Enhancing the performance of rare-earth free permanent magnets: A computational study of nitrogen and oxygen defects in CoPt, CoFePt2, and CoNiPt2 alloys

Abstract

This work presents a computational investigation utilizing density functional theory and Monte Carlo simulations to study the influence of nitrogen and oxygen defects on the structural and magnetic properties of CoPt, CoFePt2, and CoNiPt2 alloys. The goal of this study was to explore their potential applications as alternatives to rare-earth permanent magnets. Our findings have revealed that the incorporation of nitrogen and oxygen defects significantly influence the magnetic properties of these alloys. The incorporation of defects yields negative formation energies, thereby confirming the structural stability of the defective structures. In addition, phonon dispersion calculations further confirmed the dynamical stability of the defective structures with lower formation energies. Notably, the Curie temperature (Tc) of CoFePt2 increased upon the addition of nitrogen, while the magnetocrystalline anisotropy energy (EMCA) of CoNiPt2 was enhanced by the presence of oxygen. In contrast, no improvement in the saturation magnetization was observed. These results provide valuable insights toward the development of rare-earth-free permanent magnets with tailored magnetic properties.