Crystal and Magnetic Study of the Disordered Perovskites Ca(Mn0.5Sb0.5)O3 and Ca(Fe0.5Sb0.5)O3 Articles uri icon

authors

publication date

  • October 2010

start page

  • 1449

end page

  • 1454

issue

  • 10

volume

  • 45

International Standard Serial Number (ISSN)

  • 0025-5408

abstract

  • We have investigated the double perovskites Ca 2 MSbO 6 (M= Mn, Fe) that have been prepared by solid-state reaction (M= Fe) and wet chemistry procedures (M= Mn). The crystal and magnetic structures have been
    studied from X-ray (XRD) and neutron powder diffraction (NPD) data.
    Rietveld refinements show that the crystal structures are orthorhombic
    (space group Pbnm ) with complete disorder of M and Sb cations, so the
    formula should be rewritten as Ca(M 0.5 Sb 0.5 )O 3 . Due to this
    disorder no evidences of Jahn-Teller distortion can be observed in the
    MnO 6 octahedra of Ca(Mn 0.5 Sb 0.5 )O 3 , in contrast with the ordered
    double perovskite Sr 2 MnSbO 6 . Ca(Fe 0.5 Sb 0.5 )O 3 behaves as an
    antiferromagnet with an ordered magnetic moment for Fe 3+ of 1.53(4) mu B
    and a propagation vector k = 0, as investigated by low-temperature NPD.
    The antiferromagnetic ordering is a result of the high degree of Fe/Sb
    antisite disorder of the sample, which originates the spontaneous
    formation of Fe-rich islands, characterized by the presence of strong
    Fe-O-Fe antiferromagnetic couplings with enough long-range coherence to
    produce a magnetic contribution perceptible by NPD. By contrast, the
    magnetic structure of Ca(Mn 0.5 Sb 0.5 )O 3 cannot be observed by
    low-temperature NPD because the magnitude of the ordered magnetic
    moments is below the detection threshold for neutrons.