  We consider an alternating Heisenberg spin-$1/2$
antiferromagnetic-ferromagnetic ($AF-F$) chain with the space modulated
dominant antiferromagnetic exchange and anisotropic ferromagnetic coupling
(tetrameric spin-$1/2$ chain). The zero-temperature effect of a symmetry
breaking transverse magnetic field on the model is studied numerically. It is
found that the anisotropy effect on the ferromagnetic coupling induces two new
gapped phases. We identified their orderings as a kind of the
stripe-antiferromagnetic phase. As a result, the magnetic phase diagram of the
tetrameric chain shows five gapped quantum phases and the system is
characterized by four critical fields which mark quantum phase transitions in
the ground state of the system with the changing transverse magnetic field. We
have also exploited the well known bipartite entanglement (name as concurrence)
and global entanglement tools to verify the occurrence of quantum phase
transitions and the corresponding critical points.

Strongly Correlated Electrons