کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1564263 | 999638 | 2006 | 5 صفحه PDF | دانلود رایگان |

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)∑iLˆiδ2, where Lˆiδ 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 Co7 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.
Journal: Computational Materials Science - Volume 35, Issue 3, March 2006, Pages 292–296