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Theory of electron spin echo for incoherent electron hopping on sites with randomly oriented nuclear spins.

The influence of incoherent hopping of electrons on the spin-echo phenomenon is investigated. The model considered includes the random local precession frequencies of the electron spin caused by interaction with randomly oriented nuclear spins. The incoherent hopping is modeled by stochastic transition amplitudes. A general, asymptotically exact expression has been found that describes the dependence of the echo signal on the time delay and on the size and structure of the clusters available for the hopping electron