  Using first-principle calculations, we demonstrate several approaches to
manipulate Dzyaloshinskii-Moriya Interaction (DMI) in ultrathin magnetic films.
First, we find that DMI is significantly enhanced when the ferromagnetic (FM)
layer is sandwiched between nonmagnetic (NM) layers inducing additive DMI in
NM/FM/NM structures. For instance, as Pt and Ir below Co induce DMI of opposite
chirality, inserting Co between Pt (below) and Ir (above) in Ir/Co/Pt trilayers
enhances the DMI of Co/Pt bilayers by 15\%. Furthermore, in case of Pb/Co/Pt
trilayers (Ir/Fe/Co/Pt multilayers), DMI can be enhanced by 50\% (almost
doubled) compared to Co/Pt bilayers reaching a very large DMI amplitude of 2.7
(3.2) meV/atom. Our second approach for enhancing DMI is to use oxide capping
layer. We show that DMI is enhanced by 60\% in Oxide/Co/Pt structures compared
to Co/Pt bilayers. Moreover, we unveiled the DMI mechanism at Oxide/Co inerface
due to interfacial electric field effect, which is different to Fert-Levy DMI
at FM/NM interfaces. Finally, we demonstrate that DMI amplitude can be
modulated using an electric field with efficiency factor comparable to that of
the electric field control of perpendicular magnetic anisotropy in transition
metal/oxide interfaces. These approaches of DMI controlling pave the way for
skyrmions and domain wall motion-based spintronic applications.
