A new parameter of compounds of different nature (organic, inorganic, single- and polycrystal ones) containing complexes with magnetic probes has been developed. That is the height of the potential barrier of the crystal field. The barrier height characterizes the nature of the neighbor structure of a complex with a magnetic ion that can be distorted in accordance with the nature or the growth technology of the compound. To analyze the spectra of electron spin resonance of the Fe3+ ions in organic compounds of different structure symmetry in temperature range of 4.2 K-295 K, models of the effect of multi-minimum potential of crystal field were used.