We report time-resolved Kerr effect measurements of magnetization dynamics in ferromagnetic SrRuO${}_3$. We observe that the demagnetization time slows substantially at temperatures within 15 K of the Curie temperature, which is $~$150 K. We analyze the data with a phenomenological model that relates the demagnetization time to the spin-flip time. In agreement with our observations, the model yields a demagnetization time that is inversely proportional to $T-T_c$. We also make a direct comparison of the spin-flip rate and the Gilbert damping coefficient, showing that their ratio is very close to $k_B{T}_c$, indicating a common origin for these phenomena.

• Received 28 July 2010

DOI:https://doi.org/10.1103/PhysRevB.83.134432