Electronic properties of double perovskite compounds
Por:
Carvajal E., Navarro O., Allub R., Avignon M., Alascio B.
Publicada:
1 ene 2005
Resumen:
The double perovskites family A 2MM'O 6 (A being an alkaline-earth and M, M' two different transitionmetal elements) is considered as a serious candidate for magnetoelectronic applications. It appears to be fundamental to understand the role of electronic parameters controlling the half-metallic ground state and high Curie temperature T c. In this respect it is very interesting that different members of the family present a variety of electronic and magnetic properties. Among them, Sr 2FeMoO 6 and Sr 2FeReO 6 are halfmetallic ferromagnets with fairly large T c(?450 K) while Sr 2FeWO 6 is known as an antiferromagnetic insulator with T n*ap;37 K. As expected, a metal-insulator and magnetic transition has been reported in the substituted compounds Sr2FeMo^W,_XO6. To elucidate the origin of such different behavior in these Sr 2FeMO 6 double perovskites we consider a correlated electron picture with localized Fe-spins (d 5 configuration) and conduction electrons originating from M (M = Mo, Re or W) together with the doubleexchange type interaction taking place in the hybridized Fe-M t 2g band and competing with the antiferromagnetic superexchange interactions between the Fe-spins. We consider here only the ordered stucture in which Fe and M constitute two interpenetrating sublattices. Using a tight-binding model and the renormalized perturbation expansion technique, we calculate the density of states and determine the behaviour of the critical temperature as a function of the band filling and the Fe-M charge transfer energy. This allows us to discuss the stability of the half-metallic ferromagnetic state with increasing charge transfer energy. We will also discuss the electronic properties and the ferro-antiferromagnetic transition hi the substituted compounds like Sr 2FeMo xW 1-xO 6, when disorder among Mo/W takes place in the M- sublattice. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Filiaciones:
Carvajal E.:
Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, 04510, México, D. F., Mexico
Navarro O.:
Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, 04510, México, D. F., Mexico
Allub R.:
Instituto Balseiro, Centro Atómico Bariloche, 8400 San Carlos de Bariloche, Argentina
Avignon M.:
Laboratoire d'Études des Propriétés Électroniques des Solides, CNRS, BP 166, 38042 Grenoble, France
Alascio B.:
Instituto Balseiro, Centro Atómico Bariloche, 8400 San Carlos de Bariloche, Argentina
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