2026-06-29T08:02:35Zhttps://docta.ucm.es/rest/oai/requestoai:docta.ucm.es:20.500.14352/425722023-08-28T19:14:48Zcom_20.500.14352_14col_20.500.14352_15
Variational mean-field approach to the double-exchange model
Alonso, J. L.
Fernández Pérez, Luis Antonio
Guinea, F.
Laliena, V.
Martín Mayor, Víctor
53
Spectral moments method
Diluted ising-model
Phase-separation
Colossal magnetoresistance
Ferromagnetic manganites
Manganese perovskites
Critical exponents
Electronic models
Doped manganies
Spin dynamics.
Física (Física)
Física-Modelos matemáticos
22 Física
© 2001 The 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 and V. S. Amaral. V.M.-M. was partially supported by MEC. We acknowledge financial support from Grant Nos. PB96-0875, AEN97-1680, AEN97- 1693, AEN97-1708, AEN99-0990 (MEC, Spain), and (07N/0045/98) (C. Madrid).
It has been recently shown that the double exchange Hamiltonian, with weak antiferromagnetic interactions, has a richer variety of first- and second-order transitions than previously anticipated, and that such transitions are consistent with the magnetic properties of manganites. Here we present a thorough discussion of the variational mean-field approach that leads to these results. We also show that the effect of the Berry phase turns out to be crucial to produce first-order paramagnetic-ferromagnetic transitions near half filling with transition temperatures compatible with the experimental situation. The computation relies on two crucial facts: the use of a mean-field ansatz that retains the complexity of a system of electrons with off-diagonal disorder, not fully taken into account by the mean-field techniques, and the small but significant antiferromagnetic superexchange interaction between the localized spins.
MEC
Comunidad de Madrid
Depto. de Física Teórica
Fac. de Ciencias Físicas
TRUE
pub
2023-06-20T00:26:34Z
2023-06-20T00:26:34Z
2011-02-01
journal article
https://hdl.handle.net/20.500.14352/42572
1098-0121
10.1103/PhysRevB.63.054411
eng
PB96-0875
AEN97-1680
AEN97- 1693
AEN97-1708
AEN99-0990
07N/0045/98
open access
application/pdf
American Physical Society