Research: Hidden Charge Order in an Iron Oxide Square-Lattice Compound

An international team of researchers, including projects C03 and C06 of SFB 1143, has resolved the origin of a mysterious phase transition in the layered perovskite Sr₃Fe₂O₇ around room temperature. Although first evidence for the onset of electronic order at this transition upon cooling has been reported more than fifty years ago, all attempts to elucidate the microscopic structure of that order failed. In the present study, the researchers employed cutting-edge neutron and X-ray diffraction methods to search for this "hidden order". The breakthrough was finally achieved by means resonant X-ray diffraction, which enabled to detect the spontaneous formation of a checkerboard-type electronic order.

J.-H. Kim, D. C. Peets, M. Reehuis, P. Adler, A. Maljuk, T. Ritschel, M. C. Allison, J. Geck, J. R. L. Mardegan, P. J. Bereciartua Perez, S. Francoual, A. C. Walters, T. Keller, P. M. Abdala, P. Pattison, P. Dosanjh, B. Keimer,
Hidden Charge Order in an Iron Oxide Square-Lattice Compound,
Phys. Rev. Lett. 127, 097203 (2021)