Crystal growth, Magnetic Anisotropy, and Chemical Correlations in Ba<sub>1-x</sub>Na<sub>x</sub>Fe<sub>2</sub>As<sub>2</sub>
ORAL
Abstract
A full understanding of nematicity, magnetic anisotropy, and their connection to superconductivity in hole-doped 122 pnictides requires high-quality crystals and probes sensitive to short-range correlations. We report a study of Ba1-xNaxFe2As2 single crystals that combines the control of stoichiometry with high-field structural and diffuse-scattering measurements.
Crystals grown across a wide composition range show a clear quantitative relationship between the superconducting transition temperature and the sodium content. This trend provides a reliable calibration of the actual Na concentration, indicating that the effective substitution is typically about one half of the nominal value. X-ray diffraction in pulsedmagnetic fields up to 31.4 T applied along the c axis shows that stripe-type spin-density-wave order remains confined to the ab plane. No signatures of detwinning or spin reorientation are observed, confirming strong in-plane magnetic anisotropy and the robustness of the orthorhombic state under such large out-of-plane fields.
Diffuse scattering and three-dimensional ΔPDF analyses reveal the existence of two-dimensional short-range Ba and Na chemical correlations within the ab plane, together with local displacements arising from their size mismatch. These local structural motifs mimic features often attributed to intrinsic nematic fluctuations. Our results elucidate the intrinsic magnetic anisotropy of Ba1-xNaxFe2As2 and show how local compositional order can shape the interpretation of nematic behavior in iron-based superconductors.
Crystals grown across a wide composition range show a clear quantitative relationship between the superconducting transition temperature and the sodium content. This trend provides a reliable calibration of the actual Na concentration, indicating that the effective substitution is typically about one half of the nominal value. X-ray diffraction in pulsedmagnetic fields up to 31.4 T applied along the c axis shows that stripe-type spin-density-wave order remains confined to the ab plane. No signatures of detwinning or spin reorientation are observed, confirming strong in-plane magnetic anisotropy and the robustness of the orthorhombic state under such large out-of-plane fields.
Diffuse scattering and three-dimensional ΔPDF analyses reveal the existence of two-dimensional short-range Ba and Na chemical correlations within the ab plane, together with local displacements arising from their size mismatch. These local structural motifs mimic features often attributed to intrinsic nematic fluctuations. Our results elucidate the intrinsic magnetic anisotropy of Ba1-xNaxFe2As2 and show how local compositional order can shape the interpretation of nematic behavior in iron-based superconductors.
*This work was primarily supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division.
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Presenters
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Omar H Chmaissem
- Northern Illinois University