Magnetic Properties of Interstitially Modified Ce–Nd–Fe–Mo–N Magnets Prepared by Spark-Plasma Sintering

Ce-Nd-Fe-Mo nitrides with tetragonal ThMn
₁₂
-type structures are promising compounds for hard magnetic applications. The key to enhance magnetic performance is the insertion of a light element, such as N into the 2b site of the crystal lattice. However, the nitrogenation also changes the thermodynamic stability of Ce-Nd-Fe-Mo whose nitride will disproportionate at elevated temperature. This drawback poses a serious challenge to the sintering of bulk magnets. In this paper, we applied spark-plasma sintering (SPS), a rapid powder consolidation technique, to preparing bulk Ce-Nd-Fe-Mo-N magnets, and developed suitable sintering parameters through thermal analysis, X-ray diffraction, and magnetic property measurement. Without using any binder or additive, we demonstrated a dense magnet that features H
_ci
= 3.34 kOe, remanence B
_r
= 6.55 kG, magnetization 4πM
₁₉
= 9.12 kG, and energy product (BH)max = 4.98 MGOe at room temperature, a performance that shows no degradation compared with the as-nitrided powder. Hence, it is anticipated that an SPS technique is applicable to sintering like metastable or reactive materials, such as (Ce, Nd)-(Fe, Co)-B for their sought-after functional properties.