Melt-spun precipitation-hardened Sm2(Co, Cu, Fe, Zr)17 magnets with abnormal temperature dependence of coercivity

Rapidly quenched ${\mathrm{Sm(Co}}_{\mathrm{bal}}{\mathrm{Cu}}_{\mathrm{0.08}}{\mathrm{Fe}}_{\mathrm{0.22}}{\mathrm{Zr}}_{\mathrm{0.02}}{\mathrm{)}}_{\mathrm{8.5}}$ (Cu-/Fe-rich) and ${\mathrm{Sm(Co}}_{\mathrm{bal}}{\mathrm{Cu}}_{\mathrm{0.05}}{\mathrm{Fe}}_{\mathrm{0.10}}{\mathrm{Zr}}_{\mathrm{0.03}}{\mathrm{)}}_{\mathrm{8.5}}$ (Cu-/Fe-poor) ribbons have been prepared by means of the melt-spinning technique. By applying an appropriate annealing procedure a microstructure similar to that of sintered magnets can be obtained. The energy dispersive x-ray microanalysis of the compositional dependence near the cell boundaries suggests a model for the profile of the crystal anisotropy constants responsible for the magnetic hardening. The Cu-/Fe-rich alloy shows a normal temperature dependence of coercivity with a negative temperature coefficient, but the Cu-/Fe-poor ribbons show a positive temperature coefficient in the temperature range from 400–700 K. The different temperature coefficients are discussed in terms of a pinning model.