Regensburg 2022 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 7: Microstructures and Phase Transformations: Oxides & Perovskites

MM 7.4: Talk

Monday, September 5, 2022, 16:30–16:45, H45

Hidden charge order in square-lattice Sr₃Fe₂O₇ — •Darren C. Peets^1,2,3, Jung-Hwa Kim¹, Manfred Reehuis⁴, Peter Adler⁵, Andrey Maljuk^1,6, Tobias Ritschel², Morgan C. Allison², Jochen Geck^2,7, Jose R. L. Mardegan⁸, Pablo J. Bereciartua Perez⁸, Sonia Francoual⁸, Andrew C. Walters^1,9, Thomas Keller^1,10, Paula M. Abdala¹¹, Philip Pattison^11,12, Pinder Dosanjh¹³, and Bernhard Keimer¹ — ¹MPI-FKF, 70569 Stuttgart — ²IFMP, TU Dresden, 01069 Dresden — ³NIMTE CAS, Ningbo, 315201 China — ⁴HZB, 14109 Berlin — ⁵MPI-CPfS, 01187 Dresden — ⁶IFW, 01171 Dresden — ⁷ct.qmat, TU Dresden, 01062 Dresden — ⁸DESY, Hamburg 22603 — ⁹Diamond, Didcot OX11 0DE, UK — ¹⁰MPI Outstation at MLZ, 85748 Garching — ¹¹SNBL at ESRF, 38042 Grenoble, France — ¹²EPFL, BSP-Dorigny, CH-1015 Lausanne, Switzerland — ¹³UBC, Vancouver, V6T 1Z1 Canada

Since the discovery of charge disproportionation in Sr₃Fe₂O₇ by Mössbauer spectroscopy >50 years ago, the spatial ordering pattern of the disproportionated charges has stayed “hidden” to conventional diffraction, despite numerous x-ray and neutron studies. Our neutron Larmor diffraction and Fe K-edge resonant x-ray scattering demonstrate checkerboard charge order in the FeO₂ planes that vanishes at a sharp second-order phase transition at 332 K. Stacking disorder of the checkerboard pattern due to frustrated interlayer interactions broadens their superstructure reflections, greatly reducing their amplitude, explaining the difficulty to detect them. We discuss implications of these findings for research on “hidden order” in other materials.