Strong Coupling of Antiferromagnetic Resonance with Subterahertz Cavity Fields

Strong coupling of electromagnetic cavity fields with antiferromagnetic spin waves in hematite (alpha-Fe2O3) is achieved above room temperature. A cube of hematite is placed in a metallic tube and the transmission is measured, using a continuous-wave terahertz spectrometer. The spectra, collected as a function of the temperature, reveal the formation of magnetic polaritons.