Combinatorics

Physics

Nanotechnology

Magnetization

Mathematics

Crystallography

Ferromagnetism

Magnetic field

Epitaxy

Perovskite (structure)

Spintronics

Chemistry

Metallurgy

Materials science

Condensed matter physics

Layer (electronics)

Oxide

Quantum mechanics

Curie temperature

Saturation (graph theory)

Advanced Materials

Ferromagnetic insulators (FMIs) are one of the most important components in developing dissipationless electronic and spintronic devices. However, since ferromagnetism generally accompanies metallicity, FMIs are innately rare to find in nature. Here, novel room-temperature FMI films are epitaxially synthesized by deliberate control of the ratio of two B-site cations in the double perovskite Sr2FeReO6. In contrast to the known ferromagnetic metallic phase in stoichiometric Sr2FeReO6, a FMI state with a high Curie temperature (Tc~400 K) and a large saturation magnetization (MS~1.8 {\mu}B/f.u.) is found in highly cation-ordered Fe-rich phases. The stabilization of the FMI state is attributed to the formation of extra Fe3+-Fe3+ and Fe3+-Re6+ bonding states, which originate from the excess Fe. The emerging FMI state by controlling cations in the epitaxial oxide perovskites opens the door to developing novel oxide quantum materials & heterostructures.

Room‐Temperature Ferromagnetic Insulating State in Cation‐Ordered Double‐Perovskite Sr2Fe1+xRe1−xO6Films