Structure and magnetic properties of In 2RuMnO 6 and In 2RuFeO 6 : Heavily transition-metal doped In 2O 3 -type bixbyites

Abstract

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-M 2O 3 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 In 2O 3 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− s M s O 3. Here, we describe a substantial incorporation of magnetic transition metals into In 2O 3 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 Ru 3+/M 3+↔Ru 4+/M 2+. In 2RuFeO 6 shows antiferromagnetic interactions below T N ≈ 95 K , with a very weak ferromagnetism effect at low temperatures.