Magnetic properties of Pr–Fe–B melt-spun ribbons with high coerecivity

• The melt-spun ribbons with high coercivity are obtained without heat treatment.
• Co substituted for Fe can reduce portion of amorphous phases.
• Co substituted for Fe can prevent the formation of metastable phase.
• The crystalline grain size increases with increasing Co content.
• α-Fe can precipitate more easily when the crystalline grain size is small.

The hard magnetic materials Pr13.5Fe80.6−xCoxGa0.4B5.5 (x=0, 2, 4, 8 and 15) have been prepared by melt-spinning technique. The melt-spun ribbons with a high coercivity iHc of 23 kOe are achieved without the heat treatments. It is found that Co substitution for Fe can reduce the portion of the amorphous phases and prevent the formation of the metastable phase in the ribbons. The crystalline grain size of the ribbons increases with increase of Co content. The Curie temperature of the magnet increases linearly with Co content x from 568 K for x=2 to 700 K for x=15. The formation of α-Fe is observed using in-situ measurement of the magnetic properties during the heat treatment, indicating that α-Fe phase can precipitate more easily from the ribbons when the crystalline grain size is smaller.