A switch to control the spin current
https://phys.org/news/2018-05-current.html
Spintronics is an emerging field of nanoscale electronics which uses not only the charge of electrons but also the spin of electrons. The technology doesn't require a specialized semiconductor material resulting in reduced manufacturing costs.
Other advantages include less energy requirement, as well as low power consumption with competitive data transfer and storage capacity. It has been used in a variety of devices for information processing, memory and storage—in particular, ultra-high density hard drives and non-volatile memories.