Electron-spin resonance in the two-dimensional electron gas of GaAs-AlxGa1−xAs heterostructures

Abstract

Electron-spin resonance affects the magnetoresistivity of GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As heterostructures. With microwave frequencies of up to 70 GHz we studied systematically the spin splitting of the Landau levels in magnetic fields up to 14.5 T. The resonances within a certain Landau level are only observed at magnetic field values where the Fermi level is located between the corresponding spin levels. The spin splitting of a Landau level is an exact quadratic function of the magnetic field and its extrapolation to zero magnetic field leads to vanishing spin splitting. The g factors depend on the magnetic field and the Landau level index as follows: g(B,N)=${g}_{0}$-c(N+(1/2)B, where ${g}_{0}$ and c are sample-dependent constants.