THERMODYNAMICS OF QUANTUM HALL FERROMAGNETS

The two-dimensional interacting electron gas at Landau level filling f actor nu = 1 and temperature T = 0 is a strong ferromagnet; all spins are completely aligned by arbitrarily weak Zeeman coupling. We report on its thermodynamic properties using a many-body perturbation theory approach and concentrating on the recently measured temperature depend ence of the spin magnetization. We discuss the interplay of collective and single-particle aspects of the physics and the opportunities for progress in our understanding of itinerant electron ferromagnetism pre sented by quantum Hall ferromagnets.