Preparation, structural and magnetic characterization of DyCrMnO5

The title compound has been first synthesized by a citrate technique followed by thermal treatments under moderate oxygen pressure conditions, and characterized by X-ray and neutron powder diffraction (NPD) and magnetization measurements. The crystal structure of DyCrMnO5 has been refined from NPD data in the space group Pbam; a=7.2617(6) Å, b=8.5161(6) Å, and c=5.7126(5) Å at 295 K. This oxide is isostructural with RMn2O5 oxides (R=rare earths) and it contains infinite chains of (Cr, Mn)4+O6 octahedra-sharing edges, linked together by (Mn, Cr)3+O5 pyramids and DyO8 units. The high degree of antisite disordering exhibited by DyCrMnO5 is noteworthy. The octahedral positions are occupied by roughly 50% of Mn and Cr cations, and the pyramidal groups contain two thirds of Mn and one third of Cr cations. We assume that Mn and Cr cations at the octahedral positions exhibit a tetravalent oxidation state, whereas the metals at the pyramidal positions are trivalent, in order to preserve the electroneutrality of this oxide. The susceptibility vs temperature curve of DyCrMnO5 does not suggest the establishment of a long-range magnetic structure even at low temperatures; the NPD technique does not provide any signal of magnetic ordering, since the reflections do not show any magnetic contribution.