A theory of the 'phonon bottleneck' in the Orbach process of spin-lattice relaxation

Publisher Website
Google Scholar
Abstract
A theory of the 'bottleneck' which restricts relaxation by the Orbach mechanism when too few phonons of the appropriate frequencies are available is developed for the case of a spin doublet relaxing via a single excited level. The extent to which the relaxation disturbs the distribution of phonons is found on the assumption that the only broadening of the two bands of lattice modes concerned is that associated with the finite lifetime of the excited spin level. The relaxation is hindered most when the splitting of the doublet in an applied magnetic field H is such that the bands are well separated. Otherwise overlap between them reduces the effect of the bottleneck, so that it disappears as H approaches zero.