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arXiv · 1112.0484

Magnetism and superconductivity in Eu0.2Sr0.8(Fe0.86Co0.14)2As2 probed by 75As NMR

R. Sarkar·R. Nath·P. Khuntia·H. S. Jeevan·P. Gegenwart·M. Baenitz
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Abstract

We report bulk superconductivity (SC) in Eu$_{0.2}$Sr$_{0.8}$(Fe$_{0.86}$Co$_{0.14}$)$_{2}$As$_{2}$ single crystals by means of electrical resistivity, magnetic susceptibility, and specific heat measurements with $T$$_{\mathrm{c}}$ $\simeq$ 20 K with an antiferromagnetic (AFM) ordering of Eu$^{2+}$ moments at $T$$_{\mathrm{N}}$ $\simeq$ 2.0 K in zero field. $^{75}$As NMR experiments have been performed in the two external field directions (H$\|ab$) and (H$\|c$). $^{75}$As-NMR spectra are analyzed in terms of first order quadrupolar interaction. Spin-lattice relaxation rates (1/$T_{1}$) follow a $T^{3}$ law in the temperature range 4.2-15 K. There is no signature of Hebel-Slichter coherence peak just below the SC transition indicating a non s-wave or s$_{\pm}$ type of superconductivity. The increase of 1/$T_{1}T$ with lowering the temperature in the range 160-18 K following $\frac{C}{T+θ}$ law reflecting 2D AFM spin fluctuations.

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R. Sarkar, R. Nath, P. Khuntia, H. S. Jeevan, P. Gegenwart, M. Baenitz. 2011-12-02. Magnetism and superconductivity in Eu0.2Sr0.8(Fe0.86Co0.14)2As2 probed by 75As NMR. https://doi.org/10.1088/0953-8984%2F24%2F4%2F045702

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