Anisotropic atomic displacements, local orthorhombicity and anomalous local magnetic moment in Ba0.6K0.4Fe2As2 superconductor

• Published in: Physical chemistry chemical physics : PCCP 2024-08, Vol.26 (34), p.22454-22462
• Main Authors: Tortora, L, Tomassucci, G, Pugliese, G M, Hacisalihoglu, M Y, Simonelli, L, Marini, C, Das, G, Ishida, S, Iyo, A, Eisaki, H, Mizokawa, T, Saini, N L
• Format: Article
• Language: English
• Subjects: Anisotropy; Atomic structure; Chemical bonds; Electronic structure; Emission spectra; Fine structure; Iron; Magnetic moments; Transition temperature; X ray absorption
• ISSN: 1463-9076; 1463-9084; 1463-9084
• DOI: 10.1039/d4cp02345e

We have investigated the in-plane local structure of the Ba0.6K0.4Fe2As2 superconductor by polarized Fe K-edge extended X-ray absorption fine structure (EXAFS) measurements with temperature. The near neighbor bond distances and their stiffness, measured by polarized EXAFS in two orthogonal directions, are different suggesting in-plane anisotropy of the atomic displacements and local orthorhombicity in the title system. The X-ray absorption near edge structure (XANES) spectra reveal anisotropy of valence electronic structure that changes anomalously below ∼100 K. The local iron magnetic moment, measured by Fe Kβ X-ray emission spectroscopy (XES), increases below the anomalous temperature and shows a decrease in the vicinity of the superconducting transition temperature (Tc ∼ 36 K). The results provide a clear evidence of coupled local lattice, electronic and magnetic degrees of freedom to induce possible nematic fluctuations in an optimally hole doped iron-based superconductor.