  A comparative experimental investigation of the dependence of second harmonic
generation (SHG) on applied external voltage between the standard nematic
liquid crystalline material and an analogue ferromagnetic nematic liquid
crystalline material was performed by using a fundamental optical beam at 800
nm wavelength. For a ferromagnetic material, the dependence of SHG on an
applied magnetic field was also examined. Three different polarization
combinations of the fundamental and the second harmonic radiation were
analysed. The SHG signal observed in the former material is attributed to a
combination of electric field-induced SHG (EFISHG) and flexoelectric
deformation-induced SHG, while SHG signal observed in the latter material is
attributed solely to flexoelectric deformation-induced SHG. The obtained
dependences of the SHG signal on the associated optical retardation show that
in the most favourable polarization combination the two contributions generate
about the same effective nonlinear optical susceptibility.
