NMR characterization of sulphur substitution effects in the K_xFe_2-ySe_2-xS_z high-T_c superconductor

Journal Article · Tue Apr 17 00:00:00 EDT 2012 · Phys. Rev. B

DOI:https://doi.org/10.1103/PhysRevB.85.144516· OSTI ID:1081151

Torchetti, D. A. ^[1]; Imai, T. ^[2]; Lei, H. C. ^[3]; Petrovic, C. ^[3]

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1. McMaster Univ., Hamilton, ON (Canada)
2. McMaster Univ., Hamilton, ON (Canada); Canadian Inst. for Advanced Research, Ontario (Canada)
3. Brookhaven National Lab. (BNL), Upton, NY (United States)

We present a ⁷⁷Se NMR study of the effect of S substitution in the high-T_c superconductor K_xFe_2-ySe_2-zS_z in a temperature range up to 250 K. We examine two S concentrations, with z=0.8 (T_c~ 26 K) and z=1.6 (nonsuperconducting). The samples containing sulphur exhibit broader NMR line shapes than the K_xFe₂Se₂ 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 T_c in 1/T₁T, as seen in FeSe.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Center for Emergent Superconductivity (CES)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1081151
• Journal Information: Phys. Rev. B, Vol. 85; Related Information: CES partners with Brookhaven National Laboratory (BNL); Argonne National Laboratory; University of Illinois, Urbana-Champaign; Los Alamos National Laboratory
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

phonons
thermal conductivity
energy storage (including batteries and capacitors)
superconductivity
defects
spin dynamics