Title
A vacancy-disordered, oxygen-deficient perovskite with long-range magnetic ordering : local and average structures and magnetic properties of <tex>$Sr_{2}Fe_{1.5}Cr_{0.5}O_{5}$</tex>
Author
Faculty/Department
Faculty of Sciences. Physics
Publication type
article
Publication
Easton, Pa ,
Subject
Physics
Chemistry
Source (journal)
Inorganic chemistry / American Chemical Society. - Easton, Pa
Volume/pages
51(2012) :4 , p. 2638-2644
ISSN
0020-1669
ISI
000300466300079
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
The local and average crystal structures and magnetic properties of the oxygen-deficient perovskite Sr2Fe1.5Cr0.5O5+y were studied using powder X-ray and neutron diffraction, neutron-pair distribution function analysis, and electron energy-loss spectroscopy. This material crystallizes in the cubic Pm3&#773;m space group, with a = 3.94491(14) Å. The oxygen vacancies are distributed randomly throughout the perovskite-type structure, and the average coordination number of the Fe(Cr) sites is 5. Refinement of the neutron diffraction data indicates y 0.05. This is in discordance with an earlier report on a material with the same nominal composition and cell constant. Electron energy-loss Cr L2,3-edge spectroscopy shows that Cr3+ is present, which is also contrary to previous speculation. Neutron-pair distribution function studies show that a brownmillerite-like model involving ordered vacancies and alternating octahedral and tetrahedral coordination at the metal sites, gives a better description of the local structure out to 5 Å. A remarkable phenomenon determined by neutron diffraction in Sr2Fe1.5Cr0.5O5 is the occurrence of a long-range G-type antiferromagnetic ordering with Tc ≈ 565 K because cubic oxygen-deficient perovskites with B-site disorder usually do not undergo transitions to magnetically ordered states. The observation of long-range antiferromagnetic order and the Tc value are in accordance with previous Mössbauer spectroscopic studies.
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