Exchange-Induced Generation of Electromagnetic Radiation in a Helical Magnetic Structure

Emission of electromagnetic radiation due to spin-flip transitions in a ferromagnet

“…Our estimations of critical current and R st in the previous subsection were performed for the stationary non-equilibrium state (31) that does not take into account the electromagnetic wave emission. For small deviations of δ N from δ N * determined by (31) we may suppose linear dependence of R st on δ N (this is confirmed by the results of previous work for relatively small current [28]). Using equation (24) we may suppose…”

“…This corresponds to previously used equation for spin-polarized electron density [20,21,28] where η was introduced phenomenologically. It should be noted that the spin injection efficiency is determined by both the exchange constant of spin source J s and the exchange constant of active region J.…”

“…In the existing literature [20,21,23,28] it is implied that all injected electrons immediately relax to the lowest vacant states inside the spin subband, thus supposing that the energy relaxation time τ e << τ s and besides τ e << L v F . However typical time of electron pass through the active region L v F is much smaller than τ e for the thickness of the active region L ∼ 10nm (the electromagnetic wave emission is accompanied by the change of electron energy but these processes are supposed to give a small correction to τ e ) [43].…”

“…Finally, a fully exchange mechanism exists in non-collinearly magnetized ferromagnets due to the connection between spin and spatial coordinates in such ferromagnets. This mechanism was theoretically demonstrated recently [28] and is studied insufficiently. We consider the magnetic helicoid (Bloch type spiral):…”

Study of reflection and transmission spectra of arrays of heterogeneous ferromagnetic nanowires in the terahertz and far infrared ranges

“…However, with homogeneous magnetization of the ferromagnetic medium, the matrix element for the spin-flip transition operator turns out to be zero [30]. Therefore, to implement the mentioned mechanism of interaction of electrons with THz radiation, either the exchange interaction constant must be a tensor in spin indices [30], or the magnetization of the medium must be heterogeneous [31]. In the second case, the spin parts of the wave functions of the conduction electrons have a more complex form than with homogeneous magnetization of the medium, which leads to the fact that the matrix element of the spin-flip transition is not zero.…”