  The N\'eel state in fermionic mixtures of two pseudospin species in an
optical lattice is analyzed at low temperatures. Experimentally it remains a
challenge to demonstrate antiferromagnetic correlations in ultracold fermionic
quantum gases. We find that, while in balanced systems the N\'eel order
parameter can point in any spatial direction, in imbalanced mixtures
antiferromagnetism is strictly perpendicular to the quantization axis (i.e.,
the z-axis). Since, experimentally, one always has to assume some minimal
imbalance this should have important consequences for ongoing experiments.

Quantum Gases