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Author: Büchner, Bernd × End date: 2024 × Start date: 2020 × End date: 2024 × Start date: 2020 × DDC: 660 × Publisher: Weinheim : Wiley-VCH ×

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    Single-Molecule Magnets DyM2N@C80 and Dy2MN@C80 (M=Sc, Lu): The Impact of Diamagnetic Metals on Dy3+ Magnetic Anisotropy, Dy⋅⋅⋅Dy Coupling, and Mixing of Molecular and Lattice Vibrations
    (Weinheim : Wiley-VCH, 2020) Spree, Lukas; Schlesier, Christin; Kostanyan, Aram; Westerström, Rasmus; Greber, Thomas; Büchner, Bernd; Avdoshenko, Stanislav M.; Popov, Alexey A.
    The substitution of scandium in fullerene single-molecule magnets (SMMs) DySc2N@C80 and Dy2ScN@C80 by lutetium has been studied to explore the influence of the diamagnetic metal on the SMM performance of dysprosium nitride clusterfullerenes. The use of lutetium led to an improved SMM performance of DyLu2N@C80, which shows a higher blocking temperature of magnetization (TB=9.5 K), longer relaxation times, and broader hysteresis than DySc2N@C80 (TB=6.9 K). At the same time, Dy2LuN@C80 was found to have a similar blocking temperature of magnetization to Dy2ScN@C80 (TB=8 K), but substantially different interactions between the magnetic moments of the dysprosium ions in the Dy2MN clusters. Surprisingly, although the intramolecular dipolar interactions in Dy2LuN@C80 and Dy2ScN@C80 are of similar strength, the exchange interactions in Dy2LuN@C80 are close to zero. Analysis of the low-frequency molecular and lattice vibrations showed strong mixing of the lattice modes and endohedral cluster librations in k-space. This mixing simplifies the spin–lattice relaxation by conserving the momentum during the spin flip and helping to distribute the moment and energy further into the lattice. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
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    Thermoelectric Properties of Novel Semimetals: A Case Study of YbMnSb2
    (Weinheim : Wiley-VCH, 2020) Pan, Yu; Fan, Feng-Ren; Hong, Xiaochen; He, Bin; Le, Congcong; Schnelle, Walter; He, Yangkun; Imasato, Kazuki; Borrmann, Horst; Hess, Christian; Büchner, Bernd; Sun, Yan; Fu, Chenguang; Snyder, G. Jeffrey; Felser, Claudia
    The emerging class of topological materials provides a platform to engineer exotic electronic structures for a variety of applications. As complex band structures and Fermi surfaces can directly benefit thermoelectric performance it is important to identify the role of featured topological bands in thermoelectrics particularly when there are coexisting classic regular bands. In this work, the contribution of Dirac bands to thermoelectric performance and their ability to concurrently achieve large thermopower and low resistivity in novel semimetals is investigated. By examining the YbMnSb2 nodal line semimetal as an example, the Dirac bands appear to provide a low resistivity along the direction in which they are highly dispersive. Moreover, because of the regular-band-provided density of states, a large Seebeck coefficient over 160 µV K−1 at 300 K is achieved in both directions, which is very high for a semimetal with high carrier concentration. The combined highly dispersive Dirac and regular bands lead to ten times increase in power factor, reaching a value of 2.1 mW m−1 K−2 at 300 K. The present work highlights the potential of such novel semimetals for unusual electronic transport properties and guides strategies towards high thermoelectric performance. © 2020 The Authors. Advanced Materials published by Wiley-VCH GmbH