Thermodynamic magnetization of a strongly interacting two-dimensional system

We report thermodynamic magnetization measurements of a 2-dimensional electron gas for several high mobility Si-MOSFETs. The low-temperature magnetization is shown to be strongly sub-linear function of the magnetic field. The susceptibility determined from the zero-field slope diverges as 1/T^{\alpha}, with \alpha=2.2-2.6 even at high electron densities, in apparent contradiction with the Fermi-liquid picture.