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Electronic properties of double perovskite compounds
Author(s) -
Carvajal E.,
Navarro O.,
Allub R.,
Avig M.,
Alascio B.
Publication year - 2005
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200461726
Subject(s) - superexchange , antiferromagnetism , condensed matter physics , spins , ferromagnetism , electron localization function , curie temperature , electronic structure , electron , ground state , metal , materials science , electronic band structure , chemistry , physics , atomic physics , quantum mechanics , metallurgy
The double perovskites family A 2 MM′O 6 (A being an alkaline‐earth and M, M′ two different transition‐metal 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 2 FeMoO 6 and Sr 2 FeReO 6 are half‐metallic ferromagnets with fairly large T c (≈450 K) while Sr 2 FeWO 6 is known as an antiferromagnetic insulator with T N ≈ 37 K. As expected, a metal–insulator and magnetic transition has been reported in the substituted compounds Sr 2 FeMo x W 1– x O 6 . To elucidate the origin of such different behavior in these Sr 2 FeMO 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 double‐exchange type interaction taking place in the hybridized Fe–M t 2 g 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 in the substituted compounds like Sr 2 FeMo x W 1– x O 6 , when disorder among Mo/W takes place in the M‐sublattice. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)