Topography of antiferromagnetic domains using second harmonic generation with an external reference

Abstract
O3, in which the time-invariant second-harmonic reference can be generated either intrinsically by the crystal or externally by use of the new technique, so that both methods may be compared. The technique is then used to visualize the domain structure of YMnO3, an antiferromagnetic crystal which does not provide the time-invariant reference wave intrinsically. The experiments demonstrate the wide applicability of the method.