Diagrammatic method for theory of magnetic and resistive properties of   manganites
  Effective field theory of magnetic and resistive properties of manganites with account of strong Hund exchange coupling and electron-phonon interactions has been evolved under the strong Hund coupling condition. In parallel with Lang-Firsov unitary transformation of the zeroth Hamiltonian, we have realized the diagonalization of Hund's Hamiltonian neglecting the upper triplet. The diagram techniques taking into account the quantum spin fluctuations of lower quintet and hole state with spin S=3/2 was developed. The magnetic structure of the ground state and an influence of electron-phonon interaction have been analyzed using the first nonvanishing approximation of perturbation theory. The calculated temperature dependence of resistivity agrees well with experimental data including these obtained in applied magnetic field. 
E.E. Zubov and V.P. Dyakonov