Spin polarization in a two-dimensional electron gas in GaAs

In this paper, positive magnetoresistance of a dilute two-dimensional electron gas in GaAs is studied in a parallel magnetic field B. It is found that the normalized resistivity curves, ρ(B)/ρ(0), merge together when we scale the field according to B/Bχ, where Bχ is assumed to be the field in which full spin polarization of electrons is reached. It is also shown that the crossing field, Bcross, determined by the crossover of the B2 dependence of the resistivity, becomes lower than Bχ with increasing electron density, which cannot be explained in terms of filling of the upper electron subbands in the fully spin-polarized regime. The spin susceptibility, χ, is assessed by extracting the product g*m*, where g* and m* are the effective Lande factor and electron mass, respectively. The behavior of χ with increasing electron density, however, deserves further theoretical and experimental study.