Multiferroicity in single crystals is studied using resonant soft x-ray magnetic scattering, hard x-ray diffraction, heat capacity, magnetic susceptibility, and electrical polarization. Two magnetic transitions are found at 24.6 K and . Our data are consistent with a sinusoidal spin structure at and with a helicoidal spin structure at , giving rise to ferroelectricity. Surprisingly, above , the correlation lengths of the spin structures increase as the temperature increases with dramatic changes of occurring along the axis.