Magnons driven by spin-transfer torque: basics and applications

The emerging field of nano-magnonics takes advantage of high-frequency waves of magnetization – spin waves/magnons – for the transmission and processing of information on the nanoscale. The advent of spin-transfer torque, resulting from the exchange of angular momentum from conducting electrons to magnetic subsystem, has spurred significant advances in nano-magnonics, by enabling highly efficient local spin-wave generation in magnonic nano-devices. Furthermore, the recent advances of spin-orbitronics has provided a unique ability to exert spin-transfer torque over spatially extended areas of magnonic structures, based on both metallic and insulating magnetic films.

 

In the first part of my talk I will analyze magnons driven by the spin-transfer torque from the thermodynamic point of view and will show that they form a quasi-equilibrium gas described by the Bose-Einstein statistics with a non-zero chemical potential, suggesting the possibility of electrically-driven Bose-Einstein condensation of magnons.

 

In the second part, I will address different nano-magnonic devices allowing, among others, controllable directional asymmetry of spin wave emission, which is highly beneficial for applications in non-reciprocal spin-wave logics and neuromorphic computing.