Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5420067 | Progress in Surface Science | 2009 | 12 Pages |
Abstract
We have investigated computationally the magnetic spin state of free metalloporphyrins and how magnetic ordering in metalloporphyrins can be induced through contact with the metallic surface and what the origin of the exchange interaction is. To this end, we performed density functional theory (DFT) and DFTÂ +Â U studies for a series of isolated, ligated as well as unligated Fe-porphyrin (FeP) molecules as well as various FeP molecules on surfaces. Our calculations for isolated FePs clearly demonstrate that the usual DFT-based exchange-correlation functionals (such as the generalized gradient approximation) cannot predict the experimental high-spin ground state of these molecules. Instead, one has to resort to DFTÂ +Â U calculations with a Coulomb U of about 4Â eV on the Fe atoms, to obtain the correct single-molecule spin state. The magnetic interaction between FeP and a Co surface has been studied computationally with the DFT and DFTÂ +Â U approaches. Our total energy DFT and DFTÂ +Â U calculations predict an optimal Fe - substrate distance of 3.5Â Ã
and a ferromagnetic exchange coupling of FeP to the substrate, in accordance with recent experiments. For Fe-porphyrin chloride (FePCl), on the other hand, an antiferromagnetic coupling is computed to be more favorable. Our study demonstrates that due to an indirect exchange interaction, which is mediated through the four nitrogen atoms, ferromagnetic ordering on the FeP is stabilized.
Keywords
Related Topics
Physical Sciences and Engineering
Chemistry
Physical and Theoretical Chemistry
Authors
P.M. Oppeneer, P.M. Panchmatia, B. Sanyal, O. Eriksson, Md.E. Ali,