  We consider the magnetic phase diagram of the two-dimensional Hubbard model
on a square lattice. We take into account both spiral and collinear
incommensurate magnetic states. The possibility of phase separation of spiral
magnetic phases is taken into consideration as well. Our study shows that all
the listed phases appear to be the ground state at certain parameters of the
model. Relation of the obtained results to real materials, e.g. Cu-based
high-temperature superconductors, is discussed.
