  The use of spin waves as a signal carrier requires developing the functional
elements allowing for multiplexing and demultiplexing information coded at
different wavelengths. For this purpose, we propose a system of thin
ferromagnetic layers dynamically coupled by a rectangular ferromagnetic
resonator. We show that a single and double, clockwise and counter-clockwise,
circulating modes of the resonator offer a wide possibility of control of
propagating waves. Particularly, at frequency related to the double-clockwise
circulating spin-wave mode of the resonator, the spin wave excited in one layer
is transferred to the second one where it propagates in the backward direction.
Interestingly, the wave excited in the second layer propagates in the forward
direction only in that layer. This demonstrates add-drop filtering, as well as
circulator functionality. Thus, the proposed system can become an important
part of future magnonic technology for signal routing.
