Spin-spin relaxation in magnetically dilute crystals

Abstract

Magnetic resonance is examined in paramagnetic systems with a small concentration of spins. The free induction signal (FIS) and resonance line shape function (LSF) are calculated. The theory is based on the introduction of an auxiliary system where one spin does not have a flip-flop interaction with the surroundings. The FIS is calculated for this spin using the Anderson-Weiss-Kubo theory and its memory function is used to construct the memory of the main system. The needed numerical coefficients are obtained from expansions of the FIS in terms of the concentration. Here the polarization transport in magnetically dilute systems is taken into account for the first time. This is shown to lead to significant slowing down of the decay in the FIS for times longer than the phase relaxation time. Existing experimental data are compared with theoretical models. Satisfactory agreement is obtained for the description of the central part of the LSF after an additional experimentally observed broadening is introduced in the theory. Data on the amplitude and position of the sideband peaks from the different experiments are not in good agreement with one another or with the theory.

NMR line shape of Si29 in single-crystal silicon

“…Coherent many-body quantum dynamics of nuclear spins in solids is an old subject, dating back to observations of the free-induction-decay in CaF 2 , a cubic array of spin-1/2 19 F nuclei coupled by magnetic dipole interactions.…”

Concentration dependence of the wings of a dipole-broadened magnetic resonance line in magnetically diluted lattices

“…Отсюда получаем логарифмическую концентрационную зависимости координаты особой точки АКФ следующего вида: уравнениях и выполнить численные расчеты, аналогичные расчетам, проведенным в работах [13,27].…”