Alonso, J. L.Fernández Pérez, Luis AntonioGuinea, FLaliena, V.Martín Mayor, Víctor2023-06-202023-06-202001-02-011098-012110.1103/PhysRevB.63.064416https://hdl.handle.net/20.500.14352/60058© 2001 American Physical Society. We are thankful for helpful conversations to L. Brey, J. Fontcuberta, G. Gómez-Santos, C. Simon, J. M. De Teresa, and especially to R. Ibarra. V.M.-M. acknowledges the financial support of MEC. The Monte Carlo simulations have been carried out in RTNN computers at Zaragoza and Madrid. We acknowledge financial support from Grant Nos. PB96-0875, AEN97-1680, AEN97-1693, AEN99-0990 (MEC, Spain), and (07N/0045/98) (C. Madrid).It is shown that the double-exchange Hamiltonian, with weak antiferromagnetic interactions, has a rich variety of first-order transitions between phases with different electronic densities and/or magnetizations. The paramagnetic-ferromagnetic transition moves towards lower temperatures, and becomes discontinuous as the relative strength of the double-exchange mechanism and antiferromagnetic coupling is changed. This trend is consistent with the observed differences between compounds with the same nominal doping, such as La_(2/3)Sr_(1/3)MnO_(3) and La_(2/3)Ca_(1/3)MnO_(3). Our results suggest that, in the low doping regime, a simple magnetic mechanism suffices to explain the main features of the phase diagram.engjournal articlehttp://doi.org/10.1103/PhysRevB.63.064416http://journals.aps.org/open access53Inelastic-neutron-scatteringMetal-insulator-transitionMixed-valence manganitesSpectral moments methodcolossal-magnetoresistancePhase-separationManganese perovskitesSpin dynamicsFerromagnetic manganitesCharge localization.Física (Física)Física-Modelos matemáticos22 Física