Composition design and coercivity mechanism of 1∶12-type SmFe permanent magnets

Rare earth permanent magnet materials are widely applied in critical fields such as aerospace，energy technology，and transportation，serving as critical materials in modern technology. The 1∶12-type（ThMn12）SmFe permanent magnet material exhibits magnetic properties comparable to Nd2Fe14B and possesses a higher Curie temperature. It exhibits the highest theoretical magnetic energy product among permanent magnets. Moreover，it consists of abundant elements，showing significant potential for application. However，this material faces challenges in thermal stability，leading to low coercivity，thus hindering its potential. This paper first analyzed the reasons for the poor thermal stability of the 1∶12 phase，concluding the influence of elements occupying different crystallographic sites on phase stability and intrinsic magnetic properties. Subsequently，we analyzed the key factors affecting the coercivity，elucidating the inherent relationship between preparation processes and coercivity. Finally，we proposed strategies for achieving high magnetic energy products in 1∶12 type SmFe permanent magnets，such as multi-site element Co-doping，control of cooling rate，and grain boundary encapsulation，providing important references for developing rare earth permanent magnets.