Spin-flip excitations from Landau levels in two dimensions

Dispersion relations for the spin-flip modes, in which an electron is both promoted from one Landau level to the next and its spin reversed, are calculated in the time-dependent Hartree-Fock approximation and in the generalized single-mode approximation for integer and noninteger filling factors. The energy of these modes can be shifted substantially by electron-electron interactions at k=0. This is in contrast to the magnetoplasma and spin-wave modes, which are not shifted at k=0. The calculated dispersion relations are compared with the results of recent inelastic light-scattering experiments near filling factor ν=1, and predictions are made for other filling factors.