[P1] Processing, Characterization & Thin Films

[P1-56] Spectroscopic insights into the electronic structure of non-critical rare earth containing permanent magnets

*Benedikt Eggert¹, Alex Aubert², Philipp Klaßen¹, Janosch Tasto¹, Nathan Yutronkie³, Fabrice Wilhelm³, Andrei Rogalev³, Konstantin Skokov², Heiko Wende¹, Oliver Gutfleisch², Katharina Ollefs¹ (1. University of Duisburg-Essen (Germany), 2. Technical University of Darmstadt (Germany), 3. European Synchrotron Radiation Facility (France))

Keywords:

X-ray absorption spectroscopy,Ce based compounds,X-ray magnetic circular dichroism

The extensive use of critical rare-earth elements like Nd and Sm in magnet production raises concerns about their limited availability. Ongoing research explores the feasibility of cost-effective hard magnetic materials by substituting Nd or Sm with more abundant rare-earth elements such as Ce or La [2]. Here, it is crucial to deepen the understanding of compounds' electronic and magnetic structures consisting of these low-cost rare-earth elements.Within this contribution, we focus on investigating the magnetic properties and electronic structures of Ce-containing permanent magnets in compounds such as (Nd,Ce)₂Fe₁₄B [3], CeCo₅ [4], or CeFe₁₁Ti [5]. Therefore, we employ advanced spectroscopic techniques, for example, X-ray absorption spectroscopy or X-ray magnetic circular dichroism, by probing the rare earth L2,3 and transition metal K edges. With this spectroscopic approach, we gain element-specific insights into the electronic structure and resolve the magnetic properties of each element in these systems. In particular, we will show how Ce's valence state can be manipulated, e.g., by modifying its local surroundings. Here, we will show that adding Cu in CeCo₅ compounds leads to the formation of a Cu-rich region, resulting in a paramagnetic Ce³⁺ state that can act as a pinning site of domain walls. In the CeFe₁₁Ti system, introducing interstitial N leads to an enhanced Kondo screening of the 4f electrons [5], resulting in a reduction of the magnetic anisotropy.

We acknowledge the financial support through the Deutsche Forschungsgemeinschaft within the framework of the CRC/TRR270 HoMMage (Project 405553726-TRR270), the BMBF (05K2019 and 05K2022), and we thank the ESRF for allocation of beamtime at beamline ID12 within projects HC-4051 & MA-5882.

References
[1] O. Gutfleisch et al. Adv. Mater. 23, 821-842 (2011)
[2] K. P. Skokov et al. Scripta Materialia, 154, 289-294 (2018)
[3] Y. Wu et al. Acta Materialia, 235, 118062 (2022)
[4] H. Shishido J. Magn. Magn. Mater. 562, 169748 (2022)
[5] A. Galler et al. npj Quantum Materials 6, 2 (2021)