Magnetoelastic coupling and charge correlation lengths in a twin domain of Ba(Fe1−xCox)2As2 (x=0.047): A high-resolution x-ray diffraction study

The interplay between structure, magnetism, and superconductivity in single crystal Ba(Fe1−xCox)2As2 (x=0.047) has been studied using high-resolution x-ray diffraction by monitoring charge Bragg reflections in each twin domain separately. The emergence of the superconducting state is correlated with the suppression of the orthorhombic distortion around TC, exhibiting competition between orthorhombicity and superconductivity. Above TS, the in-plane charge correlation length increases with the decrease of temperature, possibly induced by nematic fluctuations in the paramagnetic tetragonal phase. Upon cooling, anomalies in the in-plane charge correlation lengths along a (ξa) and baxes (ξb) are observed at TS and also at TN indicative of strong magnetoelastic coupling. The in-plane charge correlation lengths are found to exhibit anisotropic behavior along and perpendicular to the in-plane component of stripe-type AFM wave vector (101)O below around TN. The temperature dependence of the out-of-plane charge correlation length shows a single anomaly at TN, reflecting the connection between Fe-As distance and Fe local moment. The origin of the anisotropic in-plane charge correlation lengths ξa and ξb is discussed on the basis of the antiphase magnetic domains and their dynamic fluctuations