Conduction-electron spin resonance in aluminum at 79 GHz

Conduction-electron spin resonance in aluminum has been studied by the microwave transmission technique at 79 GHz over the temperature range 4-80 K. At low temperatures the $g$ value and linewidth show the same type of anomalous temperature dependence as reported earlier at 35 GHz. At high temperatures, where the linewidth reflects the spin-flip scattering rate from thermal phonons, a strong and unexpected frequency dependence is observed with the linewidth being proportional to the applied frequency.