  Cavity spintronics recently heralded non-local magnonic signal transfer
between magnetic samples. Here we show that by including superconductors in the
cavity, we can make use of these principles to bring composite
superconductor--ferromagnet systems to the macroscale. We analyze how a
superconductor's a.c. conductivity influences the spin dynamics of a spatially
separated magnet, and we discuss the potential impact on spintronic
applications.
