paper

Ferro-octupolar order and low-energy excitations in d double perovskites of Osmium

arXiv:2107.04493 · doi:10.1103/PhysRevLett.127.237201

Abstract

Conflicting interpretations of experimental data preclude the understanding of the quantum magnetic state of spin-orbit coupled double perovskites. Whether the ground state is a Janh-Teller-distorted order of quadrupoles or the hitherto elusive octupolar order remains debated. We resolve this uncertainty through direct calculations of all-rank inter-site exchange interactions and inelastic neutron scattering cross-section for the double perovskite series BaOsO (= Ca, Mg, Zn). Using advanced many-body first principles methods we show that the ground state is formed by ferro-ordered octupoles coupled by superexchange interactions within the ground-state doublet. Computed ordering temperature of the single second-order phase-transition is consistent with experimentally observed material-dependent trends. Minuscule distortions of the parent cubic structure are shown to qualitatively modify the structure of gaped magnetic excitations.

6 pages + 12 pages of Supplementary. Final published version

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