Investigation into the role of Co doping in the microstructure and magnetic characteristics of nanocrystalline Nd-Ce-La-Fe-B alloys

Abstract

In this study, [Nd0.5(Ce0.5La0.5)0.5]17Fe78-xCoxB6 (x = 0 ∼ 1.5 at. %) ribbons are prepared via a direct melt-spun (wheel speed of 28 m/s). The impacts of Co doping on the crystal structure, Curie temperature Tc, magnetic parameters (Br, Hci and (BH)max) of [Nd0.5(Ce0.5La0.5)0.5]17Fe78-xCoxB6 alloys are systematically assessed. X-ray diffraction patterns and Rietveld refinement data demonstrate that the exclusive presence of a pure hard magnetic 2:14:1 phase without any secondary phases across all samples. Compared with Co-free sample (x = 0), the Br, Hci and (BH)max of Co-doped with x = 1 are increased by 15.0 %, 4.6 % and 42.9 %, respectively. The coercivity mechanism in the [Nd0.5(Ce0.5La0.5)0.5]17Fe78-xCoxB6 alloys arises from the integration of reversed domain nucleation and robust pinning of domain walls. The magnetic domain structure and quantitative analysis based on the microstructure and demagnetization behavior are conducted to investigate the exchange coupling interactions among the 2:14:1 grains. This exploration reveals that the enhanced magnetic properties stem from the refinement of the 2:14:1 phase's grains, leading to more uniform and smaller interaction domains.