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Title: NMR characterization of sulphur substitution effects in the KxFe2-ySe2-zSz high-Tc superconductor

We present a⁷⁷ Se NMR study of the effect of S substitution in the high-Tc superconductor KxFe2-ySe2-zSz in a temperature range up to 250 K. We examine two S concentrations, with z=0.8 (Tc~ 26 K) and z=1.6 (nonsuperconducting). The samples containing sulphur exhibit broader NMR line shapes than the KxFe₂Se₂ sample due to local disorder in the Se environment. Our Knight shift ⁷⁷K data indicate that in all samples, uniform spin susceptibility decreases with temperature, and that the magnitude of the Knight shift itself decreases with increased S concentration. In addition, S substitution progressively suppresses low-frequency spin fluctuations. None of the samples exhibit an enhancement of low-frequency antiferromagnetic spin fluctuations near Tc in 1/T₁T, as seen in FeSe.
Authors:
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Publication Date:
OSTI Identifier:
1098744
Type:
Publisher's Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 85; Journal Issue: 14; Journal ID: ISSN 1098-0121
Publisher:
American Physical Society
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English