Magnetic hardening of CeFe12−xMox and the effect of nitrogenation

We report the magnetic hardening of CeFe12−xMox by melt spinning at surface wheel speeds between 10 m/s and 30 m/s. The synthesis range of CeFe12−xMox has been extended to CeFe11Mo, which uses the least amount of Mo substitution to stabilize the ThMn12-type structure. X-ray diffraction indicates that as-spun samples are multi-phased, typically consisting of a primary ThMn12-type phase with impurity phases of Fe-Mo alloy, Ce2Fe17 and CeFe2. However, nearly pure ThMn12-type phase can be obtained either by directly melt spinning at specific wheel speeds or by annealing the over-quenched ribbons at an optimum temperature. The magnetic moment of CeFe12−xMox is found to be affected not only by the number of Fe atoms but also by weakening of the Fe moment from Mo substitution. Nitriding is effective in enhancing the Curie temperature Tc and saturation magnetization 4πMs. Tc was enhanced by at least 151 °C after nitrogenation for all compositions. The newly identified CeFe11Mo compound exhibits the best magnetic properties in the alloy series, having Tc = 370 °C and 4πMs > 13.0 kG after nitriding and (BH)max = 0.3 MGOe after annealing.