Ferromagnetic insulators are uncommon

Magnetic interactions in oxides have been extensively studied by John B. Goodenough, one of the three recipients of the 2019 Nobel Prize in Chemistry. His models of direct and indirect exchange interactions form part of the foundation of our own R&D, as demonstrated in our publication in Annalen der Physik.

As emphasized by P. W. Anderson in his classic paper New approach to the theory of superexchange interactions, Phys. Rev. 115, 2–13 (1959), the dominant coupling between magnetic cations in most oxides is antiferromagnetic — even in many ferrimagnetic materials. This is why true ferromagnetic insulators are rare, and room‑temperature ferromagnetic insulators are exceptionally uncommon. As a result, experiments requiring insulating ferromagnets are typically performed at cryogenic temperatures using specialized, high‑cost instrumentation.

Room‑temperature insulating ferromagnets enable new device concepts

The importance of understanding magnetic and disordered systems was recognized by the 1977 Nobel Prize in Physics, awarded to Philip W. Anderson, Sir Nevill F. Mott, and John H. van Vleck for their fundamental theoretical contributions. Their work continues to guide the development of new magnetic materials and device architectures.

Room‑temperature insulating ferromagnets open the door to practical implementations of concepts that previously required cryogenic environments. These materials enable low‑loss spin‑wave propagation, tunable magnetic behavior, and new approaches to information processing, RF components, and hybrid photonic–electronic systems.