High temperature magnetic properties of nanocrystalline PrCo_5 and YCo_5 alloys obtained by mechanical milling

摘要

Enhanced hard magnetic properties were obtained in nanostructured PrCo_5 and YCo_5 intermetallic compounds processed by mechanical milling for 240 min, and subsequent annealing in high vacuum at 1103 K for 1.0 and 2.5 min, respectively, followed by quenching in water. X-ray diffraction data demonstrate that the annealing has produced an average grain size < D > below 20 nm for both compounds, as a consequence magnetic measurements at room temperature showed a coercivity (H_C) higher than 0.79 MA/m, and enhanced remanence (σ_r/σ_(max) > 0.5). High temperature magnetic measurements showed a temperature dependence of H_C and remanent magnetization σ_r for both compounds, where the temperature coefficient of coercivity for PrCo_5 is bigger than for YCo_5. Such behavior is consistent with the intrinsic temperature variation of magnetocrystalline anisotropy for PrCo_5 and YCo_5 intermetallic compounds.