Ferromagnetism above 1000 K in a highly cation-ordered double-perovskite insulator Sr<sub>3</sub>OsO<sub>6</sub>.

Wakabayashi, Yuki K; Krockenberger, Yoshiharu; Tsujimoto, Naoto; Boykin, Tommy; Tsuneyuki, Shinji; Taniyasu, Yoshitaka; Yamamoto, Hideki · Nat Commun · 2019

basic_science · Level V

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Abstract

Magnetic insulators have wide-ranging applications, including microwave devices, permanent magnets and future spintronic devices. However, the record Curie temperature (TC), which determines the temperature range in which any ferri/ferromagnetic system remains stable, has stood still for over eight decades. Here we report that a highly B-site ordered cubic double-perovskite insulator, Sr3OsO6, has the highest TC (of ~1060 K) among all insulators and oxides; also, this is the highest magnetic ordering temperature in any compound without 3d transition elements. The cubic B-site ordering is confirmed by atomic-resolution scanning transmission electron microscopy. The electronic structure calculations elucidate a ferromagnetic insulating state with Jeff = 3/2 driven by the large spin-orbit coupling of Os6+ 5d2 orbitals. Moreover, the Sr3OsO6 films are epitaxially grown on SrTiO3 substrates, suggesting that they are compatible with device fabrication processes and thus promising for spintronic applications.