Title: Lattice disorder effect on magnetic ordering of iron arsenides

Abstract

This study investigates magnetic ordering temperature in nano- and mesoscale structural features in an iron arsenide. Although magnetic ground states in quantum materials can be theoretically predicted from known crystal structures and chemical compositions, the ordering temperature is harder to pinpoint due to potential local lattice variations that calculations may not account for. In this work we find surprisingly that a locally disordered material can exhibit a significantly larger Néel temperature (T_N) than an ordered material of precisely the same chemical stoichiometry. Here, a EuFe₂As₂ crystal, which is a ‘122’ parent of iron arsenide superconductors, is found through synthesis to have ordering below T_N = 195 K (for the locally disordered crystal) or T_N = 175 K (for the ordered crystal). In the higher T_N crystals, there are shorter planar Fe-Fe bonds [2.7692(2) Å vs. 2.7745(3) Å], a randomized in-plane defect structure, and diffuse scattering along the [00 L] crystallographic direction that manifests as a rather broad specific heat peak. For the lower T_N crystals, the a-lattice parameter is larger and the in-plane microscopic structure shows defect ordering along the antiphase boundaries, giving a larger T_N and a higher superconducting temperature (T_c) upon the application of pressure. First-principles calculations findmore » a strong interaction between c-axis strain and interlayer magnetic coupling, but little impact of planar strain on the magnetic order. Neutron single-crystal diffraction shows that the low-temperature magnetic phase transition due to localized Eu moments is not lattice or disorder sensitive, unlike the higher-temperature Fe sublattice ordering. This study demonstrates a higher magnetic ordering point arising from local disorder in 122.« less

Authors:

Sefat, Athena Sefa  ^[1];

• Search DOE PAGES for author "Sefat, Athena Sefa"
• Search DOE PAGES for ORCID "0000-0002-5596-3504"

Wang, Xiaoping P.  ^[1];

• Search DOE PAGES for author "Wang, Xiaoping P."
• Search DOE PAGES for ORCID "0000-0001-7143-8112"

Liu, Yaohua  ^[1];

• Search DOE PAGES for author "Liu, Yaohua"
• Search DOE PAGES for ORCID "0000-0002-5867-5065"

Zou, Qiang  ^[1];

• Search DOE PAGES for author "Zou, Qiang"
• Search DOE PAGES for ORCID "0000-0002-0912-6895"

Fu, Mimgming ^[1]; Gai, Zheng  ^[1];

• Search DOE PAGES for author "Gai, Zheng"
• Search DOE PAGES for ORCID "0000-0002-6099-4559"

Ganesan, Kalaiselvan ^[2]; Vohra, Yogesh ^[2]; Li, Li  ^[1];

• Search DOE PAGES for author "Li, Li"
• Search DOE PAGES for ORCID "0000-0003-1683-8118"

Parker, David S.  ^[1]

• Search DOE PAGES for author "Parker, David S."
• Search DOE PAGES for ORCID "0000-0001-6101-1334"

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+ Show Author Affiliations

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Univ. of Alabama, Birmingham, AL (United States)

Publication Date:

Fri Dec 27 00:00:00 EST 2019

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division

OSTI Identifier:

1606710

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Scientific Reports

Additional Journal Information:

Journal Volume: 9; Journal Issue: 1; Journal ID: ISSN 2045-2322

Publisher:

Nature Publishing Group

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; condensed-matter physics; materials science