  A local, second-order (truncated) approximation is applied to the Hubbard
model in three dimensions. Lowering the temperature, at half-filling, the
paramagnetic ground state becomes unstable towards the formation of a
commensurate spin-density-wave (SDW) state (antiferromagnetism) and
sufficiently far away from half-filling towards the formation of incommensurate
SDW states. The incommensurate-ordering wavevector does not deviate much from
the commensurate one, which is in accord with the experimental data for the SDW
in chromium alloys.
