Direct observation of a nuclear spin diffusion barrier

Abstract

Experiments are reported which measure the relaxation properties of nuclei near a paramagnetic impurity. For Y(C2H5SO4)3•9H2O: Yb3+, nuclei as close as 3 to the Yb ion are in strong thermal contact with the bulk spins, contradicting the traditional notions of the diffusion barrier. I present evidence that impurity-induced diffusion and interaction with the electron spin-spin reservoir are important processes which act to reduce the barrier dimension. © 1973 The American Physical Society.