Tunable magneto-optical effects in antiferromagnetic structures

Close to the magnon resonance frequency, antiferromagnets act as indefinite permeability media, i.e., not all their permeability tensor components are of the same sign. This behavior can induce a series of optical effects such as all-angle negative refraction. In the presence of an external field, a non-reciprocal lateral shift on reflection is also possible. We illustrate these effects using the example of MnF₂. In this crystal both the angle of refraction and the Goos-Hänchen shift become tunable when an external magnetic field is applied.