In magnetic memory devices, information is stored in magnetic elements and typically retrieved by applying a small, external magnetic field. More convenient, however, is the use of a spin-polarized current, in which moving electrons exert a torque on a magnetic element and can switch the direction of its magnetization.
Unfortunately, moving electrons can give rise to electrical noise, which reduces the efficiency of the magnetization control. Now, Yoshichika Otani from the RIKEN Advanced Science Institute in Wako and colleagues have overcome this problem by using a pure spin current*, that is, a diffusion of electron spins without charge motion.
By examining the electronic transport properties of their device, the researchers were able to demonstrate that when the current injected into the first junction is high enough, it creates a spin current high enough to reverse the magnetization at the second junction. Most importantly, the magnetization can be reversed back by applying the same amount of current in the opposite direction.