Temperature and magnetism of gray optical lattices

We present a theoretical investigation of the temperature and of the magnetization of atoms in one-dimensional ''gray'' optical lattices. Such lattices consist of counterpropagating beams having crossed linear polarizations, tuned on the blue side of a J --> J or a J --> J - 1 transition, and a static longitudinal magnetic field. The variation of the atomic temperature with the magnetic field recently observed (an increase at low magnetic field; a decrease towards an asymptotic value at high magnetic field) is found for any atomic transition admitting one or two uncoupled states. This change of behavior of the temperature results from a qualitative change of the cooling mechanism and is correlated with a transition from paramagnetism to antiparamagnetism in the optical lattice.