Magnetoresistance saturation in Si MOSFETs in a parallel pulsed magnetic field up to 40 T

The magnetoresistance of a two-dimensional electron gas in a disordered silicon (metal-oxide-semiconductor field-effect transistor) system in the presence of a parallel magnetic field was measured up to 40 T, which is a factor of $2$ larger than in previous measurements. We find resistance saturation for magnetic fields larger than the calculated magnetic field to completely spin polarize the electron gas. The magnetoresistance can be quantitatively described by screening and finite width effects in the spin-polarized electron gas. We estimate the number of local moments to be smaller than 0.65×10¹¹cm^-2.