Impact of ultrafast demagnetization process on magnetization reversal in &ITL&IT10 FePt revealed using double laser pulse excitation

Ultrafast laser induced magnetization reversal in L1(0) FePt films with high perpendicular magnetic anisotropy was investigated using single- and double-pulse excitations. Single-pulse excitation beyond 10 mJ cm(-2) caused magnetization (M) reversal at the applied fields much smaller than the static coercivity of the films. For double-pulse excitation, both coercivity reduction and reversal percentage showed a rapid and large decrease with the increasing time interval (Delta t) of the two pulses in the range of 0-2 ps. In this At range, the maximum demagnetization (Delta M-p) was also strongly attenuated, whereas the integrated demagnetization signals over more than 10 ps, corresponding to the average lattice heat effect, showed little change. These results indicate that laser induced M reversal in FePt films critically relies on Delta M-P. Because Delta M-p is determined by spin temperature, which is higher than lattice temperature, utilizing an ultrafast laser instead of a continuous-wave laser in laser-assisted M reversal may reduce the overall deposited energy and increase the speed of recording. The effective control of M reversal by slightly tuning the time delay of two laser pulses may also be useful for ultrafast spin manipulation. (C) 2018 Author(s).