The orientation of spins can be readily controlled by externally applied magnetic fields. This has been the foundation of magnetic technologies ranging from the compass to magnetic recording. The magnetic fields in present-day devices are typically generated from electrical currents. The properties of such Oersted fields are given by the electrical circuit and independent of the properties of the magnetic moments which they control.
We explore the physical foundations of controlling spins without such Oersted fields. We rather explore the coupling of solid-state spins to their environment to generate torques from quantum mechanical exchange- and spin-orbit-coupling phenomena. This enables control and read-out of dynamical spin phenomena by electrons, phonons, photons and magnons as depicted in the figure.
These hybrid spin-control schemes enable the manipulation of magnetic systems with unique properties and efficiencies that cannot be achieved with Oersted fields. A good understanding of the underlying interaction phenomena is crucial to bring these schemes into the realm of practical applications, which are in particular found in spin-based computation and data storage.