First-Principles Study on Atomistic Behaviors and Magnetism of Physisorpted Co and Fe Atoms on MgO

Surface diffusion behaviors for Fe and Co adatoms on the MgO (001) surface were investigated using first-principles calculations. The potential energy calculations revealed that Fe and Co adatoms favored the on O site as initial adsorption site. The adsorption energies were calculated to be 1.97 and 0.73 eV for Fe and Co, respectively. Surface diffusion after the adsorption on O site was occurred by passing through the bridge site on the surface and energy barrier for the process was 0.54 eV for both adatoms. The magnetic moment of Co atoms on O site was 3.15 mu_B and the value was significantly reduced at the bridge site as 2.99 mu_B, while the corresponding value in vacuum state was 3.50 mu_B. Interestingly, the magnetic moment for Co adatom at the bridge site was increased by 0.08 mu_B compared to the case of adsorbed Co on O site. Spin polarization values for adatoms at the adsorption sites on the substrate were ranged from 82.9% to 100%