Millimeter wave and DC investigations of spin effects in the 2DES of AlGaAs/GaAs

The spin properties of the 2DES in AlGaAs/GaAs heterostructures are studied via the electron spin resonance (ESR) of conduction electrons and via the temperature dependence of the DC-sigma (xx)(B) conductivity component. The ESR is investigated at integer (v = 1) and fractional filling factors (v < 1) via the change DeltaR(xx) of the magnetoresistance in high- and low-mobi lity samples. The DC-sigma (xx)(B) peaks in the integer quantum Hall effect regime show scaling behaviour. The peak widths obey power laws with expone nts of about 0.4 (strong spin splitting) and 0.2 (no spin splitting, one cr itical energy in the Landau level centre). By assuming two critical energie s in the latter case we obtain exponents close to 0.4. (C) 2001 Elsevier Sc ience B.V. All rights reserved.