Magnetization behavior and magnetic viscosity in nanocomposite Pr₉Fe₇₄Co₁₂B₅Sn_x (x=0, 0.5) ribbons

Nanocomposite Pr₉Fe₇₄Co₁₂B₅ and Pr₉Fe₇₄Co₁₂BSn_0.5 ribbons were directly prepared by melt-spinning. Measurements of reversible and irreversible magnetization and magnetic viscosity were performed on the ribbons. It is found that the demagnetization curves of the both samples show a single hard phase behavior at room temperature, while a two-phase behavior at low temperature. The sample with Sn addition, because of its more homogeneous microstructure, shows a more obvious two-phase behavior than the Sn free one at low temperature. Furthermore, the increase of the volume fraction and grain sizes of the soft phase, in the Sn-doped ribbons, increases the portions of reversible magnetization and decreases the nucleation field H_n. The investigation of the magnetic viscosity shows that the activation volume is related to the grain sizes of the soft phase.