The origin of the coercivity in Co-Zr system alloys

The phases and magnetic properties of Co-Zr melt-spun ribbons were studied to investigate the origin of the hard magnetic phase in Co-Zr system alloys. The Co-Zr melt-spun ribbons with coercivities of 1.5-2.7 kOe consisted of a metastable Co₅Zr phase together with fcc-Co and Co₂₃Zr₆ phases. Annealing at relatively high temperatures (700-800°C resulted in the formation of an equilibrium Co₁₁Zr₂ phase). However, the annealed ribbons with the Co₁₁Zr₂ phase showed a lower coercivity than those without the Co₁₁Zr₂ phase. The hard magnetic phase of the Co-Zr system alloys was believed to be the metastable Co₅Zr phase.