Regensburg 2022 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 26: Molecular Magnetism

MA 26.4: Vortrag

Mittwoch, 7. September 2022, 15:45–16:00, H48

High-frequency EPR studies on monomeric 4f complexes — Lena Spillecke, Changhyun Koo, and •Rüdiger Klingeler — Kirchhoff Institute for Physics, Heidelberg University, Germany

Tuning of magnetic anisotropy by appropriate design of crystal fields in 4f monomeric complexes is guided by experimental determination of relevant parameters – here by high-frequency electron paramagnetic resonance (HF-EPR) studies – and by numerical results. Our recent study on pentagonal-bipyramidal Er(III) [1] complexes is motivated by a reported difference in relaxation behavior [2]. Evaluating the data in a S = 1/2 pseudo spin approximation for each Kramers doublet (KD) results in the precise determination of the crystal field splitting energies and effective g-values of the three lowest KDs. Relaxation behaviour is directly traced back to changes in electronic structure, induced by the crystal field and are attributed to a pronounced non-axiality of the ground-state g-tensor promoting a fast QTM magnetic relaxation. Another confirmation of a guided approach is provided by recent data on a set of [Ln(III)L12]-complexes (Ln = Dy, Tb) involving tetradentate ligands [3] as well as by studies of a novel nonadentate bispidine-based ligand where the experimentally determined relaxation barrier of 46 cm⁻¹ is rather modest but in excellent agreement with that predicted by ab-initio calculations [4].

[1]L. Spillecke et al., Dalton Transactions 50, 18143 (2021) [2]T.A. Bazhenova et al., Molecules 26, 6908 (2021) [3]P. Comba et al., Chemistry-Eur. J. 24, 5319 (2018) [4]P. Cieslik et al., J of Inorg. Gen. Chem. (Z. Anorg. Allg. Chem.) 647, 843 (2021)