Microscopic coexistence of a two-component incommensurate spin density wave with superconductivity in underdoped NaFe${}_{0.983}$Co${}_{0.017}$As

Abstract

We have performed ${}^{75}$As and ${}^{23}$Na nuclear magnetic resonance (NMR) measurements on a single crystal of NaFe${}_{0.9835}$Co${}_{0.0165}$As and found microscopic coexistence of superconductivity with a two-component spin density wave (SDW). Using ${}^{23}$Na NMR we measured the spatial distribution of local magnetic fields. The SDW was found to be incommensurate with a major component having magnetic moment ($\sim 0.2{\mu }_B$/Fe) and a smaller component with magnetic moment ($\sim 0.02{\mu }_B$/Fe). Spin lattice relaxation experiments reveal that this coexistence occurs at a microscopic level.

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