Researchers at the University of Basel and ETH Zurich have found a way to flip the magnetic polarity of an unusual ferromagnet using a laser beam. If the approach can be refined and scaled, it points toward electronic components that could be reconfigured with light instead of being permanently fixed.
A ferromagnet acts like it has a built-in internal agreement. Inside the material, enormous numbers of electrons behave like tiny bar magnets because of their spins. When those spins line up, their individual magnetic fields add together, producing the familiar strength that makes a compass needle settle in a direction or lets a refrigerator magnet cling to a door.
That orderly alignment is not automatic, because heat constantly shakes the system. Ferromagnetism appears only when the interactions that encourage alignment win out over thermal motion, which happens below a critical temperature (often called the Curie temperature).









