  The properties of surface Dirac Fermions on a 3D topological insulator in
proximity to a magnetic insulator with spatially textured magnetization are
considered. We present an exact analytical treatment of the spectrum, the bound
states and the domain wall resistance for an extended generic domain wall with
in-plane and out-of-plane magnetizations. In the latter case, we find
oscillations in the domain wall resistance as a function of the wall width and
for certain widths a complete absence of reflections for all incoming momenta.
The surprising occurrence of oscillations and the reflectionless potentials can
be related to a supersymmetry of the surface Dirac Hamiltonian combined with
the domain wall profile.
