ITINERANT-ELECTRON MAGNETISM IN THE QUANTUM HALL REGIME

The two-dimensional interacting electron gas at Landau level filling f actor v = 1 at temperature T = 0 is a strong ferromagnet; all spins ar e completely aligned by arbitrarily weak Zeeman coupling. We report on a theoretical study of its thermodynamic properties, particularly the temperature dependence of the spin magnetization. Our study is based on an approximation in which the self-energy includes contributions ob tained by summing up particle-hole ladders which take into account the presence of low-energy collective spin-wave excitations. The emission and absorption of spin waves is accompanied by electronic spin flips. In our approximation the spin-wave bands narrow with increasing tempe rature leading eventually to an abrupt decrease of the spin magnetizat ion. We compare our results with recent magnetization data from NMR me asurements by Barrett et al.