Magnetization oscillation of a spinor condensate induced by a magnetic field gradient.

We study the spin-mixing dynamics of ultracold spin-1 atoms in a weak nonuniform magnetic field with field gradient G, which can flip the spin from +1 to -1 so that the magnetization m=ρ+-ρ- is not a constant anymore. The dynamics of mF=0 Zeeman component ?0, as well as the system magnetization m, are illustrated for both ferromagnetic and polar interaction cases in the mean-field theory. We find that the dynamics of system magnetization can be tuned between the Josephson-like oscillation similar to the case of double well and the interesting self-trapping regimes, i.e., the spin-mixing dynamics sustains a spontaneous magnetization. Meanwhile, the dynamics of ρ0 may be sufficiently suppressed for initially imbalanced number distribution in the case of polar interaction. A "beat-frequency"oscillation of the magnetization emerges in the case of balanced initial distribution for polar interaction, which vanishes for ferromagnetic interaction. [ABSTRACT FROM AUTHOR]