Spin relaxation through Kondo scattering in Cu/Py lateral spin valves

TL;DR

This paper investigates how Kondo scattering from magnetic impurities affects spin relaxation in Cu/Py lateral spin valves, revealing a dominant Kondo effect that reduces spin diffusion length at low temperatures.

Contribution

It demonstrates the significant role of Kondo scattering in spin relaxation, providing experimental evidence and semi-quantitative analysis of magnetic impurity effects.

Findings

Spin diffusion length decreases below 30K due to Kondo effect.

Magnetic impurities have a spin-flip probability of 34%.

Kondo scattering dominates spin relaxation even at 1 p.p.m. impurity levels.

Abstract

The temperature dependence of the spin diffusion length typically reflects the scattering mechanism responsible for spin relaxation. Within non-magnetic metals it is reasonable to expect the Elliot-Yafet mechanism to play a role and thus the temperature dependence of the spin diffusion length might be inversely proportional to resistivity. In lateral spin valves measurements have found that at low temperatures the spin diffusion length unexpected decreases. By measuring the transport properties of lateral Py/Cu/Py spin valves fabricated with different purities of Cu, we extract a spin diffusion length which shows this suppression below 30K only in the presence of the Kondo effect. We have calculated the spin-relaxation rate and isolated the contributions from magnetic impurities. We find the spin-flip probability of a magnetic impurity to be 34%. Our semi-quantitative analysis demonstrates the dominant role of Kondo scattering in spin relaxation, even in low concentrations of order 1 p.p.m., and hence accounts for the reduction in spin diffusion length observed by ourselves and others.