Abstract
Abstract We report the experimental observation of ultrafast demagnetization associated with a significant terahertz (THz) emission in [Co/Pd] 8 multilayers (MLs) with strong perpendicular magnetic anisotropy (PMA) by using a time-resolved magneto-optical Kerr effect (TR-MOKE) magnetometer. The THz emission is associated with subsequent remagnetization which is coupled with a collective picosecond magnetization dynamics and generation of acoustic waves in these multilayers. The demagnetization time increases slightly with decreasing Co layer thickness, while no such clear trend is observed in remagnetization timescales. The anisotropy field and corresponding precession frequency show systematic increase with the decrease of Co layer thickness. However, the acoustic wave frequencies remain unchanged with Co layer thickness. The inverse of the full width at half maximum of the THz radiation varies systematically with the anisotropy field, whereas the THz peak frequency remains almost constant at around 2 THz. The origin of THz radiation is explained in terms of excitation of THz transient phonons.
Published Version
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