Coherent spin dynamics of a two-dimensional electron gas in the mode of a Hall ferromagnet

By means of the time-resolved Kerr rotation technique, a spin-depolarized electron system at a filling factor $\nu$ = 1 in a GaAs quantum well was studied. At temperatures above 5 K, a transition from a new spin-correlated state to a state with low spin stiffness characteristic of a single-particle electron system was found. A nonlinear contribution to the decay of Larmor oscillations arising at low temperatures, when spin-spin correlations determine the ground state of a two-dimensional electron system, is highlighted. The parameters of the fluctuating magnetic field acting on individual electron spins are estimated.