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          Institute: MPI für Chemische Physik fester Stoffe     Collection: publications 2013     Display Documents

ID: 670425.0, MPI für Chemische Physik fester Stoffe / publications 2013
Structural and Magnetic Phase Transitions in the AnBnO3n-2 Anion-Deficient Perovskites Pb2Ba2BiFe5O13 and Pb1.5Ba2.5Bi2Fe6O16
Authors:Abakumov, A. M.; Batuk, M.; Tsirlin, A. A.; Tyablikov, O. A.; Sheptyakov, D. V.; Filimonov, D. S.; Pokholok, K. V.; Zhidal, V. S.; Rozova, M. G.; Antipov, E. V.; Hadermann, J.; Van Tendeloo, G.
Date of Publication (YYYY-MM-DD):2013-07-15
Title of Journal:Inorganic Chemistry
Issue / Number:14
Start Page:7834
End Page:7843
Review Status:not specified
Audience:Not Specified
Abstract / Description:Novel anion-deficient perovskite-based ferrites Pb2Ba2BiFe5O13 and Pb1.5Ba2.5Bi2Fe6O16 were synthesized by solid-state reaction in air. Pb2Ba2BiFe5O13 and Pb1.5Ba2.5Bi2Fe6O16 belong to the perovskite-based A(n)B(n)O(3n-2) homologous series with n = 5 and 6, respectively, with a unit cell related to the perovskite subcell a(p) as a(p)root 2 x a(p) x na(p) root 2. Their structures are derived from the perovsldte one by slicing it with 1/2[110](p)((1) over bar 01)(p) crystallographic shear (CS) planes. The CS operation results in ((1) over bar 01)(p)-shaped perovsldte blocks with a thickness of (n - 2) FeO6 octahedra connected to each other through double chains of edge-sharing FeO5 distorted tetragonal pyramids which can adopt two distinct mirror-related configurations. Ordering of chains with a different configuration provides an extra level of structure complexity. Above T approximate to 750 K for Pb2Ba2BiFe5O13 and T approximate to 400 K for Pb1.5Ba2.5Bi2Fe6O16 the chains have a disordered arrangement. On cooling, a second-order structural phase transition to the ordered state occurs in both compounds. Symmetry changes upon phase transition are analyzed using a combination of superspace crystallography and group theory approach. Correlations between the chain ordering pattern and octahedral tilting in the perovskite blocks are discussed. Pb2Ba2BiFe5O13 and Pb1.5Ba2.5Bi2Fe6O16 undergo a transition into an antiferromagnetically (AFM) ordered state, which is characterized by a G-type AFM ordering of the Fe magnetic moments within the perovsldte blocks. The AFM perovsldte blocks are stacked along the CS planes producing alternating FM and AFM-aligned Fe-Fe pairs. In spite of the apparent frustration of the magnetic coupling between the perovskite blocks, all n = 4, 5, 6 A(n)Fe(n)O3(n-2) (A = Pb, Bi, Ba) feature robust antiferromagnetism with similar Neel temperatures of 623-632 K.
External Publication Status:published
Document Type:Article
Communicated by:Ina Werner
Affiliations:MPI für chemische Physik fester Stoffe
Identifiers:ISI:000322087100006 [ID No:1]
ISSN:0020-1669 [ID No:2]
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