Ultrafast magnetization dynamics in the half-metallic Heusler alloy Co2FeAl

We report on optically induced, ultrafast magnetization dynamics in the Heusler alloy ${\mathrm{Co}}₂\mathrm{FeAl}$, probed by time-resolved magneto-optical Kerr effect. Experimental results are compared to results from electronic structure theory and atomistic spin-dynamics simulations. Experimentally, we find that the demagnetization time (${\ensuremath{\tau}}_M$) in films of ${\mathrm{Co}}₂\mathrm{FeAl}$ is almost independent of varying structural order, and that it is similar to that in elemental $3d$ ferromagnets. In contrast, the slower process of magnetization recovery, specified by ${\ensuremath{\tau}}_R$, is found to occur on picosecond time scales, and is demonstrated to correlate strongly with the Gilbert damping parameter ($\ensuremath{\alpha}$). Based on these results we argue that for ${\mathrm{Co}}₂\mathrm{FeAl}$ the remagnetization process is dominated by magnon dynamics, something which might have general applicability.