Element-Specific Magnetism of Thulium-Cyclooctatetraene Nanowires

*Alexander Herman (1), Stefan Kraus (2), Katharina Ollefs (1), Jan Dreiser (3), Florin Radu (4), Thomas Michely (2), Heiko Wende (1)
(1) Universität Duisburg-Essen, Germany, (2) Universität zu Köln, Germany, (3) Paul Scherrer Institut, Switzerland, (4) Helmholtz Zentrum Berlin, Germany

The analysis of the magnetic coupling and the magnetic anisotropy of localized 4f magnetic moments connected via organic ligands in molecular networks is a highly topical field of research owing to potential applications in organic spintronics. Our on-surface synthesis method allows us to synthesize sandwich-molecular nanowires that consist of alternating ring-like cyclooctatetraene (Cot) molecules and varying rare-earth ions. Using thulium hereby offers not only various phases but may also exhibit interesting properties due to its strong single-ion anisotropy compared to e. g. europium. The electronic and magnetic properties of these compounds were studied by X-ray absorption spectroscopy and X-ray magnetic circular dichroism accompanied by a theoretical approach based on multiplet calculations. The X-ray absorption spectroscopy of the systems indicate a 4f12 electronic state of the thulium. In contrast to Eu-cyclooctatetraene nanowires, the XMCD of the Tm systems suggest, that they are not saturated even in high fields and low temperatures. We acknowledge financial support by DFG through the project WE 2623/17-1.