Resonant and nonresonant conduction-electron-spin transmission in normal metals

The propagation of nonequilibrium conduction-electron magnetization of paramagnetic metals under resonant and nonresonant conditions is described by a simple model and investigated experimentally. The theory is in qualitative agreement with the 9-GHz transmission experiments on high-purity paramagnetic metals coated with ferromagnetic layers to selectively enhance spin transmission. Observations on (i) the temperature dependence of the transmission electron-spin resonance (TESR) in Cu, Ag, and Au; (ii) on the anisotropy of the TESR at helium temperature in Cu, and Au; and (iii) a nonresonant single-particle spin-wave mode in Cu, Au, and W are reported. The nonresonant spin waves are attributed to ballistic electrons which cross the sample without momentum scattering. At low temperatures these waves give the major part of the nonequilibrium magnetization. Both transverse and longitudinal modes are observed.