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 wave vector does not deviate much from the commensurate one, which is in accordance with the experimental data for the SDW in chromium alloys.

• Received 25 April 1996

DOI:https://doi.org/10.1103/PhysRevB.55.942