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

*Funded by U.S. DOE, Contract No. DE-AC02-05-CH11231 (NEMM, MSMAG)

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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