  We describe a field-driven domain wall creep-based method for the
quantification of interfacial Dzyaloshinskii-Moriya interactions (DMI) in
perpendicularly magnetized thin films. The use of only magnetic fields to drive
wall motion removes the possibility of mixing with current-related effects such
as spin Hall effect or Rashba field, as well as the complexity arising from
lithographic patterning. We demonstrate this method on sputtered Pt/Co/Ir/Pt
multilayers with a variable Ir layer thickness. By inserting an ultrathin layer
of Ir at the Co/Pt interface we can reverse the sign of the effective DMI
acting on the sandwiched Co layer, and therefore continuously change the domain
wall (DW) structure from right- to the left-handed N\'{e}el wall. We also show
that the DMI shows exquisite sensitivity to the exact details of the atomic
structure at the film interfaces by comparison with a symmetric epitaxial
Pt/Co/Pt multilayer.
