Dynamic demagnetization in magnetic thin films using a new pump-probe system in the 6 femtosecond range

Time resolution limited dynamic measurements show the need for improved techniques to access ultrafast demagnetisation processes on the sub-10 femtosecond timescale. We have constructed a state-of- the-art time-resolved magneto-optic Kerr effect (TR-MOKE) apparatus for the observation of ultrafast demagnetization and precessional dynamics in ferromagnetic materials. Our system can operate well below the current ranges used by most researchers (typically in the region of 40 fs). Using current ultrafast optical methods of pulse compression, designed to obtain unprecedented temporal resolution, we have developed a dual-colour pump-probe technique: This enables us to attain an ultimate resolution in the 12 fs range, the spectral range being split between pump and probe beams. We have demonstrated that the system has the capacity for ultrafast demagnetization measurements using a GdFeCo thin film. Future developments will employ the full spectral range in both pump and probe branches to reach an expected temporal resolution in the vicinity of 6 fs, corresponding to few-cycle pulses.