The s=1/2 chain-boundary excitations occurring in the Haldane phaseof s=1
antiferromagnetic spin chains are investigated. The bilinear-biquadratic
hamiltonian is used to study these excitations as a function of the strength of
the biquadratic term, β, between −1≤β≤1. At the AKLT point,
β=−1/3, we show explicitly that these excitations are localized at the
boundaries of the chain on a length scale equal to the correlation length
ξ=1/ln3, and that the on-site magnetization for the first site is
=2/3. Applying the density matrixrenormalization group we show that
the chain-boundaryexcitations remain localized at the boundaries for
−1≤β≤1. As the two critical points β=±1 are approached the
size of the s=1/2 objects diverges and their amplitude vanishes.Comment: 4 Pages, 4 eps figures. Uses RevTeX 3.0. Submitted to PR