For thousands of years, people have been drawn to the apparent magic of magnets. Ancient Greek philosophers believed dark rocks called lodestones had souls because of their ability to move iron flakes.

Physicists now know that magnetic materials glean their power from the behavior of the atoms inside them. But magnetism still holds secrets. Researchers have recently found signs of a wholly new class of magnetism, one with characteristics of each of the two conventional kinds, ferromagnetism and antiferromagnetism.