Аннотация:Electron paramagnetic resonance (EPR) spectroscopy and magnetic susceptibility measurementsare used to study samples of ceramic solid solutions CuCr1 – xMgxO2 (x = 0–0.013). An analysis of the temperaturedependences of the EPR linewidth, static magnetic susceptibility, and the effect of illumination onthe EPR spectra indicates two mechanisms for the effect of magnesium doping on the magnetic properties of copper chromite. The substitution of chromium by magnesium in the crystal lattice suppresses antiferromagnetic fluctuations and leads to a decrease in the EPR linewidth and an increase in magnetic susceptibility at a temperature close to the temperature of the antiferromagnetic transition. An increase in the concentration of mobile holes leads to a decrease in the spin relaxation time of chromium ions. The data obtained are of interest both for fundamental physics and for practical applications in the field of solar energy.