Effect of Co-Dy Doping on Temperature Stability and Magnetic Properties of Nd-Fe-B Alloy: First-Principles and Characterization Analysis.

Abstract

This research centers on the effect of Co-Dy codoping on temperature stability and magnetic properties of Nd-Fe-B alloy for novel rare-earth magnetic material development. Employing X-ray diffraction (XRD), electron probe X-ray microanalyzer-energy dispersive X-ray spectroscopy (EPMA-EDS), magnetic force microscope (MFM), and magnetic tests, the remanence varies complexly with Co-Dy content, decreasing at low doping due to atomic bond disruption and increasing at high doping via exchange enhancement. Coercivity rises at low Co-Dy doping by multiple mechanisms and drops at high doping due to hard magnetic phase change, with 8.6 wt % Co-Dy doping showing high-temperature stability of remanence and coercivity. The soft magnetic phase's composition, distribution, and Co-Dy content-related changes in its impact on magnetic properties were clarified. Through a combination of experimental and density functional theory (DFT) approaches, the material properties under varying Co-Dy doping levels were systematically investigated. The research involved constructing first-principles calculation models of NdFeBDy with varying Co-Dy content ratios. First-principles calculations identified Co/Dy-preferred Fe sites and doping energy by analyzing state density and magnetic moment changes induced by dual-element doping. Co-Dy codoping synergistically modifies the electronic and magnetic structures, which directly govern the magnetic performance through altered exchange interactions and crystal field effects. Multiple Nd₂Fe¹⁴B samples with diverse Co-Dy content ratios were prepared experimentally. This study offers theoretical and experimental grounds for understanding Co-Dy codoping mechanisms and advancing rare-earth magnetic material performance optimization.