Superconducting properties of magnesium diboride thin film measured by using coplanar waveguide resonator

Highlights: • Study of the superconducting properties of granular disordered superconductor magnesium diboride (MgB₂). • Microwave measurements transmission properties of high-quality superconducting coplanar waveguide (CPW) resonator. • Temperature dependence of quality and resonant frequency of CPW resonator. • Hysteresis detuning of resonant frequency in changing magnetic field of artificially created RF superconducting quantum interference device (SQUID) coupled to CPW resonator. • SQUID-like behavior of CPW resonators made of granular disordered superconductors without any artificial structures in it. - Abstract: In this paper we demonstrate the superconducting properties of MgB₂ coplanar waveguide resonator patterned from 300 nm thin film fabricated by vapor deposition. We measured the temperature dependence of the quality factor and the resonant frequency of the resonator. Surprisingly, we also observed hysteretic periodic response of resonance frequency to external magnetic field, which is characteristic of bistable systems with double-well potential, such as superconducting RF SQUID or phase-slip flux qubits. This property seems to be peculiar for granular and disordered superconductors where a superconducting loop of large effective diameter with weak links can be formed