We study the ground state properties of a spin-3 Cr condensate subject to an
external magnetic field by numerically solving the Gross-Piteavskii equations.
We show that the widely adopted single-mode approximation is invalid under a
finite magnetic field. In particular, a phase separation like behavior may be
induced by the magnetic field. We also point out the possible origin of the
phase separation phenomenon.Comment: 6 pages, 5 figure