Multi-impurity effects on the entanglement of anisotropic Heisenberg   ring XXZ under a homogeneous magnetic field
  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 
Gao Wen Bin, Yang Guo Hui and Zhou Ling