  The effects of multi-impurity on the entanglement of anisotropic Heisenberg
ring XXZ under a homogeneous magnetic field have been studied. The impurities
make the equal pairwise entanglement in a ring compete with each other so that
the pairwise entanglement exhibits oscillation. If the impurities are of larger
couplings, both the critical temperature and pairwise entanglement can be
improved
