  We have examined magnetic ordering of the two-dimensional (2D) bilayer
manganite La$_{1.1}$Sr$_{1.9}$Mn$_2$O$_7$ with neutron diffraction technique.
Due to the two-dimensionality, there appears intense 2D ridge scattering along
the tetragonal $(00l)$ direction, and the analyses of such scattering leads to
a conclusion that the low temperature spin structure is a canted
antiferromagnetic ordering.
