High magnetic energy product in isotropic nanocomposite powders with high percent of soft phase towards ultrastrong magnets

Nanostructure of magnetically hard and soft materials is fascinating for exploring next-generation ultrastrong permanent magnets with less expensive rare-earth elements. However, the resulting hard/soft nanocomposites often exhibit a low remanence/energy product due to the challenge in obtaining ideal phase components and appropriate soft phase fraction. In this work, a novel microstructure of multiple hard phases consisted of SmCo5 and SmCo3 as main phase, SmCo7 and Sm2Co17 as minor phase and a high ratio of FeCo (27 wt.%-48 wt.%) as soft phase was obtained. The grain size of both hard and soft phase below 15 nm was observed. The optimal energy product for Sm-Co/Fe(Co) nanocomposite is 2.1 times (an increase of 107%) of the corresponding single-hard-phase powders without soft phase. It reports that the isotropic nanocomposite powders exhibit a new record of magnetic energy product larger than 25 MGOe (the highest value is 28.6 MGOe). The high performance and the microstructure achieved in this work for the isotropic powders will shed light on and provide a good premise for synthesizing high performance anisotropic bulk nanocomposite magnets.