Not yet reviewed by Pith; the record is open.

It is proposed a novel method of the spectrally selective detection of the short spin waves (or magnons) by means of the transverse magneto-optical (MO) intensity effect in transmission in the magnetoplasmonic nanostructure. The method is based on the analysis of the MO effect spectrum versus the modulation of the sample magnetization (i.e. spin wave) and related spatial symmetry breaking in the magnetic layer. The spatial symmetry breaking leads to the appearance of MO effect modulation at the normal incidence of light in the spectral range of the optical states (SPP and waveguide modes) and the breaking of the antisymmetry of the effect with respect to the sign of the incidence angle of light. Besides it is revealed that the magnitude of the MO effect varies with respect to the phase shift between the spin wave and the plasmonic grating as a harmonic function with a period equal to the magnon wavelength. All these facts allow to detect the spin waves of the certain wavelength propagating in the nanostructure by measuring of the MO effect in the nanostructure.