  Surfaces and interfaces of magnetic nanostructures can reveal rather
interesting and unusual properties that differ substantially from those of
bulky materials. Here we apply the surface-sensitive method of optical second
harmonic generation (SHG) for the studies of magnetization induced effects that
appear in the nonlinear reflection from interfaces between ferromagnetic (Co)
and heavy metals (Pt, Ta, W, Au, Ag, Cu). We demonstrate the appearance of
magnetization induced variation in the p-polarized SHG intensity in the
geometry of the longitudinal magneto-optical Kerr effect that is forbidden for
homogeneous magnetic structures. This confirms the existence of chiral magnetic
states at heavy metal/ferromagnet interfaces that appear due to the
surface-induced Dzyaloshinskii-Moriya interaction. The related nonlinear
chiroptical effect in the SHG intensity is proportional to the dc
flexo-electric polarization that is shown to exist for chiral magnetic states
at the considered interfaces.
