We implement superconducting Yttrium barium copper oxide planar resonators with two
fundamental modes for circuit quantum electrodynamics experiments. We first demonstrate
good tunability in the resonant microwave frequencies and in their interplay, as emerges
from the dependence of the transmission spectra on the device geometry. We then
investigate the magnetic coupling of the resonant modes with bulk samples of 2, 2-diphenyl-
1-picrylhydrazyl organic radical spins. The transmission spectroscopy performed at low …