ITINERANT-ELECTRON MAGNETISM IN THE QUANTUM HALL REGIME

The two-dimensional interacting electron gas at Landau level filling factor v = 1 at temperature T = 0 is a strong ferromagnet; all spins are 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 obtained 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 temperature leading eventually to an abrupt decrease of the spin magnetization. We compare our results with recent magnetization data from NMR measurements by Barrett et al.