Emission of coherent spin waves from a helimagnetic layer embedded within a ferromagnetic matrix

We have studied the Schlömann emission of exchange spin waves by a microwave driven helimagnetic layer containing integer and half-integer numbers of turns into surrounding semi-infinite ferromagnetic media. Analytical expressions of the emitted spin-wave’s amplitude and phase are obtained in closed form. For the case of a half-integer number of turns, we propose a method for applying the driving magnetic field so that the emission has an asymmetric (nonreciprocal) character, controlled by the polarization of the driving magnetic field. Our results can be used both in the design of polarization-sensitive magnonic detectors of microwaves and in using microwaves to characterize the microscopic configuration of non-collinear magnetic materials.