Electron-phonon interaction in ferromagnetic semiconducting thin films

The effect of electron-phonon interaction on the temperature dependence of the electronic spectrum in thin ferromagnetic semiconducting films is studied using the s-d interaction model and a Green function formalism beyond the random phase approximation. We obtain three temperature regions with different contributions of the damping terms due to the s-d, electron-electron and electron-phonon interactions. The phonon spectrum is discussed, too. Additional phonon damping and phonon frequency shift arise when the electron-phonon interaction is properly included. The phonon linewidth may be obtained from the cubic terms of the anharmonic phonon-phonon interaction, while the calculation of the renormalized phonon frequency of the experimentally obtained frequency shift required inclusion of the quartic term in the anharmonic interaction. The frequencies in thin ferromagnetic semiconducting films are smaller and the damping effects larger in comparison with the bulk case