Spin polarization of strongly interacting two-dimensional electrons: The role of disorder

In high-mobility silicon metal-oxide-semiconductor field-effect transistors, the g*m* inferred indirectly from magnetoconductance and magnetoresistance measurements with the assumption that g*μBHₛ=2EF are in surprisingly good agreement with g*m* obtained by direct measurement of Shubnikov--de Haas oscillations. The enhanced susceptibility χ*∝(g*m*) exhibits critical behavior of the form χ*∝(n-n₀)^-α. We examine the significance of the field scale Hₛ derived from transport measurements, and show that this field signals the onset of full spin polarization only in the absence of disorder. Our results suggest that disorder becomes increasingly important as the electron density is reduced toward the transition.