Scaling of Kondo spin relaxation: Experiments on Cu-based nonlocal spin valves with Fe impurities

摘要

The relation between the Kondo spin-relaxation rate τ_(sK)~(-1) and the Kondo momentum-relaxation rate τ_(eK)~(-1) is explored by using nonlocal spin valves with submicron copper channels that contain dilute iron impurities. A linear relation between τ_(sK)~(-1) and τ_(eK)~(-1) is established under varying temperatures for any given device. Among 20 devices, however, τ_(sK)~(-1) remains nearly constant, despite variation of τ_(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.