Magnetic Order on Command

In 1996, Luc Berger and John Slonczewski [1] conceived of a way to use an electrical current to reverse the magnetization of a thin metal film. The trick was to apply a current of electrons whose spins were aligned in the same direction: Upon passing through the film, this “spin current” would exert a large enough torque on the film’s magnetization to flip it around. Experimentalists soon demonstrated the predicted switching effect [2], which led, among other things, to racetrack memories—devices that use a spin current to move and position information encoded in tiny magnetic domains [3]. Seokhwan Choi of the Korea Advanced Institute of Science and Technology and co-workers have now uncovered a new type of spin-current switching effect, this time in an iron-based superconductor [4]. The researchers show that the current can be used to modify two phenomena—magnetism and superconductivity—that coexist in the material. The effect could, like the one Berger and Slonczewski predicted, lead to new types of devices and experiments.