75As NMR Study of Hole-Doped Superconductor Ba1-xKxFe2As2 (Tc = 38K)

TL;DR

This study uses 75As NMR to investigate the microscopic phase separation and magnetic fluctuations in the hole-doped superconductor Ba1-xKxFe2As2 with Tc of 38K, revealing key insights into its magnetic and superconducting properties.

Contribution

It provides the first microscopic evidence of phase separation and detailed magnetic fluctuation behavior in Ba1-xKxFe2As2 using 75As NMR.

Findings

Microscopic separation of magnetic and superconducting phases.

Presence of large two-dimensional antiferromagnetic spin fluctuations.

Superconducting state shows a T^3 dependence of 1/T1 with no coherence peak.

Abstract

We report the 75As nuclear magnetic resonance (NMR) measurement of the hole-doped superconductor Ba1-xKxFe2As2 with different lattice parameters and different superconducting volume fractions (Tc = 38K). 75As-NMR spectra revealed that the magnetically ordered and superconducting phases are microscopically separated. The spin-lattice relaxation rate 1/T1 in the normal state reflects the existence of a large two-dimensional antiferromagnetic spin fluctuation. The 1/T1 in the superconducting state down to the lowest measurement temperature T varies close to T^3. In addition, it exhibits no coherence peak just below Tc. This shows a T dependence similar to those of other iron pnictides.