Magnetization instabilities at tilted magnetic fields in the quantum Hall regime

In high-mobility samples, we show that a magnetization instability occurs at filling factor ν=2 in the quantum-Hall-effect regime under the application of a parallel magnetic field. The instability is caused by feedback from the screened exchange energy of the electrons. We perform calculations on ${\mathrm{Ga}}_{\mathit{x}}$ ${\mathrm{In}}_{1\mathrm{-}\mathit{x}}$As-InP heterostructures and show that a surprising jump in the magnetization occurs at experimentally accessible magnetic fields and sample mobilities. This phenomenon is experimentally observable and possible experiments are proposed.