Magnetotransport in amorphous cobalt silicon and amorphous cobalt germanium thin films

Christopher Fuchs; Dinah Simone Bouma; Zhanghui Chen; Frank Bruni; Arnoud Everhardt; Paul Corbae; Neal Reynolds; Lin-Wang Wang; Frances Hellman

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 Fe_x(Ge,Si)_1-xfilms [1], and the recently shown non-trivial topology in crystalline CoSi [2] suggests a study of amorphous cobalt silicon (a-Co_xSi_1-x) and cobalt germanium (a-Co_xGe_1-x) might lead to advances in the field of topological materials. A comparative study of a-Co_xSi_1-x and a-Co_xGe_1-x thin films has been performed for 0.4<x<0.7. At low temperatures, a-Co_x(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-Fe_x(Ge,Si)_1-x. While the Fe-based alloys show hole carriers, the Co-based alloys show electron carriers. Resistivity measurements show that ρ_xx≥ 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

March 2, 2020, 2:27 PM – March 2, 2020, 2:39 PM

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