Microwave absorption signals under conditions of saturation of nonequidistant levels (S=3/2) of paramagnets at low temperatures

Abstract

Theoretical expressions are derived for the absorption signals X"(m, ~) for a detecting microwave field having a frequency m with saturation of a pair of levels of a nonequidistant spectrum of a paramagnet (S = 3/2) by a microwave field with frequency ~ at low temperatures under conditions when the dipole-~ipole spin reservoir is not in equilibrium with the lattice. The expected behavior of X"(~, ~), in particular, the jump in the position of the absorption signal at the point of bifurcation ~ = ~b as well as jumps from a metastable state of equilibrium into a stable state with ~ > ~b, occurring under certain conditions, are described in the case of a strong low-temperature shift in the frequency of the saturated transition.