We use the first principles RS-LMTO-ASA (Real Space - Linear Muffin-Tin Orbital - Atomic Sphere
Approximation) method, based on the Density Functional Theory and implemented to calculate noncollinear
magnetic structures, to investigate the magnetic properties of nanostructures adsorbed on
metallic surfaces. We have considered different geometries and sizes such as adatoms, dimers, trimers,
nanowires, and nanostructures with triangular geometry of Fe, Fe-Co and Fe-Pt on Pt(111), as well as
Mn nanostructures on Ag(111) surface. The Fe-Co nanowires adsorbed on Pt(111) are found to order ferromagnetically
regardless of the nanowire size. We find enhanced spin and orbital moments at Fe and Co
sites compared to what is found in bulk, which is attributed to the reduced coordination number presented
at the surface. We also analyzed how these moments vary as a function of the concentration of these
elements at the nanowires. For systems composed by Fe-Pt nanowires adsorbed on Pt(111), our results
show that it is possible to tune the exchange interaction between magnetic adatoms (Fe) by introducing
a different number of Pt atoms to link them. For instance, the exchange interaction between Fe adatoms
can be considerably increased by introducing Pt chains to link them. Moreover, either a ferromagnetic
or an antiferromagnetic configuration between magnetic adatoms (Fe) can be stabilized depending on
the Pt spacer thickness. Furthermore, even a non-collinear magnetic ordering can be obtained tuned by
Pt-mediated atoms. For Mn clusters on Ag(111), the exchange interactions between Mn sites depend not
only on the distance between the atoms, but also on the coordination number of each site. Therefore, the
non-collinear ordering in these nanostructures is caused not only if antiferromagnetism is frustrated by
the cluster geometry, but also by the competition between short and long range exchange interactions.
The results obtained are in general in good agreement with experiment and other calculations, when
available in the literature.
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