Ferromagnetism in a quantum Hall system due to exchange enhancement in a GaInAs quantum well

We have investigated Ga0.47In0.53As/Al0.48In0.52As quantum well structures at magnetic fields close to the filling factor 1. At the critical current, a bistable and abrupt switching (transition width less than View the MathML source with respect to the filling factor) between quantum Hall conduction and dissipative conduction was observed at filling factors 1<ν<1.5. As confirmed by Hartree–Fock calculations, we attribute this switching to a feedback effect between the current-dependent population of different spin levels and the exchange-enhanced spin gap. The effect is accompanied by a ferromagnetic memory of the spin polarization when changing the external magnetic field.