Giant spin-accumulation signal and pure spin-current-induced reversible magnetization switching

Abstract

A key element in spintronics is the spin-transfer effect, by which the magnetization in a nanomagnet can be switched. The effect has already been demonstrated using spin-polarized electrical currents, but now reversible magnetization switching has been achieved using a pure, chargeless spin current. A number of proposed next-generation electronic devices, including novel memory elements1 and versatile transistor circuits2, rely on spin currents, that is, the flow of electron angular momentum. A spin current may interact with a magnetic nanostructure and give rise to spin-dependent transport phenomena, or excite magnetization dynamics1,2,3,4,5,6,7,8,9,10,11. In contrast to a spin-polarized charge current, a pure spin current does not produce any charge-related spurious effects12,13. One way to produce a pure spin current is non-local electrical-spin injection12,13,14,15,16,17,18, but this approach has suffered so far from low injection efficiency. Here, we demonstrate a significant enhancement of the non-local injection efficiency in a lateral spin valve prepared with an entirely in situ fabrication process. Improvements to the interface quality and the device structure lead to an increase of the spin-signal amplitude by an order of magnitude. The generated pure spin current enables the magnetization reversal of a nanomagnet with the same efficiency as in the case of using charge currents. These results are important for further theoretical developments in multi-terminal structures2, but also with a view towards realizing novel devices driven by pure spin currents.