  Determinant representations of form factors are used to represent the
spontaneous magnetization of the Heisenberg XXZ chain (Delta >1) on the finite
lattice as the ratio of two determinants. In the thermodynamic limit (the
lattice of infinite length), the Baxter formula is reproduced in the framework
of Algebraic Bethe Ansatz. It is shown that the finite size corrections to the
Baxter formula are exponentially small.
