Kinetic equations for a solid paramagnet in an alternating longitudinal field

Zubarev's nonequilibrium statistical operator method is used to obtain kinetic equations describing magnetic resonance in the case when the constant magnetic field is modulated by an alternating field. It is shown that the interaction of the spin system with the thermal bath cannot in general be taken into account by means of relaxation times. In the case when relaxation times can be introduced they are functions of the amplitude and frequency of the modulating field.