XMCD Investigations of Lanthanide Magnetic Molecular Systems

X-ray Magnetic Circular Dichroism (XMCD) an X-ray absorption spectroscopy that provides inter alia insights into unequal population of the 4f shell in magnetic lanthanide (Ln) compounds. It combines magnetic sensitivity with chemical specificity and is especially valuable for studying magnetic properties of Ln and transition metal compounds. This is demonstrated through two examples:
The Ln bis-phthalocyanine (Pc)2 system has inspired numerous studies from past to present and continues to pose fascinating questions. Depending on the central Ln, these compounds range from diamagnetic species to SMMs. Multilayer samples2 of TbPc2, ErPc2 and YbPc2 were sublimed onto polycrystalline Molybdenum platelets and investigated at the Ln M4,5-edges and the N K-edge.
A system of bimetallic Dy-Co compounds is particularly useful to study the effects of metal-metal coupling on single molecular magnet (SMM) behaviour.1 Diamagnetic substitution can introduce or exclude such effects. Therefore we studied CoII(btmp)2(µ-piv)DyIII(piv)2, CoII(btmp)2(µ-piv)YIII(piv)2, and ZnII(btmp)2(µ-piv)DyIII(piv)2 ground to powders and pressed into In foil at the Co L2,3 and Dy M4,5¬ edges. ... mehrOur experiments were performed at the WERA Beamline at the KIT Light Source, Karlsruhe, Germany3 and at the BL 6.3.1. of the Advanced Light Source, Berkeley, USA.4
XMCD results will be compared to classical magnetometry data.5 In the LnPc₂ system, XMCD enables differentiation between spin and orbital magnetic contributions.6 Additionally, in the bimetallic system, the element-specific nature of XMCD allows magnetic interactions to be examined from both metal centers independently.
References
(1) Pfleger, R. F. et al. Chem. – A Eur. J. 2025, 31 (7), e202403002.
(2) Dreiser, J. J. Phys. Condens. Matter 2015, 27 (18).
(3) Nagel, P. et al. Soft X-Ray Beamline WERA; 2007.
(4) Beamline 6.3.1 https://als.lbl.gov/beamlines/6-3-1/#6-3-1 (accessed Jul 11, 2025).
(5) Ishikawa, N. et al. Inorg. Chem. 2003, 42 (7), 2440–2446.
(6) Ramanantoanina, H. et al. Chem. Commun. 2019, 55 (20), 2988–2991.

Acknowledgements:
We thank the Institute for Beam Physics and Technology (IBPT, KIT) for the operation of the storage ring, the Karlsruhe Research Accelerator (KARA). This research used resources of Beamline 6.3.1. of the Advanced Light Source, a U.S. DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. The authors gratefully acknowledge financial support from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through the Collaborative Research Centre ″4f for Future” Schacherl junior research group and project Z (CRC 1573, project number 471424360).