Double perovskite Sr{sub 2}FeMoO{sub 6-x}N{sub x} (x=0.3, 1.0) oxynitrides with anionic ordering

Journal Article · Sun Jan 15 00:00:00 EST 2012 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.10.026· OSTI ID:21612844

Retuerto, M ^[1]; Calle, C de la; Martinez-Lope, M J ^[1]; Porcher, F ^[2]; Krezhov, K ^[3]; Menendez, N ^[4]; Alonso, J A ^[1]

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1. Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid (Spain)
2. Laboratoire Leon Brillouin, CEA/Saclay, 91191 Gif Sur Ivette Cedex (France)
3. Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee Boulevard, Sofia 1784 (Bulgaria)
4. Departamento de Quimica Fisica Aplicada, Facultad de Ciencias, Universidad Autonoma de Madrid, 28049 Madrid (Spain)

Two new oxynitride double perovskites of composition Sr{sub 2}FeMoO{sub 6-x}N{sub x} (x=0.3, 1.0) have been synthesized by annealing precursor powders obtained by citrate techniques in flowing ammonia at 750 Degree-Sign C and 650 Degree-Sign C, respectively. The polycrystalline samples have been characterized by chemical analysis, x-ray and neutron diffraction (NPD), Moessbauer spectroscopy and magnetic measurements. They exhibit a tetragonal structure with a=5.5959(1) A, c=7.9024(2) A, V=247.46(2) A{sup 3} for Sr{sub 2}FeMoO{sub 5.7}N{sub 0.3}; and a=5.6202(2) A, c=7.9102(4) A, V=249.85(2) A{sup 3} for Sr{sub 2}FeMoO{sub 5}N; space group I4/m, Z=2. The nitridation process seems to extraordinarily improve the long-range Fe/Mo ordering, achieving 95% at moderate temperatures of 750 Degree-Sign C. The analysis of high resolution NPD data, based on the contrast existing between the scattering lengths of O and N, shows that both atoms are located at (O,N)2 anion substructure corresponding to the basal ab plane of the perovskite structure, whereas the O1 site is fully occupied by oxygen atoms. The evolution of the Left-Pointing-Angle-Bracket Fe-O Right-Pointing-Angle-Bracket and Left-Pointing-Angle-Bracket Mo-O Right-Pointing-Angle-Bracket distances suggests a shift towards a configuration close to Fe{sup 4+}(3d{sup 4}, S=2):Mo{sup 5+}(4d{sup 1}, S=1/2). The magnetic susceptibility shows a ferrimagnetic transition with a reduced saturation magnetization compared to Sr{sub 2}FeMoO{sub 6}, due to the different nature of the magnetic double exchange interactions through Fe-N-Mo-N-Fe paths in contrast to the stronger Fe-O-Mo-O-Fe interactions. Also, the effect observed by low-temperature NPD seems to reduce the ordered Fe moments and enhance the Mo moments, in agreement with the evolution of the oxidation states, thus decreasing the saturation magnetization. - Graphical Abstract: We have synthesized and studied the new oxinitride double perovskites Sr{sub 2}FeMoO{sub 6-x}N{sub x}. They present anionic ordering between O and N. The nitridation process improves the long-range Fe/Mo ordering. They show a ferrimagnetic transition with a reduced saturation magnetization compared to Sr{sub 2}FeMoO{sub 6}, due to the different nature of the double exchange interactions through Fe-N-Mo-N-Fe in contrast to Fe-O-Mo-O-Fe. We suggest a shift towards a configuration Fe{sup 4+}(3d{sup 4}, S=2):Mo{sup 5+}(4d{sup 1}, S=1/2). Highlights: Black-Right-Pointing-Pointer Synthesis and study of the new oxinitride double perovskites Sr{sub 2}FeMoO{sub 6-x}N{sub x} (x=0.3, 1.0). Black-Right-Pointing-Pointer Compounds present anionic ordering between O and N. Black-Right-Pointing-Pointer Nitridation process extraordinarily improves the long-range Fe/Mo ordering. Black-Right-Pointing-Pointer We suggest a shift towards a configuration Fe{sup 4+}(3d{sup 4}, S=2):Mo{sup 5+}(4d{sup 1}, S=1/2).

• OSTI ID: 21612844
• Journal Information: Journal of Solid State Chemistry, Vol. 185; Other Information: DOI: 10.1016/j.jssc.2011.10.026; PII: S0022-4596(11)00568-8; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AMMONIA
AMMONOLYSIS
CHEMICAL ANALYSIS
CHEMICAL PREPARATION
EXCHANGE INTERACTIONS
FERRIMAGNETISM
MAGNETIC SUSCEPTIBILITY
MAGNETIZATION
MOESSBAUER EFFECT
NEUTRON DIFFRACTION
NITRIDATION
NITRIDES
PEROVSKITE
POLYCRYSTALS
SATURATION
SCATTERING LENGTHS
SPACE GROUPS
TETRAGONAL LATTICES
X-RAY DIFFRACTION
CHEMICAL REACTIONS
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
DECOMPOSITION
DIFFRACTION
DIMENSIONS
HYDRIDES
HYDROGEN COMPOUNDS
INTERACTIONS
LENGTH
MAGNETIC PROPERTIES
MAGNETISM
MINERALS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
OXIDE MINERALS
PEROVSKITES
PHYSICAL PROPERTIES
PNICTIDES
SCATTERING
SOLVOLYSIS
SYMMETRY GROUPS
SYNTHESIS