Homogeneous coexistence of SDW and SC states in CaFe(1-x)Co(x)AsF studied by nuclear magnetic resonance

TL;DR

This study uses 75As-NMR to demonstrate that in CaFe(1-x)Co(x)AsF, incommensurate SDW and superconducting states coexist homogeneously, revealing a complex interplay of magnetic and electronic properties.

Contribution

It provides direct NMR evidence that incommensurate SDW and SC states coexist homogeneously in CaFe(1-x)Co(x)AsF, a novel finding in iron-based superconductors.

Findings

Homogeneous coexistence of SDW and SC states in CaFe(1-x)Co(x)AsF.

Incommensurate SDW characterized by spatially modulated spin moments.

Electronic and magnetic properties are intermediate between LaFeAsO(1-x)F(x) and Ba(Fe(1-x)Co(x))2As2.

Abstract

We investigated the homogeneous coexistence of spin-density-wave (SDW) and superconducting (SC) states via 75As-nuclear magnetic resonance (NMR) in CaFe(1-x)Co(x)AsF and found that the electronic and magnetic properties of this compound are intermediate between those of LaFeAsO(1-x)F(x) and Ba(Fe(1-x)Co(x))2As2. For 6% Co-doped samples, the paramagnetic spectral weight completely disappears in the crossover regime between the SDW and SC phases followed by the anomalous behavior of relaxation rate (1/T1), implying that the two phases are not segregated. The 59Co-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.