We have investigated the orbital magnetization of tunable two-dimensional electron-systems (2DES) in GaAs/AlGaAs-heterostructures in the magnetic quantum limit using a high-sensitive superconducting susceptometer. In particular we have studied the magnetization at filling factor v = 1, where the 2DES forms the quantum Hall ferromagnet. We extract from our data that the orbital magnetic moment is strongly enhanced at low temperatures T by spin-dependent exchange effects. Temperature dependent measurements show that in addition correlation effects dominate the excited states of the many-body system. (C) 2000 Elsevier Science B.V. All rights reserved.