Since the discovery of charge disproportionation in the FeO2 square-lattice compound Sr3Fe2O7 by M\"ossbauer spectroscopy more than fifty years ago, the spatial ordering pattern of the disproportionated charges has remained "hidden" to conventional diffraction probes, despite numerous x-ray and neutron scattering studies. We have used neutron Larmor diffraction and Fe K-edge resonant x-ray scattering to demonstrate checkerboard charge order in the FeO2 planes that vanishes at a sharp second-order phase transition upon heating above 332 K. Stacking disorder of the checkerboard pattern due to frustrated interlayer interactions broadens the corresponding superstructure reflections and greatly reduces their amplitude, thus explaining the difficulty to detect them by conventional probes. We discuss implications of these findings for research on "hidden order" in other materials.
@article{arxiv.2108.02527,
title = {Hidden Charge Order in an Iron Oxide Square-Lattice Compound},
author = {Jung-Hwa Kim and Darren C. Peets and Manfred Reehuis and Peter Adler and Andrey Maljuk and Tobias Ritschel and Morgan C. Allison and Jochen Geck and Jose R. L. Mardegan and Pablo J. Bereciartua Perez and Sonia Francoual and Andrew C. Walters and Thomas Keller and Paula M. Abdala and Philip Pattison and Pinder Dosanjh and Bernhard Keimer},
journal= {arXiv preprint arXiv:2108.02527},
year = {2021}
}
Comments
PRL in press, 12 pages including Supplementary, CIF files available as ancillary files