Room-Temperature Femtosecond Faraday Effect in CdMnTe Single Crystals

We report the subpicosecond Faraday effect, measured in high quality Cd$_{1-x}$Mn$_{x}$Te (x = 0.12 and x = 0.09) single crystals at room temperature. Using a femtosecond pump-probe technique, we were able to generate sub-picosecond current pulses by illuminating a free-standing LT-GaAs photoswitch, couple those pulses to the CdMnTe probe crystal using a coplanar transmission line, and, finally, optically sample the temporal evolution of the resulting magnetic transients with subpicosecond resolution and the excellent signal-to-noise ratio. The ultrafast (below 600 fs) Faraday rotation, responsible for the observed magneto-optical effect, has been attributed to the ultrafast spin dynamics of holes in our p-type CdMnTe crystals. The observed femtosecond Faraday effect can be the basis for a development of a magneto-optical sampling system for ultrafast, time-resolved characterization of current transients in novel electronic and spintronic devices.