 emu/g, and (BH)/sub m/=15.2 MGOe in Pr/sub 7/Tb/sub 1/Fe/sub 86/B/sub 6/ sample annealed at 800/spl deg/C for 1 minute.