Title: Tuning magnetic order in the van der Waals metal $$Fe_5GeTe_2$$ by cobalt substitution

Abstract

${\mathrm{Fe}}_{5-x}{\mathrm{GeTe}}_2$ is a van der Waals material with one of the highest reported bulk Curie temperatures, $T_{\mathrm{C}}\approx 310\mathrm{K}$. Here, theoretical calculations and experiments are utilized to demonstrate that the magnetic ground state is highly sensitive to local atomic arrangements and the interlayer stacking. Cobalt substitution is found to be an effective way to manipulate the magnetic properties while also increasing the ordering temperature. In particular, cobalt substitution up to $\approx 30\%$ enhances $T_{\mathrm{C}}$ and changes the magnetic anisotropy, while $\approx 50\%$ cobalt substitution yields an antiferromagnetic state. Single crystal x-ray diffraction evidences a structural change upon increasing the cobalt concentration, with a rhombohedral cell observed in the parent material and a primitive cell observed for $\approx 46\%$ cobalt content relative to iron. First-principles calculations demonstrate that it is a combination of high cobalt content and the concomitant change to primitive layer stacking that produces antiferromagnetic order. These results illustrate the sensitivity of magnetism in ${\mathrm{Fe}}_{5-x}{\mathrm{GeTe}}_2$ to composition and structure, and emphasize the important role of local structural order-disorder and layer stacking in cleavable magnetic materials.

Authors:

May, Andrew F.  ^[1];

• Search DOE PAGES for author "May, Andrew F."
• Search DOE PAGES for ORCID "0000-0003-0777-8539"

Du, Mao-Hua  ^[1];

• Search DOE PAGES for author "Du, Mao-Hua"
• Search DOE PAGES for ORCID "0000-0001-8796-167X"

Cooper, Valentino R.  ^[1];

• Search DOE PAGES for author "Cooper, Valentino R."
• Search DOE PAGES for ORCID "0000-0001-6714-4410"

McGuire, Michael A.  ^[1]

• Search DOE PAGES for author "McGuire, Michael A."
• Search DOE PAGES for ORCID "0000-0003-1762-9406"

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+ Show Author Affiliations

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division

Publication Date:

Tue Jul 21 00:00:00 EDT 2020

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division

OSTI Identifier:

1649270

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review Materials

Additional Journal Information:

Journal Volume: 4; Journal Issue: 7; Journal ID: ISSN 2475-9953

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; magnetism