  We study low temperature resonant spin tunneling in molecular magnets induced
by a field sweep with account of dipole-dipole interactions. Numerical
simulations uncovered formation of self-organized patterns of the magnetization
and of the ensuing dipolar field that provide resonant condition inside a
finite volume of the crystal. This effect is robust with respect to disorder
and should be relevant to the dynamics of the magnetization steps observed in
molecular magnets.
