Nanoparticles of MnO with average diameters in the 6–14 nm range have been prepared by the decomposition of manganese cupferronate in the presence of TOPO, under solvothermal conditions. Nanoparticles of NiO with average diameters in the 3–24 nm range have been prepared by the decomposition of nickel cupferronate or acetate under solvothermal conditions. The nanoparticles have been characterized by X-ray diffraction and transmission electron microscopy. Both MnO and NiO nanoparticles exhibit supermagnetism, accompanied by magnetic hysteresis below the blocking temperature (TB). The TB increases with the increase in particle size in the case of NiO, and exhibits the reverse trend in the case of MnO.
