MAGNETIZATION OF QUANTUM HALL SYSTEMS

The magnetic properties of a two-dimensional interacting electron syst em in a strong magnetic field are considered in the quantum Hall regim e, where the motion of the electrons is restricted to the lowest Landa u level. We apply an approach based on the many-particle quantum-field theory which we developed recently for the spin-polarized system in t he fractional quantum Hall regime, and which treats the problem of the degeneracy of a partially filled Landau level properly. Via a gauge t ransformation of the fermion Green's function, we achieve a dressing o f the propagator with multiple collective excitations. Our theory allo ws a calculation of the magnetic polarization M(T) for higher temperat ures T, where M(T)less than or similar to 0.4 is not too large. For fi lling factor nu=1 we obtain a magnetic polarization M(T) which agrees quite well with the data of a NR?IR experiment by Barrett [Phys. Rev. Lett. 74, 5112 (1995)].