Record‐High Performance 2:17‐type SmCo Magnets via Fe‐Driven HRE Segregation

Abstract

ABSTRACT Development of high‐performance SmCo magnets, simultaneously possessing high magnetic energy product ( BH ) max and low remanence temperature coefficient | α |, is critical for applications of wide‐temperature precision instruments. Conventional heavy rare‐earth (HRE) substitution improves temperature stability via antiferromagnetic coupling but inevitably sacrifices ( BH ) max , resulting in a persistent trade‐off between ( BH ) max and | α |. Herein, we propose a Fe‐HRE synergistic compositional‐design strategy that integrates Fe enrichment and HRE segregation to break this bottleneck. First‐principles calculations reveal that increasing Fe concentration provides a thermodynamic driving force for HREs segregation from the 1:5H cell boundary into the 2:17R matrix. Furthermore, molecular field simulations quantitatively demonstrate that HRE enrichment in the 2:17R phase enhances its temperature compensation effect and effectively overcomes this trade‐off. Guided by these insights, a series of Sm 0.4 Gd 0.6 (Co bal Fe x Cu 0.08 Zr 0.025 ) 7.2 ( x = 0.20–0.24) magnets are prepared. Magnetic and microstructural characterizations confirm that moderate Fe enrichment ( x = 0.22) not only improves ( BH ) max but also facilitates Gd segregation into 2:17R phase without microstructural degradations. These synergistic effects yield a record‐high ( BH ) max of 18.8 MGOe and α 20°C–300°C = −0.012%/°C. This work establishes a unified design framework integrating magnetic moment engineering with thermodynamic element distribution regulation, paving a viable path for high‐temperature‐stable SmCo magnets for aerospace precision instruments.