  The magnetization of a two-dimensional ferromagnetic Heisenberg model, which
represents a quantum Hall system at filling factor nu=1, is calculated
employing a large N Schwinger boson approach. Corrections of order 1/N to the
mean field (N=infinity) results for both the SU(N) and the O(N) generalization
of the bosonized model are presented. The calculations are discussed in detail
and the results are compared with quantum Monte Carlo simulations as well as
with recent experiments. The SU(N) model describes both Monte Carlo and
experimental data well at low temperatures, whereas the O(N) model is much
better at moderate and high temperatures.
