Magnetotransport in amorphous cobalt silicon and amorphous cobalt germanium thin films

ORAL

Abstract

The transition-metal group IV compounds iron germanium and iron silicon show ferromagnetic properties in amorphous Fex(Ge,Si)1-x films [1], and the recently shown non-trivial topology in crystalline CoSi [2] suggests a study of amorphous cobalt silicon (a-CoxSi1-x) and cobalt germanium (a-CoxGe1-x) might lead to advances in the field of topological materials. A comparative study of a-CoxSi1-x and a-CoxGe1-x thin films has been performed for 0.4<x<0.7. At low temperatures, a-Cox(Ge,Si)1-x shows no magnetism for x<0.6 and weak ferromagnetism above x≈0.6, well over an order of magnitude smaller than in a-Fex(Ge,Si)1-x. While the Fe-based alloys show hole carriers, the Co-based alloys show electron carriers. Resistivity measurements show that ρxx ≥ 150µΩcm and dependents mainly on the carrier concentration, which is characteristic for amorphous metals. Hall measurements probe whether the anomalous Hall effect stems from the intrinsic (Berry curvature) mechanism, equal to the integral over occupied energy states of the density of Berry curvature, which is the sum of the spin-orbit correlations of local orbital states [1].

[1] Bouma et al, arXiv:1908.06055, 2019
[2] Takane et al, Phys.Rev.Lett. 122-076402, 2019

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

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Presenters

  • Christopher Fuchs

    • University of California, Berkeley and University of Wurzburg

Authors

  • Christopher Fuchs

    • University of California, Berkeley and University of Wurzburg

  • 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

  • Zhanghui Chen

    • Lawrence Berkeley National Laboratory

  • Frank Bruni

    • University of California, Berkeley

  • Arnoud Everhardt

    • University of California, Berkeley

  • Paul Corbae

    • University of California, Berkeley

  • Neal Reynolds

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

  • Lin-Wang Wang

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

  • 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