Creating traveling waves from standing waves from the gyrotropic paramagnetic properties of Fe3+ ions in a high-Q whispering gallery mode sapphire resonator

We report observations of the gyrotropic change in magnetic susceptibility of the Fe3+ electron paramagnetic resonance at 12.037 GHz (between spin states |1/2> and |3/2>) in sapphire with respect to the applied magnetic field. Measurements were made by observing the response of the high-Q whispering gallery doublet in a Hemex sapphire resonator cooled to 5 K. The doublets initially existed as standing waves at zero field and were transformed to traveling waves due to the gyrotropic response.