Title: Unexpected dependence of the anomalous Hall angle on the Hall conductivity in amorphous transition metal thin films

Abstract

The anomalous Hall effect (AHE), and magnetic and electronic transport properties were investigated in a series of amorphous transition metal thin films— Fe_xS_{i –x}, Fe_xGe_1-x, Co_xGe_1–x, Co_xSi_1–x, and Fe_1–yCo_ySi. The experimental results are compared with density functional theory calculations of the density of Berry curvature and intrinsic anomalous Hall conductivity. In all samples, the longitudinal conductivity (σ_xx), magnetization (M), and Hall resistivity (ρ_xy) increase with increasing transition metal concentration; due to the structural disorder σ_xx is lower in all samples than a typical crystalline metal. In the systems with Fe as the transition metal (including Fe_1–yCo_ySi), the magnetization and AHE are large and in some cases greater than the crystalline analog. In all samples, the AHE is dominated by the intrinsic mechanism, arising from a nonzero, locally derived Berry curvature. The anomalous Hall angle (AHA) (= σ_xy/σ_xx) is as large as 5% at low temperature. These results are compared with the AHAs reported in a broad range of crystalline and amorphous materials. Previous work has shown that in a typical crystalline ferromagnet the Hall conductivity (σ_xy) and σ_xx are correlated and are usually either both large or both small, resulting in an AHA that decreases with increasing σ_xy. By contrast,more » the AHA increases linearly with increasing σ_xy in the amorphous systems. This trend is attributed to a generally low σ_xx, while σ_xy varies and can be large. In the amorphous systems, σ_xx and σ_xy are not coupled, and there may thus exist the potential to further increase the AHA by increasing σ_xy.« less

Authors:

Karel, J. ^[1]; Bouma, D. S. ^[2]; Fuchs, C.  ^[3];

• Search DOE PAGES for author "Fuchs, C."
• Search DOE PAGES for ORCID "0000-0002-4760-6224"

Bennett, S. ^[1]; Corbae, P.  ^[4];

• Search DOE PAGES for author "Corbae, P."
• Search DOE PAGES for ORCID "0000-0002-2259-5557"

Song, S. B. ^[5]; Zhang, B. H. ^[5]; Wu, R. Q. ^[6]; Hellman, F.  ^[2]

• Search DOE PAGES for author "Hellman, F."
• Search DOE PAGES for ORCID "0000-0002-9135-6330"

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+ Show Author Affiliations

1. Monash Univ., Melbourne, VIC (Australia)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
3. Univ. of California, Berkeley, CA (United States); Julius Maximilians Universität, Würzburg (Germany)
4. Univ. of California, Berkeley, CA (United States)
5. Fudan Univ., Shanghai (China)
6. Univ. of California, Irvine, CA (United States)

Publication Date:

Wed Nov 04 00:00:00 EST 2020

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1764546

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review Materials

Additional Journal Information:

Journal Volume: 4; Journal Issue: 11; Journal ID: ISSN 2475-9953

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Electrical conductivity; Electrical generation of spin carriers; Ferromagnetism; Magnetotransport; Spin current; Metallic glasses; Density functional theory