We investigate the spin rotational structure of magnetic skyrmions in a
tetragonal polar magnet VOSe2O5 via polarized small-angle neutron scattering
(SANS). Spin polarization analysis of the scattered neutrons provides
consistent evidence for the cycloidal spin modulation in all the incommensurate
phases at zero and non-zero magnetic field along the c axis, including the
triangular skyrmion-lattice phase. In the vicinity of the skyrmion phase, we
performed extensive SANS measurements to unravel a field-induced incommensurate
phase (IC-2 state). We discuss the possibility of anisotropic double-q state as
an alternative spin structure to provisional square skyrmion-lattice state.Comment: 27 pages, 5 figure