Abstract
In iron pnictides, high temperature superconductivity emerges after suppressing antiferromagnetism by doping. Here, we show that antiferromagnetism in is robust against and even enhanced by doping. Using -nuclear magnetic resonance and nuclear quadrupole resonance techniques, we find that an antiferromagnetic order occurs below the Néel temperature K at a high doping concentration where superconductivity sets in at the transition temperature K. In the superconducting state coexisting with antiferromagnetism, the nuclear-spin-lattice relaxation rate becomes proportional to , indicating gapless excitations. Unexpectedly, is enhanced with increasing doping, rising up to K at . The obtained phase diagram of this system enriches the physics of iron-based high- superconductors.
- Received 25 May 2015
- Revised 29 October 2015
DOI:https://doi.org/10.1103/PhysRevB.92.180508
©2015 American Physical Society