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 I a 3 ̄ , with a = 9.89000 ( 3 ) Å for M=Mn and a = 10.07536 ( 4 ) Å 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 In2−sMsO3. 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 ≈ 95 K , with a very weak ferromagnetism effect at low temperatures.