Ferromagnetism in partially spin-polarized GaInAs quantum wells

We performed measurements of the Shubnikov-de Haas effect (SdH) and of the Quantum-Hall effect (QHE) at GaInAs quantum wells confined by AlInAs barriers. At odd filling factors (1 and 3), the two-dimensional electron system (2DES) of the quantum well is partially spin-polarized, leading to an enhanced effective Landé factor g*. In this case, asymmetric and hysteretic SdH-oscillations were predicted. At filling factor 1 (higher spin polarization) the asymmetry could be confirmed experimentally. At filling factor 3, the predicted asymmetry could be observed at a sample of higher electron density in tilted magnetic fields above 12 T. A hysteresis was not resolvable due to a reduced spin polarization.