J. Phys. Soc. Jpn. 77, 014301 (2008) [9 Pages]

Theoretical Analysis of Magnetic Coupling in Sandwich Clusters Vn(C6H6)n+1

+ Affiliations
1Research Center for Integrated Science, Japan Advanced Institute of Science and Technology, Nomi, Ishikawa 923-12922Creative Research Initiative “Sousei”, Hokkaido University, Sapporo 001-00213Research Institute for Computational Sciences, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568

The mechanism of ferromagnetism stability in sandwich clusters V n (C 6 H 6 ) n +1 has been studied by first-principles calculation and model analysis. It is found that each of the three types of bonds between V and benzene (Bz) plays different roles. V 3d z 2 orbital, extending along the molecular axis, is weakly hybridized with Bz's HOMO-1 orbital to form the σ-bond. It is quite localized and singly occupied, which contributes 1 µ B to the magnetic moment but little to the magnetic coupling between neighboring V magnetic moments. The in-plane d x 2 - y 2 , d x y orbitals are hybridized with the LUMO of Bz and constitute the δ-bond. This hybridization is medium and crucial to the magnetic coupling though the δ states have no net contribution to the total magnetic moment. d x z , d y z , and HOMO of Bz form a quite strong π-bond to hold the molecular structure but they are inactive in magnetism because their energy levels are far away from the Fermi level. Based on the results of first-principles calculation, we point out that the ferromagnetism stability is closely related with the mechanism proposed by Kanamori and Terakura [J. Phys. Soc. Jpn. 70 (2001) 1433]. However, the presence of edge Bzs in the cluster introduces an important modification and suppresses significantly the ferromagnetism stability. A simple model is constructed to explain the essence of the physical picture.

©2008 The Physical Society of Japan


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