Scientists believe they’ve made a concrete example of an unusual, theoretical form of ferromagnetism first described by a researcher more than 50 years ago.

Nagaoka ferromagnetism, named for the scientist who discovered it, Yosuke Nagaoka, is a special case of the same magnetic forces that make regular, refrigerator-type magnets work—ferro meaning iron, plus a few other metals that are naturally receptive to magnetism. Identifying it in real life—in this case using a quantum system of electrons—can help scientists understand how spontaneous ferromagnetism works.