Influence of amorphous phase on coercivity in SmCo5-Cu nanocomposites

Authors: Franziska Staab, Yangyiwei Yang, Eren Foya, Enrico Bruder, Benjamin Zingsem, Esmaeil Adabifiroozjaei, Despoina Nasiou, Konstantin Skokov, David Koch, Michael Farle, Rafal E. Dunin-Borkowski, Leopoldo Molina-Luna, Oliver Gutfleisch, Bai-Xiang Xu, Karsten Durst

Severe plastic deformation of powder blends consisting of SmCo₅-Cu results in magnetically hardened nanocomposite bulk materials. Previously it was reported that the microstructure is continuously refined with increasing deformation, yet, coercivity saturates at a certain level of strain and partial amorphization of the SmCo₅ phase is observed. In this work larger strains, over the range of the previous work are applied showing further structural refinement but a strong decrease in coercivity. Micromagnetic simulations based on the experimentally observed microstructure serve to clarify the effect of amorphization in the SmCo₅ phase and disclose the detrimental character of the amorphous phase. For a fixed volume fraction of nanocrystals the simulations reveal an increasing coercivity with decreasing the size of them due to increasing number of interfaces acting as pinning sites. Furthermore, our micromagnetic simulations disclose the mechanisms of saturation and decline of magnetic hardening due to the strain induced by high-pressure torsion.