  We present a systematic analysis of our ability to tune chiral
Dzyaloshinskii-Moriya Interactions (DMI) in compensated ferrimagnetic
Pt/GdCo/Pt1-xWx trilayers by cap layer composition. Using first principles
calculations, we show that the DMI increases rapidly for only ~ 10% W and
saturates thereafter, in agreement with experiments. The calculated DMI shows a
spread in values around the experimental mean, depending on the atomic
configuration of the cap layer interface. The saturation is attributed to the
vanishing of spin orbit coupling energy at the cap layer and the simultaneous
constancy at the bottom interface. Additionally, we predict the DMI in
Pt/GdCo/X (X=Ta, W, Ir) and find that W in the cap layer favors a higher DMI
than Ta and Ir that can be attributed to the difference in d-band alignment
around the Fermi level. Our results open up exciting combinatorial
possibilities for controlling the DMI in ferrimagnets towards nucleating and
manipulating ultrasmall high-speed skyrmions.
