Crystal growth and characterization of cuprous ferrite (CuFeO2)

The growth of bulk cuprous ferrite (CuFeO2) single crystals by the travelling-solvent, floating-zone technique is reported. Crystals 5 to 8 mm in diameter by 10 to 30 mm have been grown from two sets of starting materials: Cu2O + Fe2O3 and 2CuO + Fe2O3, respectively. The trigonal unit-cell parameters determined by X-ray diffraction are a(h) = 3.035(1) Angstrom and c(h) = 17.161(4) Angstrom in the hexagonal description. Mossbauer studies reveal an isomer shift for Fe-57 at room temperature of 0.40 mm/s with respect to metallic iron, confirming that iron is in the trivalent state and that CuFeO2 is cuprous metaferrite (Cu+Fe3+O2). Magnetic susceptibility indicates that CuFeO2 undergoes two successive magnetic transition temperatures around T-N1 = 13.5 K and T-N2 = 9.5 K, respectively. Thermal analysis reveals that, under an argon atmosphere, CuFeO2 partially decomposes at 1180 degrees C to form Fe2O3 (or Fe3O4) and Cu2O.