  We investigated the magnetic structure of an orthorhombic YMnO3 thin film by
resonant soft x-ray and hard x-ray diffraction. We observed a
temperature-dependent incommensurate magnetic reflection below 45 K and a
commensurate lattice-distortion reflection below 35 K. These results
demonstrate that the ground state is composed of coexisting E-type and
cycloidal states. Their different ordering temperatures clarify the origin of
the large polarization to be caused by the E-type antiferromagnetic states in
the orthorhombic YMnO3 thin film.
