Homogeneous coexistence of superconducting and spin-density-wave states in CaFe_{1-x}Co_{x}AsF as seen via nuclear magnetic resonance

Abstract

We investigated the homogeneous coexistence of spin-density-wave (SDW) and superconducting (SC) states via [75]As-nuclear magnetic resonance (NMR) in CaFe_{1}-xCoxAsF and found that the electronic and magnetic properties of this compound are intermediate between those of LaFeAsO_{1}-xFx and Ba(Fe_{1}-xCox)_{2}As_{2}. For 6% Co-doped samples, the paramagnetic spectral weight completely disappears in the crossover regime between the SDW and SC phases followed by anomalous behavior of relaxation rate (1/T_{1}), implying that the two phases are not segregated. [59]Co-NMR spectra show that spin moments are not commensurate but spatially modulated. These experimental results suggest that incommensurate SDW (IC-SDW) and SC states are compatible in this compound.