Paul Steffens

Drop a stone into a pond, and ripples spread across the water. Magnets have waves too — only instead of water molecules, it's the directions of atomic magnetic arrows that oscillate. These waves are called magnons, and their behavior reveals a lot about the invisible forces between atoms.

The hanmilite crystal, resembling a layered cake of copper and boron, behaves like a ladder: the copper spins are arranged in two parallel rails connected by rungs.