Symmetry analysis of second-harmonic generation at surfaces of antiferromagnets

Using group theory we classify the nonlinear magneto-optical response at lo w-index surfaces of fee antiferromagnets, such as NiO. Structures consistin g of one atomic layer are discussed in detail. We find that optical second- harmonic generation is sensitive to surface antiferromagnetism in many case s. We discuss the influence of a second type of magnetic atoms, and also of a possible oxygen sublattice distortion on the output signal. Finally, our symmetry analysis yields the possibility of antiferromagnetic surface doma in imaging even in the presence of magnetic unit-cell doubling.