Enhanced all-optical switching and domain wall velocity in annealed synthetic-ferrimagnetic multilayers

All-optical switching (AOS) of the magnetization in synthetic ferrimagnetic Pt/Co/Gd stacks has received considerable interest due to its high potential toward 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 an optimized tunnel magnetoresistance ratio. However, upon 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 have not 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 (F0) of AOS is reduced significantly as a function of annealing temperature (Ta) ranging from 100 °C to 300 °C. Specifically, a 28% reduction of F0 can be observed upon annealing at 300 °C, which is a critical Ta for MTJ fabrication. Finally, we also demonstrate a significant increase in the DW velocity in the creep regime upon annealing, which is attributed to annealing-induced Co/Gd interface intermixing. Our findings show that the annealed Pt/Co/Gd system facilitates ultrafast and energy-efficient AOS, as well as enhanced DW velocity, which is highly suitable toward opto-spintronic memory applications.