  The magnetic behaviors of a spin-1/2 alternating Heisenberg antiferromagnetic
chain in a staggered transverse magnetic field is studied by means of the
density-matrix renormalization group method and Jordan-Wigner transformation.
Quantum phase transitions of different types are observed in the S=1 Neel and
XY-like gapless phases, which result from the competitions between the
staggered transverse field and magnetic orders induced by anisotropy and
alternating interactions. The results are compared with the mean-field and some
exactly resolved results.
