Giant magnetic anisotropy of single cobalt atoms and nanoparticles.
The isotropic magnetic moment of a free atom is shown to develop giant magnetic anisotropy energy due to symmetry reduction at an atomically ordered surface. Single cobalt atoms deposited onto platinum (111) are found to have a magnetic anisotropy energy of 9 millielectron volts per atom arising from the combination of unquenched orbital moments (1.1 Bohr magnetons) and strong spin-orbit coupling induced by the platinum substrate. By assembling cobalt nanoparticles containing up to 40 atoms, the magnetic anisotropy energy is further shown to be dependent on single-atom coordination changes. These results confirm theoretical predictions and are of fundamental value to understanding how magnetic anisotropy develops in finite-sized magnetic particles.
Gambardella
P
P
Institut de Physique des Nanostructures, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland. pietro.gambardella@epfl.ch
Rusponi
S
S
Veronese
M
M
Dhesi
S S
SS
Grazioli
C
C
Dallmeyer
A
A
Cabria
I
I
Zeller
R
R
Dederichs
P H
PH
Kern
K
K
Carbone
C
C
Brune
H
H