Dresden 2026 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 31: Frustrated Magnets I (joint session MA/TT)

TT 31.2: Talk

Tuesday, March 10, 2026, 09:45–10:00, POT/0361

Antiferro octupolar order in the 5d¹ double perovskite Sr₂MgReO₆ and its spectroscopic signatures — •Dario Fiore Mosca¹ and Leonid Pourovskii^2,3 — ¹University of Vienna, Faculty of Physics and Center for Computational Materials Science, Vienna, Austria — ²CPHT, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, 91120 Palaiseau, France — ³College de France, Université PSL, 11 place Marcelin Berthelot, 75005 Paris, France

Hidden-order phases governed by high-rank multipolar order parameters have recently been identified in several cubic 5d double perovskites. Because experimental probes often couple weakly to high-rank moments, multipolar orders can remain elusive or be misinterpreted as lower-rank phases. A notable example is the 5d¹ double perovskite Sr₂MgReO₆, originally proposed as a spin glass and later reclassified as a conventional dipolar antiferromagnet.

In this work, we show instead that Sr₂MgReO₆ hosts a hidden antiferroic order of magnetic octupoles. The dominant tetragonal crystal field isolates a doublet carrying octupolar degrees of freedom, while weak dipolar moments arise only through admixture of the excited j = 1/2 spin-orbit multiplet. This octupolar order produces characteristic quasigapless magnetic excitations and superstructural neutron-diffraction intensities that peak at large scattering momenta.

This results highlights the tunability of multipolar interactions in spin-orbit entangled materials and places Sr₂MgReO₆ with unconventional octupolar phases.

Keywords: Hidden Orders; Multipolar interactions; Spin-orbit coupling; Double perovskites; Multipolar order