Role of the dipole reservoir in low-frequency absorption in paramagnetic systems with restricted spectral diffusion

Abstract

The absorption of energy from the transverse low-frequency (LF) field by inhomogeneously broadened paramagnetic systems is studied theoretically taking into account the electronic dipole-dipole reservoir. The case of restricted spectral diffusion is studied. It is shown that LF absorption is associated with effective interactions of the type S/sup z/S/sup z/ and S/sup +/-/S/sup -/+/ and appears in second-order perturbation theory. The relative change in the magnetization of the spin system, owing to LF absorption in the presence of simultaneous interaction of a saturating microwave field with the system, is calculated. The dependence of the change in the magnetization on the parameters of the LF field and on the magnitude of the microwave detuning is analyzed. The theoretical results are in satisfactory agreement with the experimental results.