Yiu-Fung Chiu

If you hold an iron nail near a magnet, it will be attracted. Inside the magnet, tiny atomic magnetic arrows point in the same direction, like soldiers in formation. But in some crystals, the formation is different: neighboring arrows point in opposite directions. This order is called altermagnetism, and it is hard to see directly.

The magnetic framework of the EuMnSb2 crystal resembles scaffolding: manganese atoms form rigid vertical pillars, while europium atoms act as movable crossbars. Until now, there was no consensus on the angle at which these crossbars rest and how they rotate when a magnetic field presses on the scaffold.