Magnetization plateau in anS=32antiferromagnetic Heisenberg chain with anisotropy

The magnetization process of the $S$=$\frac{3}{2}$ antiferromagnetic Heisenberg chain with single-ion anisotropy $D$ at $T=0\mathrm{}$ is investigated by the exact diagonalization of finite clusters and finite-size scaling analyses. It is found that a magnetization plateau appears at $m=$ $\frac{1}{2}$ for $D>\mathrm{}{D}_c=0.93\mathrm{}\pm 0.01$. The phase transition with respect to $D$ at $D_c$ is revealed to be of the Kosterlitz-Thouless type. The magnetization curve of the infinite system is also presented for some values of $D$.