Synthesis under high-oxygen pressure, magnetic and structural characterization from neutron powder diffraction data of YGa 1− xMn 1+ xO 5 ( x = 0.23): A comparison with YMn 2O 5

Abstract

A new material of nominal stoichiometry YGaMnO 5 has been prepared in polycrystalline form from citrate precursors followed by thermal treatments under high-oxygen pressure. This compound has been characterized from neutron powder diffraction (NPD) data and magnetic measurements. For comparison, the parent compound YMn 2O 5 has also been synthesized and its crystal structure refined by NPD data. The new oxide has an actual stoichiometry YGa 1− x Mn 1+ x O 5 ( x = 0.23), determined by NPD, showing an important cationic disorder between both metal sites; it is orthorhombic, Pbam (SG), and its crystal structure contains chains of Mn 4+O 6 edge-sharing octahedra, linked together by Ga 3+O 5 pyramids and YO 8 units. With respect to YMn 2O 5, containing axially elongated MnO 5 pyramids due to the Jahn–Teller effect of Mn 3+ cations, the GaO 5 pyramidal units in YGa 0.77Mn 1.23O 5 are substantially flattened. This compound has a paramagnetic behaviour with two weak anomalies at about 50 K and 350 K. The magnetic structures, studied at 1.4 K and 100 K show a ferromagnetic coupling along the chains of MnO 6 octahedra.