Origin of the large polarization in multiferroic YMnO$_3$ thin films   revealed by soft and hard x-ray diffraction
  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. 
H. Wadati, J. Okamoto, M. Garganourakis, V. Scagnoli, U. Staub, Y.   Yamasaki, H. Nakao, Y. Murakami, M. Mochizuki, M. Nakam...
cond-mat.str-el cond-mat.mtrl-sci