Structure and magnetic properties of RCo7−xZrx (R=Pr or Er, x=0–0.8)

Alloys of composition ${\mathrm{RCo}}_{\text{7−x}}{\mathrm{Zr}}_x\mathrm{ (}\mathrm{R=Pr}$ or Er and $\text{x=0−0.8)}$ were synthesized and characterized in the temperature range of 10–1273 K in fields up to 5 T. As with the ${\mathrm{SmCo}}_{\text{7−x}}{\mathrm{Zr}}_x$ system studied earlier in our laboratory, the effects of Zr doping on the stability of the ${\mathrm{TbCu}}_{\mathrm{7}}$ phase and the increase in the anisotropy field $H_A$ are also observed in the systems of ${\mathrm{PrCo}}_{\text{7−x}}{\mathrm{Zr}}_x$ and ${\mathrm{ErCo}}_{\text{7−x}}{\mathrm{Zr}}_x.$ Nearly single phase ${\mathrm{TbCu}}_{\mathrm{7}}$ materials were formed in as-cast alloys when $\text{x=0.1–0.2.}$ In the case of $\mathrm{R=Pr},$ $H_A$ changes from almost planar for $\text{x=0}$ to uniaxial with $H_a\text{∼100\hspace{0.05em}}\mathrm{kOe}$ for $\text{x⩾0.2}$ at room temperature (RT). In the case of $\mathrm{R}=\mathrm{Er}{\mathrm{, H}}_A$ for the $\text{x=0.1}$ composition is almost two times larger than that of the Zr-free alloys, which shows strong uniaxial anisotropy at both RT and 10 K. Spin reorientation behavior (when $\mathrm{R=Pr})$ and $\mathrm{R}\mathrm{–M}$ antiparallel coupling (when $\mathrm{R=Er})$ were also observed.