Tight-binding study of the CO chemisorption effect on cobalt magnetization

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.

Synthesis and self-assembly of monodisperse CoxNi100−x (x=50,80) colloidal nanoparticles by homogenous nucleation

“…The core-shell model [41] has been reported to explain such type of behavior in case of metal and metal alloy nanoparticles. Besides this, chemisorption of surfactants on the surface of CoNi nanoparticles [17] may be another possible reason for decrease in saturation magnetization as compared to its bulk value. Fig.…”

“…Many interesting magnetic properties are exhibited by these nanoparticles compared to their bulk counterparts [6][7][8]. The magnetic properties of alloy nanoparticles depend on various factors such as size [6,9], shape [10], anisotropy [11][12][13], surface effects [6,13], crystal structure [1,13], composition [1,14,15], adsorption of surfactants [16,17] and magnetic interaction between particles [18,19]. Below certain critical size, non-interacting single domain magnetic nanoparticles exhibit superparamagnetism, i.e.…”

Controlled metal nanostructures: Fertile ground for coordination chemists

“…This can be attributed to adventitious oxygen adsorption and surface oxidation in some cases, but most of the time the electronic effects of M a n u s c r i p t 51 other coordinated ligands have to be considered. Theoretical calculations predict that chemisorption of CO on Co or Ni nanoparticles induces a drastic reduction of their surface atoms magnetic moment [299], [300], [301], while only a neglectable effect is expected from coordination of NH3 on the same clusters [302]. Studying this effect experimentally is far from simple as it demands a very strict control over the composition and surface chemistry of the NPs.…”

Density-functional study of the CO adsorption on ferromagnetic Co(0001) and Co(111) surfaces

“…Strange enough, however, theoretical analysis of the effect of the CO molecule upon magnetic properties of Co surfaces on the first-principle level is completely lacking. It was performed [28] only at the semi-empirical level for atop and bridge CO positions above Co(0 0 0 1) in not optimized geometries. The calculation predicts that CO molecule adsorbed at atop position drastically reduces magnetic moment of its Co nearest-neighbour, whereas the effect is very small for adsorption in the bridge position.…”