Microscopic coexistence of a two-component incommensurate spin density wave with superconductivity in underdoped NaFe0.983Co0.017As

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 ($\ensuremath{\sim}0.2\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{B}$/Fe) and a smaller component with magnetic moment ($\ensuremath{\sim}0.02\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{B}$/Fe). Spin lattice relaxation experiments reveal that this coexistence occurs at a microscopic level.