  A systematic study of the coupling at room temperature between ferromagnetic
resonance (FMR) and a planar resonator is presented. The chosen magnetic
material is a ferrimagnetic insulator (Yttrium Iron Garnet: YIG) which is
positioned on top of a stop band (notch) filter based on a stub line
capacitively coupled to a 50 $\Omega$ microstrip line resonating at 4.731 GHz.
Control of the magnon-photon coupling strength is discussed in terms of the
microwave excitation configuration and the YIG thickness from 0.2 to 41 $\mu$m.
From the latter dependence, we extract a single spin-photon coupling of
g$_{0}$/2$\pi$=162$\pm$6 mHz and a maximum of an effective coupling of 290 MHz.
