Itinerant electron ferromagnetism of a two dimensional system

A two-dimensional system, such as that found at the interface of a metal-oxide-semiconductor sandwich or on the surface of the liquid helium, is shown to be ferromagnetic for densities corresponding to r_s 10.8 within the ring diagram scheme at T = 0. The states of fractional, agnetization are not allowed for both the Coulomb and the zero-range interactions among the electrons. This system is shown to support spin waves. This should be compared with the Wigner crystallization of the system expected to occur for r_s? 9.