RT Journal Article T1 Discontinuous transitions in double-exchange materials A1 Alonso, J. L. A1 Fernández Pérez, Luis Antonio A1 Guinea, F A1 Laliena, V. A1 Martín Mayor, Víctor AB 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. PB American Physical Society SN 1098-0121 YR 2001 FD 2001-02-01 LK https://hdl.handle.net/20.500.14352/60058 UL https://hdl.handle.net/20.500.14352/60058 LA eng NO © 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). NO MEC, Spain NO C. Madrid, Spain DS Docta Complutense RD 21 abr 2025