Energy transfer from paramagnetic ions to a lattice through rapidly relaxing centers

Spin-lattice relaxation is analyzed in a crystal containing two types of paramagnetic centers having approximately equal resonant frequencies but markedly different spin-phonon couplings. It is assumed that for the centers having the strong spin-phonon coupling this coupling is stronger than the spin-spin coupling with other paramagnetic centers. The Green's function method is used. The spin-lattice relaxation time for the centers coupled weakly with the lattice through rapidly relaxing centers is found as a function of the difference between the splittings of their spin levels, the strength of the spin-spin coupling between these centers, the concentrations of these centers, and the strength of the spin-phonon coupling over rapidly relaxing centers.Translated from Izvestiya VUZ. Fizika, No. 3, pp. 15–20, March, 1970.In conclusion the author thanks S. A. Al'tshuler and L. K. Aminov for useful discussions of these results.