biostudies-literatureUnknown118(17)Markov MCombining ferroelectricity with other properties such as visible light absorption or long-range magnetic order requires the discovery of new families of ferroelectric materials. Here, through the analysis of a high-throughput database of phonon band structures, we identify a structural family of anti-Ruddlesden-Popper phases [Formula: see text]O (A=Ca, Sr, Ba, Eu, X=Sb, P, As, Bi) showing ferroelectric and antiferroelectric behaviors. The discovered ferroelectrics belong to the new class of hyperferroelectrics that polarize even under open-circuit boundary conditions. The polar distortion involves the movement of O anions against apical A cations and is driven by geometric effects resulting from internal chemical strains. Within this structural family, we show that [Formula: see text]O combines coupled ferromagnetic and ferroelectric order at the same atomic site, a very rare occurrence in materials physics.Proceedings of the National Academy of Sciences of the United States of Americae2026020118https://www.ebi.ac.uk/biostudies/studies/S-EPMC8092399biostudies-literatureFerroelectricity and multiferroicity in anti-Ruddlesden-Popper structures.PMC8092399Petretto GGeorge JGhosez PMarkov MMiranda HPCBousquet EHautier GChen WRignanese GMAlaerts LfalseFerroelectricity and multiferroicity in anti-Ruddlesden-Popper structures.Combining ferroelectricity with other properties such as visible light absorption or long-range magnetic order requires the discovery of new families of ferroelectric materials. Here, through the analysis of a high-throughput database of phonon band structures, we identify a structural family of anti-Ruddlesden-Popper phases [Formula: see text]O (A=Ca, Sr, Ba, Eu, X=Sb, P, As, Bi) showing ferroelectric and antiferroelectric behaviors. The discovered ferroelectrics belong to the new class of hyperferroelectrics that polarize even under open-circuit boundary conditions. The polar distortion involves the movement of O anions against apical A cations and is driven by geometric effects resulting from internal chemical strains. Within this structural family, we show that [Formula: see text]O combines coupled ferromagnetic and ferroelectric order at the same atomic site, a very rare occurrence in materials physics.2021-01-01T00:00:00Z2021 Apr2025-04-26T23:50:45.092Z2025-04-06T17:38:54.365ZS-EPMC80923993389323810.1073/pnas.2026020118