AbstractThe EPR spectrum of the Cu2+ion in octahedral environment is calculated with the account of the Jahn‐Teller effect within the cluster model. The study of the frequency dependence of the EPR spectrum is used as a basis for the estimation of parameters of the Hamiltonian describing the behaviour of the system. The appearance of an additional isotropic line and drop of intensities of the resonance lines of the low temperature spectrum with the temperature increase are explained on the basis of the population of a great number of excited states and their propertie