부산대학교 도서관

Improvement of hard magnetic property for melt spun CeCo5 ribbons by doping proper Fe and C is demonstrated. Low magnetic properties, remanence ( $B_{r}$ ) of 4.2 kG, coercivity ( ${}_{i}H{}_{c}$ ) of 1.6 kOe, and energy product [ $(\textit {BH})_{\max }$ ] of 1.8 MGOe, are found for binary CeCo5 ribbons due to extremely large size of grains, even prepared at a high wheel speed of 40 m/s. ${}_{i}H{}_{c}$ is largely enhanced to 12.8 kOe by doping C and 15.0 kOe by co-doping Fe and C, and therefore, $(\textit {BH})_{\max }$ is increased to 3.5 and 5.1 MGOe, respectively. The coercivity achieved in this work is superior to those reported ever before, and $(\textit {BH})_{\max }$ is also larger than the theoretical value of 4.7 MGOe for isotropic CeCo5 alloy. X-ray diffraction (XRD) and thermomagnetic analysis (TMA) results reveal Fe and C enter into the 1:5 phase to modify the lattice constant and increase $T_{C}$ , and the increased $c/a$ ratio of the 1:5 phase may improve $H_{a}$ and contribute to enhancing the coercivity. Microstructure analysis indicates the grain size is effectively refined by doping C and co-doping Fe and C. Fine microstructure for C-containing ribbons contributes to attaining a high coercivity of 12.8–15.0 kOe. Besides, Fe-doping may increase the magnetization of the 1:5 phase, and therefore improve the remanence and $(\textit {BH})_{\max }$ . The results of this work suggest that the magnetic properties of CeCo5 ribbons could be improved by modification of 1:5 crystal and microstructure refinement due to proper Fe and C-codoping.