No abstract

Performing ab initio and tight-binding calculations we demonstrate the effect of atomic relaxations on the magnetic properties of Co adatoms and Co clusters on the Cu͑001͒ surface. Atomic relaxations decrease the spin and orbital magnetic moments and drastically affect the magnetic anisotropy of the Co adatom. We show that due to relaxations the in-plane magnetization of the Co adatom is stabilized.

No abstract

The interplay between structure and magnetic properties of small cobalt clusters embedded in a Cu(001) surface is studied performing ab initio and tight-binding calculations in a fully relaxed geometry. We reveal that, despite the small macroscopic mismatch between Co and Cu, the strain relaxations at the interface have a profound effect on the structure of the clusters and the substrate. The physical mechanism responsible for the strain relaxations in embedded clusters is related to the size-dependent mesoscopic mismatch which has been recently introduced to understand homo-and heteroepitaxial growth at the mesoscale [O. V. Lysenko et al., Phys. Rev. Lett. 89, 126102 (2002)]. We show that the atomic relaxations strongly reduce the magnetic anisotropy energy (MAE) and the orbital magnetic moments of embedded clusters. The largest MAE of about 1.8 meV is found for a single Co atom in the Cu(001) surface. A strong enhancement of the spin magnetic moments in embedded clusters as compared to a single atom of Co incorporated in the Cu(001) surface is found. Magnetic properties of embedded and supported clusters are compared. While in supported clusters the MAE is strongly enhanced at the edge atoms, the immersion of the cluster into the surface and atomic relaxations make the distribution of the local MAE contributions and orbital-moment values almost homogeneous.

No abstract

No abstract

No abstract

By using a semiempirical self-consistent tight-binding scheme we study the effect of O and CO chemisorption on the Co͑0001͒ surface magnetization. Similar calculations are performed for the Co 13 and Co 55 clusters of high symmetry. The CO molecule in the atop position, but not in the bridge geometry, is effective in local magnetization quenching. In clusters magnetic phase transitions are observed as the Co-CO separation varies. When the separation is more than about 1.8 Å, the Co magnetization remains strong. The character of phase transitions conforms to the formal predictions based on the Landau theory.