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CuMnO2 nanoparticles with diameters of 64 nm were synthesized by a novel wet chemical method. An optimized two-step annealing method was developed through the analysis of thermogravimetric differential thermal analysis (TG-DTA) measurements in order to obtain single-phase CuMnO2. A sharp exothermic peak was observed in the DTA curve at approximately 500 K where structural changes of the copper oxides and manganese oxides in the precursor are expected to occur. It is believed that Cu+ ions were oxidized to Cu2+ ions and that Mn2+ ions were oxidized to Mn3+ ions in the Cu-Mn-O system. Deoxidization reactions were also found at approximately 1200 K. The optimized annealing temperature for the first step was determined to be 623 K in air. The optimized annealing temperature for the second step was 1173 K in an Ar atmosphere. Magnetization measurements suggested an antiferromagnetic spin ordering at approximately 50 K. It was expected that Mn3+ spin interactions induced magnetic phase transition affected by definite temperature.

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CoMn2O4 (cobalt manganite) nanoparticles encapsulated in amorphous SiO2 cages were prepared by a wet chemical method. Two different structures of CoMn2O4 nanoparticles, cubic and tetragonal, were observed in the X-ray diffraction patterns. CoMn2O4 crystals usually form a tetragonal structure with Jahn-Teller distortion, and the cubic structure is unstable. X-ray absorption fine structure (XAFS) measurements were performed on the obtained samples. From the X-ray absorption near-edge structure spectra of the Mn K-edge, it was concluded that Mn ions had a valence of 3+. This ion distribution of cobalt manganites should easily induce Jahn-Teller distortion. The magnetization of each particle was measured using a superconducting quantum interference device magnetometer, and obvious differences between cubic and distorted tetragonal structures were observed in the magnetization curve.