Core-Shell Rare Earth Magnet Coercivity

The patent applies local quality by creating a core-shell structure where the core region contains high concentration of heavy rare earth elements (Dy, Tb, or Ho) to provide strong pinning effect and high coercivity, while the shell region contains light rare earth elements (Nd, Pr) to maintain saturation magnetization. This spatial differentiation of element distribution allows the magnet to achieve high coercivity with minimal overall heavy rare earth content, directly resolving the contradiction between improving coercivity and reducing heavy rare earth consumption.

The patent employs parameter changes by precisely controlling the concentration gradients of rare earth elements within the core-shell structure. The core contains heavy rare earth elements at concentrations optimized for high-temperature coercivity, while the shell contains light rare earth elements at concentrations optimized for saturation magnetization. This parameter optimization allows the magnet to maintain reliability at high temperatures while minimizing the overall amount of expensive heavy rare earth elements required, thereby reducing manufacturing cost.

The core-shell structure implements local quality by concentrating heavy rare earth elements in the core region where they provide strong pinning effects to enhance coercivity, while the shell region is composed of light rare earth elements that contribute to high saturation magnetization. This spatial separation ensures that the heavy rare earth elements do not uniformly distribute throughout the grain, preventing the overall reduction of residual magnetic flux density while still achieving high coercivity through localized pinning at the core-shell interface.