Generating Spin Current with Heat
For decades we have been using electronics that operate on the charge of electrons, and while the technology has been serving us very well, it is approaching its limits. A potential replacement is spintronics, which utilize another property of electrons known as spin and spin current. Among the many benefits of spintronics is the possibility of great speed, and now researchers at the University of Illinois have found a way to create spin currents at that great speed.
A normal electrical current, like those used in electronics, is made of electrons with spins pointing in random directions. A spin current is formed when those spins line up, but causing that to happen is not easy. Normally it requires creating a voltage difference across a structure, but the Illinois researchers were able to produce a current using heat instead. Within a metallic ferromagnet are three energy reservoirs, and by creating a temperature difference between two of them, the researchers were able to generate a spin current. The two reservoirs are electrons and magnons, and the temperature difference caused the spin angular momentum of the magnons to be transported to the electrons.
Unlike the more traditional means of producing a spin current, this thermally-driven method created the current in trillionths of a second, or picoseconds. Naturally this great speed would be very welcome for fast magnetic memory devices.
Source: University of Illinois