Two-Dimensional Short-Range Chemical Ordering in Ba1-xNaxFe2As2
Abstract
A true understanding of the properties of pnictide superconductors require the development of high-quality materials and performing measurements designed to unravel their intrinsic properties and short-range nematic correlations which are often obscured by extrinsic effects such as poor crystallinity, inhomogeneity, domain formation and twinning. In this paper, we report the systematic growth of high-quality Na-substituted BaFe2As2 single crystals and their characterization using pulsed-magnetic fields x-ray diffraction and x-ray diffuse scattering. Analysis of the properties and compositions of the highest quality crystals show that their actual Na stoichiometry is about 50-60% of the nominal content and that the targeted production of crystals with specific compositions is accessible. We derived a reliable equation to estimate the Na stoichiometry based on the measured superconducting TC of these materials. Attempting to force spin reorientation and induce tetragonality, orthorhombic Ba1-xNaxFe2As2 single crystals subjected to out-of-plane magnetic fields up to 31.4T are found to exhibit strong in-plane magnetic anisotropy demonstrated by the insufficiency of such high fields in manipulating the relative population of their twinned domains or in suppressing the orthorhombic order. Broad x-ray diffuse intensity rods observed at temperatures between 30 K and 300 K uncover short-range structural correlations. Local structure modeling together with 3D-{\Delta}PDF mapping of real-space interatomic vectors show that the diffuse scattering arises from in-plane short-range chemical correlations of the Ba and Na atoms coupled with short-range atomic displacements within the same plane due to an effective size difference between the two atomic species.
Cite
@article{arxiv.2304.07960,
title = {Two-Dimensional Short-Range Chemical Ordering in Ba1-xNaxFe2As2},
author = {R. Stadel and R. DeRose and K. M. Taddei and M. J. Krogstad and P. Upreti and Z. Islam and D. Phelan and D. Y. Chung and R. Osborn and S. Rosenkranz and O. Chmaissem},
journal= {arXiv preprint arXiv:2304.07960},
year = {2023}
}