  An analytical model for the domain wall structure in ultrathin films with
perpendicular easy axis and interfacial Dzyaloshinskii-Moriya interaction,
submitted to an arbitrary in-plane magnetic field, is presented. Its solution
is simplified to the numerical minimization of an analytic function of just one
variable. The model predictions are compared to numerical micromagnetic
simulations, using parameters of existing samples, revealing a very good
agreement. Remaining differences are analyzed, and partly corrected.
Differences with the predictions of the simplest model, usually found in the
literature, in which only the domain wall moment's in-plane orientation can
vary, are exemplified. The model allows accurate computations, as a function of
in-plane field module and orientation, of the domain wall tension and width,
quantities controlling the creep motion of domain walls in such films.
