The Electron Spin Resonance of the Mn2+ Ion on the Surface of Magnesium Oxide

The behavior of the Mn2+ ion on the surface of MgO was studied by using the ESR technique. The powder of MgO, the surface of which was doped with the Mn2+ ion, was calcined at different temperatures from 100 to 1000°C in a vacuum, and then the ESR spectra were observed at room temperature. It was noticed that the spectral intensity showed a minimum at about 500°C, that the zero-field splitting parameter, D, increased with the temperature, and that the hyperfine coupling constant, A, decreased enormously at about 700°C. The environments around the Mn2+ ion on the surface of MgO were discussed on the basis of these results. When H2, CO, or O2 was added after the calcination, the D and A values changed in the temperature range above 500°C. Especially when O2 was introduced, the D value fell to zero upon treatment at 1000°C. The crystal field around the Mn2+ ion and the bonding between the Mn2+ ion and its environments were discussed by taking into account the results of the magnetic-susceptibility measurements of the manganese ion on MgO.