TRANSVERSE SPIN RELAXATION OF SPIN CARRIERS DIFFUSING IN SPATIALLY PERIODIC MAGNETIC-FIELDS

An exact solution of the Bloch-Torrey equation that covers the entire range of relative diffusivities D between the spin carriers and the ma gnetic structure (due to, e.g., spin-density waves) is given for the t ransverse relaxation of an initally uniformly polarized spin system un der the influence of a magnetic field varying sinusoidally in space. E xplicit closed-form results for the short-time relaxation are obtained making use of Laplace transforms, the three-term recurrence relations associated with Mathieu's equation, and novel sum rules. At intermedi ate diffusivities the transverse polarization exhibits a novel long-ti me behaviour as a function of D.