Magnetic field tuning of paramagnetic frequency - temperature compensation in cryogenic sapphire dielectric microwave resonators

Abstract

Paramagnetic impurities present in sapphire dielectric microwave resonators can provide frequency - temperature compensation at liquid-helium temperatures. We demonstrate a method for `tuning' this frequency - temperature compensation by applying a uniform magnetic field parallel to the resonator axis, which induces Zeeman splitting of the electron paramagnetic resonances. This was shown for a mode at 11.84 GHz, which lies between the and electron paramagnetic resonances present in a resonator cut from Union Carbide sapphire. However, the apparent frequency dependence of the and paramagnetic susceptibilities in this dilute paramagnetic system did not obey the expected theory.