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    Exceptionally High Blocking Temperature of 17 K in a Surface-Supported Molecular Magnet
    (Weinheim : Wiley-VCH, 2021) Paschke, Fabian; Birk, Tobias; Enenkel, Vivien; Liu, Fupin; Romankov, Vladyslav; Dreiser, Jan; Popov, Alexey A.; Fonin, Mikhail
    Single-molecule magnets (SMMs) are among the most promising building blocks for future magnetic data storage or quantum computing applications, owing to magnetic bistability and long magnetic relaxation times. The practical device integration requires realization of 2D surface assemblies of SMMs, where each magnetic unit shows magnetic relaxation being sufficiently slow at application-relevant temperatures. Using X-ray absorption spectroscopy and X-ray magnetic circular dichroism, it is shown that sub-monolayers of Dy2 @C80 (CH2 Ph) dimetallofullerenes prepared on graphene by electrospray deposition exhibit magnetic behavior fully comparable to that of the bulk. Magnetic hysteresis and relaxation time measurements show that the magnetic moment remains stable for 100 s at 17 K, marking the blocking temperature TB(100) , being not only in excellent agreement with that of the bulk sample but also representing by far the highest one detected for a surface-supported single-molecule magnet. The reported findings give a boost to the efforts to stabilize and address the spin degree of freedom in molecular magnets aiming at the realization of SMM-based spintronic units.
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    Large-Area Single-Crystal Graphene via Self-Organization at the Macroscale
    (Weinheim : Wiley-VCH, 2020) Ta, Huy Quang; Bachmatiuk, Alicja; Mendes, Rafael Gregorio; Perello, David J.; Zhao, Liang; Trzebicka, Barbara; Gemming, Thomas; Rotkin, Slava V.; Rümmeli, Mark H.
    In 1665 Christiaan Huygens first noticed how two pendulums, regardless of their initial state, would synchronize. It is now known that the universe is full of complex self-organizing systems, from neural networks to correlated materials. Here, graphene flakes, nucleated over a polycrystalline graphene film, synchronize during growth so as to ultimately yield a common crystal orientation at the macroscale. Strain and diffusion gradients are argued as the probable causes for the long-range cross-talk between flakes and the formation of a single-grain graphene layer. The work demonstrates that graphene synthesis can be advanced to control the nucleated crystal shape, registry, and relative alignment between graphene crystals for large area, that is, a single-crystal bilayer, and (AB-stacked) few-layer graphene can been grown at the wafer scale. © 2020 The Authors. Published by Wiley-VCH GmbH