Spin Transport and Localization in a Magnetic Two-Dimensional Electron Gas

Magnetotransport is investigated in a new class of heterostructures wherein a two-dimensional electron gas (2DEG) is exchange coupled to a 2D distribution of local moments. Quantum transport in these ``magnetic'' 2DEGs is strongly influenced by the s-d exchange-enhanced spin splitting, resulting in a highly spin polarized gas beginning at large Landau level filling factors. Diffusive transport in low magnetic fields is dominated by modifications of the Hartree corrections to the conductivity arising from the giant spin splitting. An anomalous negative magnetoresistance at higher magnetic fields suggests the suppression of spin-disorder scattering.