The spin-lattice relaxation time ${\mathrm{\tau }}_{\mathit{s}\mathit{l}}$ is the characteristic time needed for the energy transfer between the lattice and the spin system. It is demonstrated that ${\mathrm{\tau }}_{\mathit{s}\mathit{l}}$ can be determined with laser-induced spin-polarized photoemission. Upper and lower limits are derived from a single-pulse experiment using pulses of various time durations. It is found that ${\mathrm{\tau }}_{\mathit{s}\mathit{l}}$ of iron is shorter than 20 ns but longer than 30 ps. A direct measurement of ${\mathrm{\tau }}_{\mathit{s}\mathit{l}}$ is possible with a pump-probe experiment. One laser pulse heats the sample and a second time-delayed pulse is used to probe the magnetic state. ${\mathrm{\tau }}_{\mathit{s}\mathit{l}}$ is found to be 100±80 ps for ferromagnetic gadolinium.

• Received 13 January 1992

DOI:https://doi.org/10.1103/PhysRevB.46.5280