Direct measurement of the conduction electron spin-lattice relaxation time T-1 in gold

A time-resolved technique for the direct measurement of the conduction electron spin-lattice relaxation time T-1 is Introduced. The method is based on the detection of the polar Kerr rotation induced by optically switched picosecond risetime transient magnetic fields. Demonstrated on polycrystalline gold films, the first direct measurement of T-1 in a metal is presented. The measured value T-1 - 45 +/- 5 ps suggests that Matthiessen's rule is not obeyed for conduction electron spin scattering. The technique can be applied at room temperature to a variety of conduction electron systems with spin relaxation times as short as a few ps.