Coplanar cavity for strong coupling between photons and magnons in van der Waals antiferromagnet

We investigate the performance of niobium nitride superconducting coplanar waveguide resonators toward realizing hybrid quantum devices with magnon-photon coupling. We find internal quality factors similar to 20 000 at 20 mK base temperature, in zero magnetic field. We find that by reducing film thickness below 100nm, an internal quality factor greater than 1000 can be maintained up to a parallel magnetic field of similar to 1T and a perpendicular magnetic field of similar to 100mT. We further demonstrate strong coupling of microwave photons in these resonators with magnons in chromium trichloride, a van der Waals antiferromagnet, which shows that these cavities serve as a good platform for studying magnon-photon coupling in 2D magnonics based hybrid quantum systems. We demonstrate strong magnon-photon coupling for both optical and acoustic magnon modes of an antiferromagnet.