Observation of an Anomalous Frequency Dependence of the Conduction-Electron Spin Resonance in Al

Abstract

New data at 1.27 GHz for conduction-electron spin resonance (CESR) in aluminum are reported. When analyzed in conjunction with our previous data at 9.2 and 35 GHz, we are unable to interpret all the CESR data in terms of existing theory which incorporates $g$ anisotropy and many-body effects, and assumes as frequency independent the phonon, impurity, and surface contributions to the spin relaxation. Analogous data for copper are consistent with the theory.