Coherent Spin Dynamics of a Two-Dimensional Electron Gas in the Mode of a Hall Ferromagnet

The spin-depolarized electron system in a GaAs quantum well at the filling factor ν = 1 is investigated using the time-resolved Kerr rotation technique. At temperatures above 5 K, a transition from the new spin-correlated state to a state with a low spin stiffness characteristic of a single-particle electron system is observed. A nonlinear contribution to the damping of Larmor oscillations that is manifested at low temperatures, when spin-spin correlations determine the ground state of the two-dimensional electron system, is identified. The parameters of the fluctuating magnetic field acting on individual electron spins are estimated.