The notion of relaxation gate is introduced. On its basis, a simple Jordan type model of relaxation is proposed. This model enables the derivation of a formula relating the magnetic after-effect constant with the energy-barrier distribution of microregion magnetization. The magnetic aftereffect constant Sothe remanence , and the coercive force Hcwere measured at different aging times for a polycrystal and single crystals of Cu-1-percent Co alloy at a temperature of 600°C. The measurements were performed with a specially adapted measuring arrangement. From the derived formula and data obtained from magnetic measurements, it was found that both heterogenous and homogenous groups of particles become precipitated. At a certain stage of aging, the stable homogenous particles become converted from independent particles into strongly interacting ones.