Surface resonance enhanced Goos-Hänchen shifts for different orientations of antiferromagnets in the presence of an applied magnetic field

When reflection takes place off the surface of antiferromagnets, surface resonances, considered as an extension of surface polariton dispersion curves into the reflection region, can enhance the lateral shift of the reflected beam in the presence of an external magnetic field. The effect was earlier studied for both the applied field and the antiferromagnet easy axis perpendicular to the plane of incidence in the case of a small applied field. Here, using MnF${}_2$ as the antiferromagnet, we extend the work to look at how increasing the field and changing the antiferromagnet orientation affects the results, which always display nonreciprocity. We find that, when the antiferromagnet easy axis is parallel to the surface within the plane of incidence, leading to spin canting, enhanced shifts in the reflection region occur in much the same way as when the easy axis is along the applied field direction, but an applied field an order of magnitude higher is needed. However, when the easy axis is perpendicular to the surface even higher fields are necessary, and it is difficult to achieve such enhanced shifts.