Conduction-electron spin resonance in cold-worked Al, Cu, and Ag: The spin-flip cross section of dislocations

We report a study of the variation with cold working of the conduction-electron spin-relaxation time in aluminum, copper, and silver by using the transmission-electron spin resonance (TESR) technique. Measurements at low temperature of the TESR linewidth before and after proper annealing of the three metals enables us to determine the effect of dislocations on the spin-relaxation rate. From the approximately linear increase of the spin-relaxation rate with resistivity it is possible to determine a spin-flip corss section. We have compared this spin-flip cross section due to the induced mechanical defects with the well-known cross section due to thermal phonons. For a given resistivity, in the case of copper and silver, we found 25 ± 10% less spin relaxation for defects than for phonons. For aluminum the defects are much more effective for spin relaxation, giving four times the expected contribution. We tentatively interpret this effect on aluminum in terms of an anisotropy of the "$g$" factor on the Fermi surface.