Jahn-Teller, charge and magnetic ordering in half-doped manganese oxides

The phase diagram of half-doped manganite systems of formula A(0.5)A ' 0.5M nO3 is investigated within a single-orbital model incorporating magnetic do uble-exchange and superexchange, together with intersite, Coulomb and elect ron-lattice interactions. Strong Jahn-Teller and breathing mode deformation s compete together and result in shear lattice deformations. The latter sta bilize the charge-ordered CE-type phase, which undergo first-order transiti ons with temperature or magnetic field to either Ferromagnetic metallic or Paramagnetic insulating phases. An essential feature is the self-consistent screening of Coulomb and electron-phonon interactions in the ferromagnetic phase.