  Multiferroicity in LiCu2O2 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 (T1) and 23.2 K (T2). Our data are consistent with a sinusoidal spin
structure at T2<T<T1 and with a helicoidal spin structure at T<T2 giving rise
to ferroelectricity. Surprisingly, above T2 the correlation lengths of the spin
structures increase as the temperature increases with dramatic changes of ~42%
along the c-axis. Our results demonstrate the interplay of the geometrical
frustration and the electronic and magnetic polarizations.
