Structure and magnetic properties of In2RuMnO6 and In2RuFeO6 : Heavily transition-metal doped In2O3 -type bixbyites

The title compounds have been synthesized by a citrate technique. The crystal structure of these materials has been studied at room temperature from high-resolution neutron powder diffraction data. In, Ru, and M=Mn,Fe are distributed at random over the metal sites of a C-M₂O₃ bixbyite-type structure, space group $Ia\stackrel{?}{3}$, with $a=9.89000\left(3\right)\AA$ for M=Mn and $a=10.07536\left(4\right)\AA$ for M=Fe. It is well known that In₂O₃ is able to dissolve certain amounts of transition metals but, at ambient pressure, the solubility is rather small, lower than $s=0.5$ in In_2?sM_sO₃. Here, we describe a substantial incorporation of magnetic transition metals into In₂O₃ of half of the metal positions ($s=1$), by simple thermal treatment at temperatures in the 1300–1400 °C range. Although a bond-valence study shows unrealistically low valences for Ru ions, which statistically occupy the metal positions, replacing In, the magnetic properties suggest a valence equilibrium Ru³⁺/M³⁺?Ru⁴⁺/M²⁺. In₂RuFeO₆ shows antiferromagnetic interactions below $T_N\approx 95K$, with a very weak ferromagnetism effect at low temperatures.