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Crystal Structure and Magnetism of the Double Perovskite Sr 3 Fe 2 MoO 9 :A Neutron Diffraction Study
Author(s) -
Viola María C.,
Alonso José A.,
Pedregosa José C.,
Carbonio Raul E.
Publication year - 2005
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200400746
Subject(s) - superexchange , chemistry , magnetism , antiferromagnetism , neutron diffraction , crystallography , tetragonal crystal system , perovskite (structure) , octahedron , crystal structure , ferromagnetism , magnetic structure , condensed matter physics , magnetization , physics , magnetic field , quantum mechanics
The Sr 3 Fe 2 MoO 9 double perovskite has been prepared in polycrystalline form by heat treatment, in air, from previously decomposed citrate precursors. This material has been studied by X‐ray (XRD), neutron powder diffraction (NPD) and magnetic measurements. At room temperature, the crystal structure is tetragonal, space group I 4/ m , with a = b = 5.5608(2) Å, c = 7.8471(4) Å. It is convenient to write the crystallographic formula as Sr 2 Fe(Fe 1/3 Mo 2/3 )O 6 , according to the usual nomenclature for double perovskites A 2 B'B''O 6 . The structure contains alternating FeO 6 and (Fe,Mo)O 6 octahedra, tilted by 3.9° in the basal ab plane. Magnetic measurements indicate a weak ferromagnetic behavior below T C = 280 K. Ideally, the Sr 3 Fe 2 MoO 9 double perovskite only contains Fe 3+ and Mo 6+ cations, in such a way that superexchange interactions between neighboring Fe 3+ spins are the only nominal mechanism accounting for the magnetism of this material. Our main finding is that this intrinsically “disordered” sample, containing a random distribution of Fe and Mo at the B'' positions, exhibits a strong magnetic scattering on the low‐angle Bragg positions, originating from naturally occurring groups of Fe 3+ cations in which strong antiferromagnetic (AFM) Fe–O–Fe superexchange interactions are promoted, similar to those existing in the LaFeO 3 perovskite. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)