  Spontaneous symmetry breakings, metal-insulator transitions, and transport
properties of magnetic-domain-wall states in pyrochlore iridium oxides are
studied by employing a symmetry adapted effective hamiltonian with a slab
perpendicular to the (111) direction of the pyrochlore lattice. Emergent
metallic domain wall, which has unconventional topological nature with a
controllable and mobile metallic layer, is shown to host Fermi surfaces with
modulated helical spin textures resembling Rashba metals. The helical nature of
the domain-wall Fermi surfaces is experimentally detectable by anomalous Hall
conductivity, circular dichroism, and optical Hall conductivity under external
magnetic fields. Possible applications of the domain-wall metals to
spin-current generation and "half-metallic" conduction are also discussed.
