Symmetry Analysis of Second Harmonic Generation at Surfaces of Antiferromagnets

TL;DR

This paper uses group theory to classify and analyze the second harmonic generation response at surfaces of antiferromagnets, revealing its sensitivity to surface magnetic order and potential for imaging antiferromagnetic domains.

Contribution

It provides a symmetry-based classification of nonlinear magneto-optical responses at antiferromagnetic surfaces, including effects of additional magnetic atoms and lattice distortions.

Findings

SHG is sensitive to surface antiferromagnetism

Surface domain imaging is possible despite magnetic unit-cell doubling

Magnetic atoms and oxygen distortions influence SHG signals

Abstract

Using group theory we classify the nonlinear magneto-optical response at low-index surfaces of fcc antiferromagnets, such as NiO. Structures consisting of one atomic layer are discussed in detail. We find that optical second harmonic generation is sensitive to surface antiferromagnetism in many cases. 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 domain imaging even in the presence of magnetic unit-cell doubling.