Spin structures of magnetic phases in YMn2O5

A magnetic ferroelectric material, YMn2O5, undergoes several magnetic phase transitions at low temperatures and develops spontaneous electric polarization along the b-axis in a commensurate magnetic phase with a characteristic wave vector of (0.5,0,0.25). We have determined the commensurate spin structure by performing four circle neutron diffraction (FCD) and three-dimensional polarization analysis (CRYOPAD) on a single crystal of YMn2O5. In the spin structure, Mn4+ moments form a transverse (cycloidal) spiral structure along the c-axis that can induce the spontaneous electric polarization along the b-axis.