Modeling Ferro- and Antiferromagnetic Interactions in Metal鈥揙rganic Coordination Networks

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• 作者：Marisa N. Faraggi ; Vitaly N. Golovach ; Sebastian Stepanow ; Tzu-Chun Tseng ; Nasiba Abdurakhmanova ; Christopher Seiji Kley ; Alexander Langner ; Violetta Sessi ; Klaus Kern ; Andres Arnau
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：January 8, 2015
• 年：2015
• 卷：119
• 期：1
• 页码：547-555
• 全文大小：456K
• ISSN：1932-7455

文摘

Magnetization curves of two rectangular metal鈥搊rganic coordination networks formed by the organic ligand TCNQ (7,7,8,8-tetracyanoquinodimethane) and two different (Mn and Ni) 3d transition metal atoms [M(3d)] show marked differences that are explained using first-principles density functional theory and model calculations. We find that the existence of a weakly dispersive hybrid band with M(3d) and TCNQ character crossing the Fermi level is determinant for the appearance of ferromagnetic coupling between metal centers, as it is the case of the metallic system Ni-TCNQ but not of the insulating system Mn-TCNQ. The spin magnetic moment localized at the Ni atoms induces a significant spin polarization in the organic molecule; the corresponding spin density being delocalized along the whole system. The exchange interaction between localized spins at Ni centers and the itinerant spin density is ferromagnetic. On the basis of two different model Hamiltonians, we estimate the strength of exchange couplings between magnetic atoms for both Ni- and Mn-TCNQ networks that results in weak ferromagnetic and very weak antiferromagnetic correlations for Ni- and Mn-TCNQ networks, respectively.