speed dependence on $H_{x}$ has been related to the variation of domain wall energy [@Je2013]. The DDW width (resp. DW energy) is expected to have a minimum (resp. maximum) value when the applied in-plane field is equal and opposite to the stabilising $H_{\mathrm{DMI}}$ field i.e. when the DW acquires a Bloch form. In the two DW propagation regimes, this is the $H_{x}$ field for which the DW speed is predicted to exhibit a minimum. With these assumptions, $H_{x}$ could therefore be a direct measure of the DMI energy density $D$, provided that the domain wall width parameter $\Delta= \sqrt{A/K_{0}}$ ($K_{0}$ being the effective uniaxial anisotropy and $A$ the exchange constant) and $M_{s}$ are known.

In the following, we will show that the DW speed *vs.* in-plane field curves in the creep regime cannot in general be used to extract the strength and the sign of the DMI, as was done for Pt/Co/Pt samples [@Je2013; @Hrabec2014]. Moreover, we find that the $v(H_{x})$ curves measured for the same sample in the thermally activated and in the flow regimes can have different trends. Although the mechanism determining the exact trend of the velocity curves in the creep regime is not clear, we show 