Magnetism of Nanoporus Carbon with Manganese Clusters

Theoretical calculations of the electron density (taking into account the spin) of a model 16-atom carbon cluster with a manganese atom in a micropore showed that it is energetically favorable for manganese atoms to localize inside the pore and form metal nanoclusters in the carbon micropore. The magnetic moment of an ensemble of atoms surrounding a micropore with one manganese atom in it turned out to be quite large. An experimental method was proposed for introducing manganese clusters into bulk samples of nanoporous carbon with different porous structures, and the effect of these adsorbates on the magnetic properties of the samples was studied. In parallel, X-ray diffraction studies of the samples were carried out. It has been shown that Mn clusters near the surface are rather rapidly oxidized in air, as a result of which peaks associated with oxides predominate in the X-ray diffraction patterns. However, small Mn clusters have also been found. Measurements of the dependence of the magnetization of the samples on the applied field at T = 295 K showed the presence of nonlinearity and hysteresis characteristic of superparamagnetism or ferromagnetism.