  We examine the atomic intermixing phenomenon in three distinct amorphous
CoB-based multilayer thin film platforms - Pt/CoB/Ir, Ir/CoB/Pt and Pt/CoB/MgO
- which are shown to stabilise room-temperature chiral magnetic textures.
Intermixing occurs predominantly between adjacent metallic layers. Notably, it
is stack-order dependent, and particularly extensive when Ir sits atop CoB.
Intermixing induced variations in magnetic properties are ascribed to the
formation of magnetic dead layer arising from CoIr alloying in the metallic
stacks. It also produces systematic variations in saturation magnetization, by
as much as 30%, across stacks. Crucially, the resulting crossover CoB thickness
for the transition from perpendicular to in-plane magnetic anisotropy differs
by more than 2x across the stacks. Finally, with thermal annealing treatment
over moderate temperatures of 150-300 degree Celsius, the magnetic anisotropy
increases monotonically across all stacks, coupled with discernibly larger Hc
for the metallic stacks. These are attributed to thermally induced CoPt
alloying and MgO crystallization in the metallic and oxide stacks,
respectively. Remarkably, the CoB in the Pt/CoB/MgO stacks retains its
amorphous nature after annealing. Our results set the stage for harnessing the
collective attributes of amorphous CoB-based material platforms and associated
annealing processes for modulating magnetic interactions, enabling the tuning
of chiral magnetic texture properties in ambient conditions.
