EXPERIMENTAL-OBSERVATION OF MAGNETIC SURFACE-POLARITONS IN FEF2 BY ATTENUATED TOTAL-REFLECTION

We present the first direct experimental evidence for the existence of magnetic surface polaritons in a uniaxial antiferromagnet. The modes are excited in FeF2 by attenuated total reflection with the uniaxis along an applied magnetic field H-o. The resonance is observed as an attenuation of the reflected intensity as the frequency of the far-infrared beam is scanned. We find nonreciprocity between the +H-o and -H-o spectra as a consequence of the nonreciprocity of the surface polariton modes when H-o is introduced. We also observe broad dips due to the excitation of bulk modes.