Optimization of the Parameters of a Ferromagnet/Tunnel Barrier/Noncollinear Ferromagnet System for the Generation of Electromagnetic Radiation

The possibility for the generation of electromagnetic radiation due to the transition of conduction electrons between spin subbands of a noncollinear ferromagnet in a ferromagnet/tunnel barrier/noncollinear ferromagnet system has been studied. In such a system, the injection of a nonequilibrium spin into a noncollinear ferromagnet is due to an electric current polarized in spin by the first homogeneous ferromagnet. It is shown that in the case as both the ferromagnets are “bad” metals or semiconductors, the critical generation current can substantially decrease as compared to the case as the ferromagnets are “good” metals. The obtained estimations for the critical current can be realized experimentally. The frequency of electromagnetic wave radiated by this system can be controlled by applying various voltages to the system.