  We have investigated magnetic structures of the centrosymmetrric skyrmion
material Gd2PdSi3 by means of polarized neutron scattering near zero field with
an isotope-160Gd-enriched single crystal. In a previous study, magnetic
structures in Gd2PdSi3 at low temperatures were studied by resonant X-ray
scattering measurements [T. Kurumaji et al. Science 365, 914 (2019)]. The
present polarized neutron results confirm that the magnetic structure in zero
field has elliptic screw-type magnetic modulation with a propagation vector of
(q, 0, 0) with q ~ 0.14 and its equivalents. As the temperature increases, the
system undergoes a magnetic phase transition while keeping the incommensurate
q-vector of (q,0,0). We found that the thermally-induced phase has sinusoidal
magnetic modulations with magnetic moments perpendicular both to the c axis and
to the q-vector. We also investigate the spin-helicity degree of freedom in the
ground state by polarized neutrons, revealing that the system contains equal
fractions of the left-handed and right-handed screw-type orders as expected
from the centrosymmetric crystal structure.
