Switching microwave dielectric resonators from a high-Q on state to an off state using low-field electron paramagnetic resonance transitions

We show that the application of a small (<75 G) magnetic field can be used to switch a low-loss microwave dielectric to a high-loss material. This enables high performing microwave dielectric resonators and filters to be switched between a high-Q on state and a low-Q off state electronically. In this study, the absorption mechanism inducing the low Q state is from electron paramagnetic resonant transitions of an Fe³⁺ state in a host Al₂O₃ dielectric. Our modeling efforts show that it is possible to further optimize the performance of these switchable devices through a material selection process, which will entail the choice of host lattice and the J > impurity and its concentration.