We studied the technological modes of obtaining of nanoscale coatings containing a controlled number of iron atoms on a semiconductor substrate by Langmuir-Blodgett technology. We determined the regime of obtaining a  monolayer of iron arachinate with the maximum content of iron atoms into monolayer. The analysis of compression isotherms made it possible to determine the surface density of the of iron atoms. Modeling the processes of diffusion  taking into account the limited solubility Fe in CdS makes it possible to estimate the number of iron arachinate monolayers required to form a heterophase material that exhibits magnetic properties. The diffusion coefficient of Fe atoms in CdS was determined experimentally from the profile of iron distribution in CdS obtained using secondary ion mass spectrometry. The model allows to predict the density and depth of the occurrence of the nanosized iron-containing phases. It was obtained that 30 monolayers of iron arachinate obtained at pH = 5.83 provide the formation of nanosized phases at a depth of up to 300 µm. The annealing was for 30 minutes at a temperature of 450 °C.