Master's thesis presentation Theresa Fuchs

Supervisor: Vittorio Buccheri
Opponent: Nelson Rebelo
Examiner: Attila Geresdi

Abstract: The current focus of magnon-photon coupling research is on yttrium iron garnet, despite its complex fabrication processes and drawbacks in cryogenic applications. As an alternative, this thesis investigates the coupling capabilities of the ferromagnetic insulator europium sulphide (EuS). Microwave spectroscopy at cryogenic temperatures with a transverse external magnetic field is used to examine the coupling between EuS thin films and NbTiN or CuAg coplanar waveguides (CPWG). For the superconducting CPWG no stable magnon-photon coupling is observed. However, a distinct coupling signal is achieved between a Pyrex-EuS(20nm) chip and the CuAg CPWG. The saturation magnetization of EuS is determined to be 1.54 T at 15 mK, and an estimate of the Gilbert damping is obtained as 0.12. No coupling is observed when applying an external magnetic field in parallel to the microwave signal or out-of-plane. In contrast to previous literature findings, no photon-magnon coupling is observed using an InAs-EuS(20nm) chip as magnon-carrier.