Abstract
An experimental study is presented of the host 63Cu nuclear relaxation induced by paramagnetic impurities (Mn,Cr,Fe), in low external field (0G<H<1000 G) and at low temperature (1.2K<T200 G is satisfactorily described using simple spin diffusion theory, developed for the case of insulating hosts containing paramagnetic impurities. It is also shown that the strong increase of the relaxation rate below 200 G, is associated with the existence of quadrupolar effects rather than with the appearance of a new contribution to the host relaxation. The results of a quantitative analysis are reported and discussed.