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- ItemTerahertz spin currents and inverse spin Hall effect in thin-film heterostructures containing complex magnetic compounds(Singapore [u.a.] : World Scientific Publishing, 2017-08-23) Seifert, T.; Martens, U.; Günther, S.; Schoen, M.A.W.; Radu, F.; Chen, X.Z.; Lucas, I.; Ramos, R.; Aguirre, M.H.; Algarabel, P.A.; Anadón, A.; Körner, H.; Walowski, J.; Back, C.; Ibarra, M.R.; Morellón, L.; Saitoh, E.; Wolf, M.; Song, C.; Uchida, K.; Münzenberg, M.; Radu, I.; Kampfrath, T.Terahertz emission spectroscopy (TES) of ultrathin multilayers of magnetic and heavy metals has recently attracted much interest. This method not only provides fundamental insights into photoinduced spin transport and spin–orbit interaction at highest frequencies, but has also paved the way for applications such as efficient and ultrabroadband emitters of terahertz (THz) electromagnetic radiation. So far, predominantly standard ferromagnetic materials have been exploited. Here, by introducing a suitable figure of merit, we systematically compare the strength of THz emission from X/Pt bilayers with X being a complex ferro-, ferri- and antiferromagnetic metal, that is, dysprosium cobalt (DyCo5), gadolinium iron (Gd24Fe76), magnetite (Fe3O4) and iron rhodium (FeRh). We find that the performance in terms of spin-current generation not only depends on the spin polarization of the magnet’s conduction electrons, but also on the specific interface conditions, thereby suggesting TES to be a highly interface-sensitive technique. In general, our results are relevant for all applications that rely on the optical generation of ultrafast spin currents in spintronic metallic multilayers.
- ItemEvidence 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.