Altermagnets: The Hidden Dance of Spins express
Altermagnets resemble a ballroom where couples spin in opposite directions: the hall itself is still, but inside, ordered motion seethes. Similarly, electron spins (the direction of their rotation) in these materials form intricate patterns without creating an overall magnetism. This hidden "choreography" allows electrons with different spins to move in opposite directions, like dancers spreading out to the edges of the floor. This effect separates charge carriers without an external magnet.
Physicists have proposed a theoretical description for achiral altermagnets, where spins not only point up or down but twist into three-dimensional figures that are symmetric under reflection. The model, rooted in the work of Lev Landau and relying on conventional particle physics, predicts an enhancement of spin current and piezomagnetism — the ability to slightly magnetize when compressed, as if pressing on the dance floor causes some couples to move in sync.
An experiment with NiS2 crystal showed that upon cooling, internal disorder decreases and spins align into two successive structures. Light-based analysis confirmed that the unconventional geometry makes the order remarkably robust — tougher than in simple altermagnets. This opens the way to spintronic devices, where information is carried by spin direction, promising faster and more energy-efficient electronics.
Altermagnetism was theoretically predicted only in 2019, but over a hundred materials with such properties have already been found, including NiS2.
Controlling spins without magnetic fields transports us to a sci-fi world where 'spin computers' operate without energy consumption, like in novels about the far future.