  We explored changes in magnetic domain structures in a magnetic layer due to
the onset of the superconductivity of an adjacent superconductive layer using
neutron reflectometry. Magnetic domain structures in 1~$\mu$m thick permalloy
(Py) films were studied as functions of magnetic field, temperature and under
the influence of the onset of superconductivity in a neighboring layer. Bragg
peaks in the off-specular scattering were observed at low fields following
saturation with an in-plane field, which are attributed to the quasi-parallel
magnetic stripes along the field direction. During the magnetization reversal
from saturation, the stripe pattern shows increases in the period, the
transverse coherence length (\textit{i.e.}, perpendicular to the stripes) and
the amplitude of the out-of-plane magnetization component. The coherence length
of the magnetic stripes is anisotropic in the remnant state with the
longitudinal coherence length (\textit{i.e.}, along the stripes) being larger
than the transverse one. The stripe period shows a weak temperature dependence
between 300~K and 3~K, but no abrupt change in the period is observed when the
temperature crosses the superconducting critical temperature.
