Microscopic Coexistence of Superconductivity and Antiferromagnetism in Underdoped Ba(Fe1-xRux)2As2

Abstract

We use As-75 nuclear magnetic resonance to investigate the local electronic properties of Ba(Fe1-xRux)(2)As-2 (x = 0.23). We find two phase transitions: to antiferromagnetism at T-N approximate to 60 K and to superconductivity at T-C approximate to 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/T-75(1) is large in the magnetic state, indicating a high density of itinerant electrons induced by Ru doping. On cooling below T-C, 1/T-75(1) on the magnetic sites falls sharply, providing unambiguous evidence for the microscopic coexistence of antiferromagnetism and superconductivity.