Ip. Smorchkova et al., GIANT MAGNETORESISTANCE AND QUANTUM PHASE-TRANSITIONS IN STRONGLY LOCALIZED MAGNETIC 2-DIMENSIONAL ELECTRON GASES, Physical review. B, Condensed matter, 58(8), 1998, pp. 4238-4241
The application of a small magnetic field (B approximate to 0.1T) eith
er parallel or perpendicular to a low-density (approximate to 10(11) c
m(-2)) magnetic two-dimensional electron gas (2DEG) creates a striking
positive magnetoresistance of up to 700%. This is a spin effect, caus
ed by the suppression of spin-dependent hopping paths between localize
d states with on-site correlation. At higher fields, a spin-related de
localization is observed. In the perpendicular field geometry, orbital
effects combine with this delocalization and lead to quantum phase tr
ansitions between the spin-polarized insulating state and the nu=1 qua
ntum Hall liquid.