  The relation between the Kondo spin relaxation rate $ {\tau_{sK}}^{-1} $ and
the Kondo momentum relaxation rate $ {\tau_{eK}}^{-1} $ is explored by using
nonlocal spin valves with submicron copper channels that contain dilute iron
impurities. A linear relation between $ {\tau_{sK}}^{-1} $ and $
{\tau_{eK}}^{-1} $ is established under varying temperatures. However, under
varying impurity concentrations, ${\tau_{sK}}^{-1}$ remains nearly constant
despite variation of $ {\tau_{eK}}^{-1} $ by a factor of 10. This surprising
relation can be understood by considering spin relaxation through overlapping
Kondo screening clouds and supports the physical existence of the elusive Kondo
clouds.
