Abstract
One- and two-(Raman) particle mechanisms of the spin-lattice relaxation in nuclear and electron spin systems undergoing a phase transition are investigated. Correlations were found between temperature dependence of the SLR rate and the nature of spin-phonon interaction, frequency dispersion law of critical vibrations and temperature-frequency dependence of damping coefficient. Increasing or decreasing of critical contributions to T 1 −1 near Tc depends on correlations of these factors.