Dresden 2020 – scientific programme
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DS: Fachverband Dünne Schichten
DS 44: Magnetic Coupling and Anisotropy in Thin Films (joint session MA/DS)
DS 44.2: Talk
Friday, March 20, 2020, 09:45–10:00, HSZ 04
Complex spin textures and domain-wall pinning in Sm-Co magnets — Leonardo Pierobon1, András Kovács2, Robin E. Schäublin1, Stephan S. A. Gerstl1, Urs Wyss3, •Jan Caron2, Rafal E. Dunin-Borkowski2, Jörg F. Löffler1, and Michalis Charilaou1 — 1Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, Switzerland — 2Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, FZ Julich, Germany — 3Arnold Magnetic Technologies, Switzerland
Sm-Co alloys are the best-performing permanent magnets at high temperatures due to their cellular microstructure, which consists of a Sm2Co17 matrix and SmCo5 cells intersected by Zr-rich platelets. Although extensive research has been done to understand the connection between the magnet's microstructure and its magnetic properties, theory and experiments have still not converged. To tackle this issue, we use Lorentz transmission electron microscopy, off-axis electron holography and micromagnetic simulations. We find that the magnetization reversal starts by domain-wall nucleation at the interfaces between Zr-rich platelets and the Sm2Co17 matrix. Despite strong pinning at the SmCo5 cells, curling instabilities form where all three phases meet, further propagating the reversal. Unexpectedly, we also find topologically non-trivial structures with 2π winding that significantly affect the reversal. Based on this, we propose a modification of microstructure to increase the coercivity and remanence.