Dongsheng Song

A ruthenium oxide film is like a soap bubble film stretched over a frame, but made of atoms. For a long time, it was believed that in this film, ruthenium atoms align in a magnetic order, like compass needles pointing in opposite directions. This order was dubbed altermagnetism, and great hopes were placed on it for future electronics.

Inside a piece of magnetic material, electron spins, tiny magnetic arrows, usually arrange into simple patterns. Sometimes they swirl into vortices, like water down a drain, and these vortices can tie themselves into knots.