Stepwise changes in electron paramagnetic resonance (EPR) parameters (integral intensity, linewidth) accompanying localization of charge carriers have been found in the α'-(BEDT-TTF)₂IBr₂ crystals. In single crystal exchange narrowing of the EPR lines and sharp decrease in static and dynamic magnetic susceptibility caused by antiferromagnetic interaction of localized charge carriers is observed at T < 50 K. At T > 50 K a difference between static and dynamic magnetic susceptibility is observed in the α'-(BEDT-TTF)₂IBr₂ crystals which is due to that the frequency of thermally activated charge carrier jumps is higher than the microwave frequency of measuring field of an EPR spectrometer.

The method of electron paramagnetic resonance (EPR) spectroscopy was used for studying magnetic and dynamic properties of phenoxyl radicals in toluene at 170-370K. Characteristics of intramolecular motion and structure of phenoxyl radicals were determined from the temperature dependence of EPR spectra. For all the given compounds the activation energies of transitions between the conformers were calculated.