  The superfluid-Mott insulator transition of spin-2 boson atoms with repulsive
interaction in an optical lattice in a magnetic field is presented. By using
the mean field theory, Mott ground states and phase diagrams of superfluid-Mott
insulator transition at zero temperature are revealed. Applied magnetic field
leads to some phase boundaries splitting. For all the initial Mott ground
states containing multiple spin components, different spin components take on
different phase boundaries. It is found that in this system the phase
boundaries with different magnetization can be moved in different ways by only
changing the intensity of the applied magnetic field.
