Unraveling the mark of surface defects on a spinterface: The nitronyl nitroxide/TiO2(110) interface
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Metal-free organic radicals are fascinating materials owing to their unique properties. Having a stable magnetic moment coupled to light elements makes these materials central to develop a large variety of applications. We investigated the magnetic spinterface coupling between the surface of a single rutile TiO2(110) crystal and a pyrene-based nitronyl nitroxide radical, using a combination of thickness-dependent X-ray photoelectron spectroscopy and ab initio calculations. The radicals were physisorbed, and their magnetic character was preserved on the (almost) ideal surface. The situation changed completely when the molecules interacted with a surface defect site upon adsorption. In this case, the reactivity of the defect site led to the quenching of the molecular magnetic moment. Our work elucidates the crucial role played by the surface defects and demonstrates that photoemission spectroscopy combined with density functional theory calculations can be used to shed light on the mechanisms governing complex interfaces, such as those between magnetic molecules and metal oxides.
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Unraveling the mark of surface defects on a spinterface: The nitronyl nitroxide/TiO2(110) interface
Abstract
Metal-free organic radicals are fascinating materials owing to their unique properties. Having a stable magnetic moment coupled to light elements makes these materials central to develop a large variety of applications. We investigated the magnetic spinterface coupling between the surface of a single rutile TiO2(110) crystal and a pyrene-based nitronyl nitroxide radical, using a combination of thickness-dependent X-ray photoelectron spectroscopy and ab initio calculations. The radicals were physisorbed, and their magnetic character was preserved on the (almost) ideal surface. The situation changed completely when the molecules interacted with a surface defect site upon adsorption. In this case, the reactivity of the defect site led to the quenching of the molecular magnetic moment. Our work elucidates the crucial role played by the surface defects and demonstrates that photoemission spectroscopy combined with density functional theory calculations can be used to shed light on the mechanisms governing complex interfaces, such as those between magnetic molecules and metal oxides.
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Acknowledgements
This paper is in loving memory of Daniel Eppacher that contributed to the experiments and their fit analysis. He would have appeared as a second author. RIP Daniel.
The authors thank W. Neu, E. Nadler, H. Adler for technical support, Dr. Sabine Savu for the AFM measurements. Financial support from German Research Foundation (DFG) under the contract CA852/5-1 and CA852/5-2 is gratefully acknowledged. A. C. acknowledges Italian Ministry of Education, Universities and Research (MIUR) for partial founding, through "
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