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, rho(B)/rho(0), merge together when we scale the field according to B/B-chi, where B-chi is assumed to be the field in which full spin polarization of electrons is reached. It is also shown that the crossing field, B-cross, determined by the crossover of the B-2 dependence of the resistivity, becomes lower than B-chi 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, chi, is assessed by extracting the product g*m*, where g* and m* are the effective Lande factor and electron mass, respectively. The behavior of chi with increasing electron density, however, deserves further theoretical and experimental study.