Nonreciprocal reflection by magnons inFeF2: A high-resolution study

We present oblique-incidence frequency scans of an antiferromagnetic-resonance reflectivity spectrum in the presence of an applied magnetic field ${\mathit{H}}_0$. Results are shown for the c axis of an ${\mathrm{FeF}}_2$ single crystal both parallel and perpendicular to ${\mathit{H}}_0$, which is normal to the plane of incidence. In both cases the s-polarization spectra show nonreciprocal behavior with respect to ${\mathit{H}}_0$.