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Itinerant ferromagnetism and intrinsic anomalous Hall effect in amorphous iron-germanium

ORAL

Abstract

The amorphous iron-germanium system (a-FexGe1-x) lacks long-range structural order and hence lacks a meaningful Brillouin zone. The magnetization of a-FexGe1-x is well explained by the Stoner model for x ≥ 0.4, indicating that the local order of the amorphous structure preserves the spin-split density of states of the Fe-3d states sufficiently to polarize the electronic structure despite k being a bad quantum number. Measurements show an enhanced anomalous Hall resistivity relative to crystalline FeGe; comparison to density functional theory calculations of the anomalous Hall conductivity (AHC) resolves its underlying mechanisms. The intrinsic mechanism, typically understood as the Berry curvature integrated over occupied k-states but equivalent to the density of curvature (DOC) integrated over occupied energies, dominates the AHC of a-FexGe1-x (0.38 ≤ x ≤ 0.61). The DOC is the sum of spin-orbit correlations of local orbital states and can hence be calculated with no reference to k. This result and the accompanying Stoner-like model for the intrinsic AHC establish a unified understanding of the physics of the anomalous Hall effect in both crystalline and disordered systems.
D. S. Bouma et al., arXiv:1908.06055, 2019

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Presenters

  • Neal Reynolds

    University of California, Berkeley, and Lawrence Berkeley National Laboratory, University of California, Berkeley and Lawrence Berkeley National Laboratory

Authors

  • Dinah Simone Bouma

    Physics, University of California, Berkeley, University of California, Berkeley, and Lawrence Berkeley National Laboratory, University of California Berkeley, University of California, Berkeley and Lawrence Berkeley National Laboratory

  • Neal Reynolds

    University of California, Berkeley, and Lawrence Berkeley National Laboratory, University of California, Berkeley and Lawrence Berkeley National Laboratory

  • Zhanghui Chen

    Lawrence Berkeley National Laboratory

  • Frank Bruni

    University of California, Berkeley

  • Binhua Zhang

    Fudan University

  • Michael Flatté

    Optical Science and Technology Center and Department of Physics, The University of Iowa, Department of Physics and Astronomy, University of Iowa, University of Iowa, Univ of Iowa, University of Iowa, University of Chicago, and Eindhoven University of Technology, Physics and Astronomy, University of Iowa, Department of Physics and Astronomy, The University of Iowa

  • Robert Streubel

    Lawrence Berkeley National Laboratory

  • Lin-Wang Wang

    Materials Science Division, Lawrence Berkeley National Laboratory, Lawrence Berkeley National Laboratory

  • Ruqian Wu

    UCI, University of California, Irvine, Department of Physics and Astronomy, University of California, Irvine

  • Frances Hellman

    Physics, University of California, Berkeley, University of California, Berkeley, University of California, Berkeley, and Lawrence Berkeley National Laboratory, University of California Berkeley, University of California, Berkeley and Lawrence Berkeley National Laboratory