Magnetoelastic coupling and charge correlation lengths in a twin domain of Ba(Fe1â‹TMxCox)2As2 (x=0.047): A high-resolution x-ray diffraction study

The interplay between structure, magnetism, and superconductivity in single crystal Ba(Fe 1−x Co x) 2 As 2 (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 T C , exhibiting competition between orthorhombicity and superconductivity. Above T S , 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 (ξ a) and b axes (ξ b) are observed at T S and also at T N 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 T N. The temperature dependence of the out-of-plane charge correlation length shows a single anomaly at T N , reflecting the connection between Fe-As distance and Fe local moment. The origin of the anisotropic in-plane charge correlation lengths ξ a and ξ b is discussed on the basis of the antiphase magnetic domains and their dynamic fluctuations.