Fabrication and abnormal magnetic properties of MnO nanoparticles via vapor phase growth

Nano-sized MnO particles were synthesized via vapor phase deposition on silicon substrates. The products were characterized by X-ray diffraction and transmission electron microscopy. The results reveal that the MnO nanoparticles are sphere like and well crystallized with diameters less than 40 nm. Magnetization measurements show that the MnO nanoparticles exhibit obvious ferromagnetic behavior with a ferromagnetic to paramagnetic phase transition at 42 K. A large coercivity of up to 4035 Oe and a remanence of 0.646 (emu g(-1)) have been observed at 5 K. The ferromagnetic behavior of these MnO nanoparticles can be explained in terms of the presence of non-compensated surface spins on the antiferromagnetic core due to the high surface-to-volume ratio. (c) 2005 Elsevier B.V. All rights reserved.