Presentation Information
[P2-36]Microstructural Building Blocks Governing the High-Coercivity State in SmCo-Based Magnets: Searching for the “Weak Link” and the “Perfect Defect”
*Konstantin P Skokov1, Alex Aubert1, Burcak Ekitli1, Esmaeil Adabifiroozjaei1, Leopoldo Molina-Luna1, Yangiywei Yang1, Baixiang Xu1, Nikita Polin2, Baptiste Gault2, Michael Farle3, Oliver Gutfleisch1 (1. Technische Universität Darmstadt (Germany), 2. Max-Planck Institute for Sustainable Materials (Germany), 3. University of Duisburg-Essen (Germany))
Keywords:
Sm-Co-based permanent manets,microstructure,coercivity mechanisms
Commercial SmCoFeCuZr-based sintered magnets usually contain multiple chemical elements and exhibit a highly complex microstructure, consisting of various phases - many at the nanometer scale with internal concentration gradients. This structural complexity complicates efforts to determine which features primarily contribute to high coercivity. As a result, an ongoing debate continues within the scientific community about which specific nanostructural components are critical for achieving highest coercivity and which play a secondary role in the development of optimal magnetic performance. As part of the Collaborative Research Centre / Transregio 270 HoMMage, our team aims to revisit the fundamental aspects of this material system by conducting a systematic study on model samples with a deliberately simplified chemical composition. By restricting the number of alloying elements to a minimum, we seek to isolate and reproduce specific microstructural components characteristic of the complex architecture found in commercial magnets. This approach allows us to examine the correlation between the structural features of these simplified systems and their resulting magnetic properties, providing deeper insight into the fundamental mechanisms governing coercivity. One of the key aspects of our study is the investigation of single-grain magnets, also known as quasi-single crystals, in which highly coercive inclusions are formed in a 1:5 or 2:17 (Sm:Co) matrix through annealing. This approach helped us to exclude grain boundary phases and texture imperfections from the consideration. Our study started with the Ce(CoCu)5 and Sm(CoCu)5 compounds, focusing on the detailed examination of Cu-rich pinning sites within the 1:5 matrix. We systematically analyzed their chemical composition, morphology, microstructure and local magnetic properties to better understand their role in enhancing coercivity. Further, we investigated the effect of zirconium by examining the nanostructure of SmCo7.7 and SmCo7.7-xZrx compositions. Our results show that in the absence of copper, Zr promotes the development of a cellular microstructure similar to that found in commercial SmZrCoCuFe magnets. The presence of copper is necessary to achieve good hard magnetic properties. In the final part of the talk, we present our study on the microstructure of a commercial Sm(Co,Fe,Cu,Zr)7±δ sintered magnet in which we address the concept of the 'perfect defect' - identifying which structural components play a crucial role in extrinsic and intrinsic origin of coercivity and which serve only a secondary, auxiliary function.
This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Project-ID 405553726
[1] M. Duerrschnabel, et al. Atomic structure and domain wall pinning in samarium-cobalt-based permanent magnets. Nature Communications 8, 1–7 (2017).
[2] N. Polin et al., Formation of cellular/lamellar nanostructure in Sm2Co17-type binary and ternary Sm-Co-Zr magnets, Scripta Materialia, 258, 116530 (2025)
This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Project-ID 405553726
[1] M. Duerrschnabel, et al. Atomic structure and domain wall pinning in samarium-cobalt-based permanent magnets. Nature Communications 8, 1–7 (2017).
[2] N. Polin et al., Formation of cellular/lamellar nanostructure in Sm2Co17-type binary and ternary Sm-Co-Zr magnets, Scripta Materialia, 258, 116530 (2025)