Long Ma, G. F. Ji, Jia Dai, X. R. Lu, M. J. Eom, J. S. Kim, B. Normand, Weiqiang Yu
We use 75As nuclear magnetic resonance (NMR) to investigate the local electronic properties of underdoped Ba(Fe1-xRux)2As2 (x = 0.23). We find two phase transitions, to antiferromagnetism at T_N \approx 60 K and to superconductivity at T_C \approx 15 K. Below T_N, our data show that the system is fully magnetic, with a commensurate antiferromagnetic structure and a moment of 0.4\mu_B/Fe. The spin-lattice relaxation rate 1/^{75}T1 is large in the magnetic state, indicating a high density of itinerant electrons induced by Ru doping. On cooling below T_C, 1/^{75}T_1 on the magnetic sites falls precipitously, providing unambiguous evidence for the microscopic coexistence of antiferromagnetism and superconductivity.
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http://arxiv.org/abs/1205.3270
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