  We investigate two-component ultracold fermions loaded into a decorated
square lattice, which are described by the Hubbard model with repulsive
interactions and nearest neighbor hoppings. By combining the real-space
dynamical mean-field theory with the numerical renormalization group method, we
discuss how a ferromagnetically ordered ground state in the weak coupling
regime, which originates from the existence of a dispersionless band, is
adiabatically connected to a Heisenberg ferrimagnetic state in the strong
coupling limit. The effects of level splitting and hopping imbalance are also
addressed.
