Global entanglement in ground state of Cu₃ single-molecular magnet with magnetic field

We investigate global entanglement in the ground state of single-molecular magnet Na₉Cu₃Na₃(H₂ O)₉(α -AsW₉O₃₃)₂· 26H₂O with an external magnetic field. The concurrence, tangle, and measure function Q, which characterize the pairwise entanglement, 3-party entanglement and total entanglement, respectively, are calculated numerically at zero temperature. The results show that the magnitude and direction of the applied magnetic field play a significant role in the properties of three kinds of entanglement measures. We give a physical interpretation of the variation of the global entanglement with the magnetic field. Finally, the phase diagram of the global entanglement characterized by the critical magnetic fields is presented.