Calculation of orbital polarization effects in small Co clusters Conference Paper uri icon

abstract

  • The effects of orbital polarizations on the magnetic properties of small Co clusters are investigated in the framework of a self-consistent electronic model Hamiltonian including local Coulomb interactions at three different levels of approximation: (i) full orbital dependence of the direct and exchange Coulomb interactions Umm′ and Jmm′ as given by atomic symmetry, (ii) orbital-independent interactions U=Umm′andJ= Jmm′, and (iii) orbital polarization (OP) approximation of the form HOP=-(B/2)∑iL̂iδ2, where L̂iδ refers to the orbital momentum operator at atom i and B to the Racah coefficient. Results are given for the orbital magnetic moments 〈Lδ〉 along high-symmetry magnetization directions δ and for the corresponding magnetic anisotropy energy ΔE. A compact five-fold symmetric Co 7 cluster is considered as representative example. It is shown that with an appropriate choice of B the OP approximation yields a very good agreement with the rigorous orbital-dependent calculations. Moreover, one observes that the orbital-independent approach accounts qualitatively for the main general trends in 〈Lδ〉 and MAE. Advantages and limitations of the various approaches are discussed. © 2005 Elsevier B.V. All rights reserved.

publication date

  • 2006-01-01