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    Robust Magnetic Order Upon Ultrafast Excitation of an Antiferromagnet
    (Weinheim : Wiley-VCH, 2022) Lee, Sang‐Eun; Windsor, Yoav William; Fedorov, Alexander; Kliemt, Kristin; Krellner, Cornelius; Schüßler‐Langeheine, Christian; Pontius, Niko; Wolf, Martin; Atxitia, Unai; Vyalikh, Denis V.; Rettig, Laurenz
    The ultrafast manipulation of magnetic order due to optical excitation is governed by the intricate flow of energy and momentum between the electron, lattice, and spin subsystems. While various models are commonly employed to describe these dynamics, a prominent example being the microscopic three temperature model (M3TM), systematic, quantitative comparisons to both the dynamics of energy flow and magnetic order are scarce. Here, an M3TM was applied to the ultrafast magnetic order dynamics of the layered antiferromagnet GdRh2Si2. The femtosecond dynamics of electronic temperature, surface ferromagnetic order, and bulk antiferromagnetic order were explored at various pump fluences employing time- and angle-resolved photoemission spectroscopy and time-resolved resonant magnetic soft X-ray diffraction, respectively. After optical excitation, both the surface ferromagnetic order and the bulk antiferromagnetic order dynamics exhibit two-step demagnetization behaviors with two similar timescales (<1 ps, ∼10 ps), indicating a strong exchange coupling between localized 4f and itinerant conduction electrons. Despite a good qualitative agreement, the M3TM predicts larger demagnetization than the experimental observation, which can be phenomenologically described by a transient, fluence-dependent increased Néel temperature. The results indicate that effects beyond a mean-field description have to be considered for a quantitative description of ultrafast magnetic order dynamics.
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    Spin Hall effect emerging from a noncollinear magnetic lattice without spin-orbit coupling
    (Bristol : Institute of Physics Publishing, 2018) Zhang, Y.; Železný, J.; Sun, Y.; Van Den Brink, J.; Yan, B.
    The spin Hall effect (SHE), which converts a charge current into a transverse spin current, has long been believed to be a phenomenon induced by spin-orbit coupling. Here, we identify an alternative mechanism to realize the intrinsic SHE through a noncollinear magnetic structure that breaks the spin rotation symmetry. No spin-orbit coupling is needed even when the scalar spin chirality vanishes, different from the case of the topological Hall effect and topological SHE reported previously. In known noncollinear antiferromagnetic compounds Mn3X (X = Ga, Ge, and Sn), for example, we indeed obtain large spin Hall conductivities based on ab initio calculations.