Narrow Results

In this paper, α-Mn₂O₃ thin films were fabricated by plasma-assisted molecular beam epitaxy on SrTiO₃ and Nb:SrTiO₃, respectively. The grown samples showed room temperature ferromagnetism (RFM) properties. All the experimental results manifested that the RFM properties in undoped thin films were induced by oxygen vacancies formed during the growth process. Even more, the ferromagnetism of thin films grown on Nb:SrTiO₃ were enhanced, and these results confirmed the fact that oxygen vacancies induced ferromagnetism. That is to say, more oxygen vacancies result the more unpaired electrons induced prominent abnormal spin causing ferromagnetism.

Mn K-edge absorption measurements were carried out on α-Mn₂O₃ and Mn₃O₄ nanocrystals supported on a mesoporous silica, SBA-15. The X-ray absorption near edge structure (XANES) spectra demonstrate the existence of the oxidation states of Mn (2+ and 3+) in Mn₃O₄ and Mn (3+) in Mn₂O₃, those ions were present in different octahedral environments. Meanwhile, XANES data demonstrate that some Mn atoms that are bonding to the inner wall of the channels as isolated species, may exist as Mn⁴⁺ in Mn₂O₃/SBA-15. In addition, the structure, texture, and electronic properties of nanocomposites were also studied using various characterization techniques including X-ray diffraction (XRD) and laser Raman spectroscopy (LRS). The formation of the hausmannite Mn₃O₄ and bixbyite Mn₂O₃ structures has been confirmed clearly by XRD. The prepared nanocomposites of MnO_x showed significant catalytic activity towards CO oxidation below 523 K.