Magnetic properties of Ce–Nd–Fe–Mo alloys and their nitrides

Abstract New quaternary alloys of Ce 1− x Nd x Fe 12− y Mo y with x =0, 0.2, 0.4, 0.6, 0.8, 1 and y =0, 1.5, 2 have been prepared and magnetically hardened by melt spinning. X-ray diffraction indicates that the as-spun materials exhibit the tetragonal ThMn 12 -type structure. Prior to nitriding, the coercivity H ci is less than 0.6 kOe in all alloys and is independent of Nd content, while the magnetization 4 πM 19 (measured in an applied field of 19 kOe) and Curie temperature T c increase with added Nd content x . The effects of nitriding pressure P , time t , and temperature T on magnetic properties have been carefully evaluated on NdFe 10 Mo 2 in order to identify the optimal nitriding parameters. The optimized nitriding profile was subsequently adopted to nitride the remaining samples. After nitrogenation, T c and 4 πM 19 have been substantially enhanced primarily due to the increased Fe–Fe exchange from nitrogen induced lattice dilation. Benefitting from the positive contribution from Nd, H ci has been greatly improved in the Nd containing samples. As a result, Ce 0.2 Nd 0.8 Fe 10 Mo 2 nitride features H ci =2.9 kOe and (BH) max =1.6 MGOe and Ce 0.2 Nd 0.8 Fe 10.5 Mo 1.5 nitride demonstrates H ci =2.5 kOe, (BH) max =1.5 MGOe at room temperature, and T c =337 °C, which are substantial advancements compared to the pure Ce based ThMn 12 -type materials previously reported.