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Publisher: Washington, DC : ACS × Subject: Rare earths ×

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Now showing 1 - 2 of 2
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    Oxygen-deficient oxide growth by subliming the oxide source material: The cause of silicide formation in rare earth oxides on silicon
    (Washington, DC : ACS, 2013) Bierwagen, O.; Proessdorf, A.; Niehle, M.; Grosse, F.; Trampert, A.; Klingsporn, M.
    The fundamental issue of oxygen stoichiometry in oxide thin film growth by subliming the source oxide is investigated by varying the additionally supplied oxygen during molecular beam epitaxy of RE2O3 (RE = Gd, La, Lu) thin films on Si(111). Supplying additional oxygen throughout the entire growth was found to prevent the formation of rare earth silicides observed in films grown without an oxygen source. Postgrowth vacuum annealing of oxygen stoichiometric films did not lead to silicide formation thereby confirming that the silicides do not form as a result of an interface instability at growth temperature in vacuum but rather due to an oxygen deficiency in the source vapor. The average oxygen deficiency of the rare-earth containing species in the source vapor was quantified by the 18O tracer technique and correlated with that of the source material, which gradually decomposed during sublimation. Therefore, any oxide growth by sublimation of the oxide source material requires additional oxygen to realize oxygen stoichiometric films.
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    Evidence of the Anomalous Fluctuating Magnetic State by Pressure-Driven 4f Valence Change in EuNiGe3
    (Washington, DC : ACS, 2023) Chen, K.; Luo, C.; Zhao, Y.; Baudelet, F.; Maurya, A.; Thamizhavel, A.; Rößler, U. K.; Makarov, D.; Radu, F.
    In rare-earth compounds with valence fluctuation, the proximity of the 4f level to the Fermi energy leads to instabilities of the charge configuration and the magnetic moment. Here, we provide direct experimental evidence for an induced magnetic polarization of the Eu3+ atomic shell with J = 0, due to intra-atomic exchange and spin-orbital coupling interactions with the Eu2+ atomic shell. By applying external pressure, a transition from antiferromagnetic to a fluctuating behavior in EuNiGe3 single crystals is probed. Magnetic polarization is observed for both valence states of Eu2+ and Eu3+ across the entire pressure range. The anomalous magnetism is discussed in terms of a homogeneous intermediate valence state where frustrated Dzyaloshinskii-Moriya couplings are enhanced by the onset of spin-orbital interaction and engender a chiral spin-liquid-like precursor.