spinpumping

Spin pumping is a phenomenon in condensed matter physics where a time-varying magnetization in one material generates a flow of angular momentum, or spin current, into an adjacent material. This typically occurs when a ferromagnetic material is excited to precess its magnetization, for example, by applying an alternating magnetic field or through microwave excitation. The precessing magnetization acts like a collective motion of spins, and this motion can impart angular momentum to the spins in a nearby non-magnetic material, often a metal.

The generated spin current is a flow of spins rather than a flow of charge. This means that while there is a transfer of angular momentum, there is no net electrical current. The interface between the two materials is crucial for efficient spin pumping. The interaction at this interface allows the angular momentum to be transferred from the precessing spins in the ferromagnet to the conduction electrons or other spin carriers in the adjacent material.

Spin pumping is a key mechanism for generating and detecting spin currents. It has important implications for spintronic devices, which aim to utilize the spin of electrons in addition to their charge for information processing and storage. For instance, spin pumping can be used to excite spin waves in magnetic insulators or to drive spin-dependent transport phenomena in metallic layers. The efficiency of spin pumping depends on factors such as the magnetic properties of the ferromagnetic material, the nature of the interface, and the spin-transport properties of the adjacent material.