New microwave nonreciprocal properties are investigated in “ferrite plate
– grating of resonant elements” metasandwiches arranged along the axis of
a rectangular waveguide in a transverse constant magnetic field. Giant
nonreciprocity in the transmission is observed at the ferromagnetic
resonance frequencies at certain values of the magnetic field under
conditions of a mutual influence between the ferromagnetic and the grating
resonances. In addition, nonreciprocal splitting of the resonance in grating
elements is observed under small magnetic field, which is much less than the
field necessary to the ferromagnetic resonance excitation.
The nonreciprocal transmission does not take place in the case of free
ferrite in the absence of a grating. Sign reversal of the nonreciprocity is
observed, when ferrite transfers to the opposite side of a grating as well
as under certain values of the constant magnetic field, when the sign
reversal of difference between frequencies of the ferromagnetic resonance
and the grating resonance takes place. Nonreciprocal effects are explained
by the interaction between precessing spins in ferrite and a magnetic field
of the surface wave, formed by a grating, and by coupling between the
resonances of grating elements. It has been shown theoretically that
microwaves in waveguide with bianisotropic layer, simulating a grating of
resonant elements, are elliptically or circularly polarized with frequency
and spatially – dependent rotating sense of the microwave magnetic field.
The nonreciprocal effects have been observed for different grating elements:
for both electric dipoles and chiral elements.