The magnetic structures of the mixed layer pnictide oxide compounds Sr2Mn3Pn2O2 (Pn = As, Sb)

Stephanie L. Brock, N. P. Raju, J. E. Greedan, Susan M. Kauzlarich

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31 Scopus citations

Abstract

Neutron powder diffraction results are reported for the compounds Sr2Mn3Pn2O2 (Pn = As, Sb), and the magnetic structures are determined. The chemical structure can be described as a 1:1 intergrowth of Mn2Pn2 2- layers of the BaAl4 type with MnO2 2- layers isostructural with the CuO2 planes found in cuprate superconductors. The Sr2+ cations separate the two layers. Two independent magnetic sublattices exist, Mn(1) and Mn(2), associated with the MnO2 2- and Mn2Pn2 2- layers respectively. Both sublattices have tetragonal symmetry, Mn(2) being primitive and Mn(1) being centered. The interlayer spacing within each sublattice is about 10 Å and between the sublattices it is about 5 Å. Owing to the centering of the Mn(1) sublattice, interactions between the nearest MnO2 2- layers cancel, as do interactions between the Mn(1) and Mn(2) sublattices. The Mn(2) sublattice is found to order at the relatively high temperatures of about 340 K (As) and 300 K (Sb) in a type Gz structure, k = (000) with a saturation moment of 3.4 μB at 4 K. At low temperatures new reflections of magnetic origin appear which can be assigned to the Mn(1) sublattice, but the details are different for each compound. The Mn(1) moments for Sr2Mn3Sb2O2 order below 65 K with k = (1/21/20) along 〈100〉, i.e. normal to the Mn(2) spins, with a significantly larger moment of 4.2 μB. In Sr2Mn3As2O2 one sees much weaker reflections below 75 K, the most prominent of which shows a Warren line shape characteristic of two-dimensional correlations only. Thus it appears that the Mn(1) sublattice may not order in the long range sense down to 4 K in Sr2Mn3As2O2. The properties of the individual sublattices of these manganese pnictide oxides are compared with similar magnetic sublattices of other compounds.

Original languageEnglish (US)
Pages (from-to)9-19
Number of pages11
JournalJournal of Alloys and Compounds
Volume237
Issue number1-2
StatePublished - Apr 15 1996

Keywords

  • Antiferromagnetism
  • Layered compounds
  • Magnetic structure
  • Neutron diffraction
  • Pnictide oxide compounds

ASJC Scopus subject areas

  • Metals and Alloys

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    Brock, S. L., Raju, N. P., Greedan, J. E., & Kauzlarich, S. M. (1996). The magnetic structures of the mixed layer pnictide oxide compounds Sr2Mn3Pn2O2 (Pn = As, Sb). Journal of Alloys and Compounds, 237(1-2), 9-19.