Ab Initio Study on Nitrogen or Carbon Doped Magnesium Oxide

The ferromagnetism induced by nitrogen (N) or carbon (C) atoms in magnesium oxide (MgO) is studied by using ab initio calculation based on the density functional theory. The calculation shows that single N or C impurity may induce local magnetic moment to MgO due to the localization of p-electrons. Moreover, the calculation of two impurities in one supercell shows that the stability of ferromagnetism in both N:MgO and C:MgO depends on the distance between the two impurities. The energy difference between the ferromagnetic and antiferromagnetic states in some situations is smaller than 28 meV, the thermal energy at room temperature, suggesting that both the localization of the p-electrons and the distance between the impurities may influence the stability of ferromagnetism.