Microstructure and magnetic properties of (Pr,Tb)2(Fe,Nb,Zr)14B/α-Fe nanocomposites

The microstructure and magnetic properties of ${\mathrm{Pr}}_2{\mathrm{Fe}}_{14}\mathrm{B}\mathrm{/\alpha -}\mathrm{Fe}$ nanocomposites with small amount of Tb, Nb, and Zr additions have been investigated. A c-axis texture in the 2:14:1 phase has been observed in ribbons spun at speeds below 14 m/s. Optimal magnetic properties were found in annealed samples spun at 14–17 m/s. With small additions of Nb and Zr, the coercivity significantly increases. Nb substitution leads to a poor loop squareness, which can be significantly improved with Zr addition due to a refinement in microstructure, resulting in a drastic increase in the energy product. Optimum magnetic properties with a room temperature coercivity of 8.2 kOe, and $(\mathrm{BH}{)}_m\text{=20.3\hspace{0.05em}}\mathrm{MGOe}$ have been obtained in ${\mathrm{Pr}}_7{\mathrm{Tb}}_1{\mathrm{Fe}}_{87}{\mathrm{Nb}}_{\text{0.5}}{\mathrm{Zr}}_{\text{0.5}}{\mathrm{B}}_4$ ribbons. Transmission electron microscopy on this sample revealed a much finer and homogeneous microstructure with an average grain size of 20 nm.