Local magnetic properties and electronic structures of 3d and 4d impurities in Cu clusters.

Abstract

The local magnetic properties and electronic structures of ${\mathrm{Cu}}_{12}$R clusters with ${\mathit{I}}_{\mathit{h}}$ and ${\mathit{O}}_{\mathit{h}}$ symmetries (R=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, and Ag) have been systematically studied with the density-functional formalism, and the Kohn-Sham equation is solved self-consistently with the discrete variational method. By calculating the binding energies for 3d series, we find that the icosahedral structure is more stable than the octahedron structure. Pd and Ag doping can enhance the stability of a cluster, and the alloying effects in such doped clusters have an important effect on binding energy. The electronic structures calculated in equilibrium configurations show that the clusters with R=Cu, Cr, Mo, or Ag have closed electronic shells, while the others have open electronic shells. In particular, we have performed comprehensive calculations on the local magnetism of impurities in a cluster, and found that the behavior of local magnetism for 3d and 4d impurities in ${\mathrm{Cu}}_{12}$ clusters is different from that in bulk as well as from that in ${\mathrm{Al}}_{12}$ clusters. In contrast to the d-d interaction picture for local magnetism in the d-band bulk host, we have found that there are more complicated interactions acting in clusters to affect the local magnetism of impurities: the interactions of the Cu-p orbital with R-spd orbitals play a crucial role on the local magnetic moment for impurities with more than a half-filled d shell, such as Mn, Fe, Co, Ni, Tc, Ru, and Rh; the interactions of the Cu-d orbital with R-spd orbitals contribute to the local magnetic moment for impurites with a less than half-filled d shell, such as Sc, Ti, V, Y, Zr, and Nb. We have also tested and discussed the Stoner-like criterion for the occurrence of a local moment in a cluster. \textcopyright{} 1996 The American Physical Society.