⁶³Cu spin lattice relaxation in CuMn: nuclear spin diffusion

The recovery of the ⁶³Cu nuclear magnetization in dilute CuMn alloys has been studied over wide ranges of field and temperature (1<H<51 kG, 0.32<T<77 K). Depending on the experimental conditions exp-(t/T₁) or exp-(t/ tau )^1/2 behaviours, characteristic respectively of rapid diffusion and diffusionless regimes, have been observed. In intermediate cases the analysis of the shape of the recovery allows a quantitative determination of the diffusion barrier b. The number n_b of nuclear sites within b depends linearly on the impurity magnetization. All the results can be explained by simple models. The diffusion barrier, which has been ignored until now in dilute alloys, is shown to play a large role in the interpretation of the relaxation data in such systems.