  We study effect of inhomogeneities of the lattice in the S=1/2
bond-alternating chain by using a quantum Monte Carlo method and an exact
diagonalization method. We adopt a defect in the alternating order as the
inhomogeneity and we call it `bond impurity'. Local magnetic structures induced
by the bond impurities are investigated both in the ground state and at very
low temperatures. The local magnetic structure can be looked on as an effective
S=1/2 spin and the weakness of the interaction between the local structures
causes the quasi-degenerate states in the low energy. We also investigate the
force acting between bond impurities and find that the force is generally
attractive. We also study the dynamical property of the local magnetic
structure. While the local magnetic structure behaves as an isolated S=1/2 spin
in the response to a time-dependent uniform field, it is found to be robust
against the effect of a random noise applied at each site individually in the
sweeping filed.
