  All optical switching (AOS) of the magnetization in synthetic ferrimagnetic
Pt/Co/Gd stacks has received considerable interest due to its high potential
towards integration with spintronic devices, such as magnetic tunnel junctions
(MTJs), to enable ultrafast memory applications. Post-annealing is an essential
process in the MTJ fabrication to obtain optimized tunnel magnetoresistance
(TMR) ratio. However, with integrating AOS with an MTJ in prospect, the
annealing effects on single-pulse AOS and domain wall (DW) dynamics in the
Pt/Co/Gd stacks haven't been systematically investigated yet. In this study, we
experimentally explore the annealing effect on AOS and field-induced DW motion
in Pt/Co/Gd stacks. The results show that the threshold fluence (F_0) for AOS
is reduced significantly as a function of annealing temperature (T_a) ranging
from 100C to 300C. Specifically, a 28% reduction of F_0 can be observed upon
annealing at 300C, which is a critical T_a for MTJ fabrication. Lastly, we also
demonstrate a significant increase of the DW velocity in the creep regime upon
annealing, which is attributed to annealing-induced Co/Gd interface
intermixing. Our findings show that annealed Pt/Co/Gd system facilitates
ultrafast and energy-efficient AOS, as well as enhanced DW velocity, which is
highly suitable towards opto-spintronic memory applications.
