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The electronic structure and spin polarization of bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II)

David Scott Wisbey, University of Nebraska - Lincoln

Abstract

The electronic structure of bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (or Cu(CNdpm)2), (C24H36N2O 4Cu, Cu(II)) is spin polarized. Spin polarization was observed in molecular thin films of the metal organic molecule bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (or Cu(CNdpm)2), (C24H36N2O 4Cu, Cu(II)) deposited on Co(111) using spin polarized photoemission. The spin polarization of Cu(CNdpm)2 deposited on Co(111) is coverage dependent, but deviates from the mean field (Ginzburg-Landau) model for a simple paramagnet on a ferromagnet. The results are, nonetheless, seen to be consistent with magnetometry and the predicted density of states. Weak ferromagnetic interaction is implicated between molecules by a positive Weiss constant. A nonzero coercivity is observed when an external magnetic field is applied. For Cu(CNdpm)2 deposited on Co(111), the induced spin polarization asymmetry was found to favor select molecular orbitals consistent with calculations. The results indicate a strong influence of the ferromagnetic Co(111) substrate and some extramolecular coupling. ^ The metal-organic molecule bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (Cu(CNdpm)2), (C24H36N2O 4Cu, Cu(II)), is a copper spin ½ system with a magnetic moment of 1.05±0.04 μB per molecule, slightly smaller than the 1.215+0.02 μB per molecule for the larger size copper spin ½ system C36H 48N4O4Cu * C4H8O (bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) 4,4'-bipyridylethene * THF). There is generally good agreement between photoemission from vapor deposited thin films of the C24H36N 2O4Cu on Cu(111) and Co(111) and model calculations. Although this molecule is expected to have a gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, the molecule remains surprisingly well screened in the photoemission final state. ^ Using light polarization dependent angle-resolved photoemission, the metal-organic molecule bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (or Cu(CNdpm)2), (C24H36N2O 4Cu, Cu(II)) is observed to adopt a preferential orientation that depends on film thickness and substrate when deposited on Co(111) and Cu(111). In addition, the final state binding energies change with film thickness, suggesting that the substrates affect the screening or charging in the photoemission final state.^

Subject Area

Chemistry, Organic|Physics, General|Physics, Condensed Matter

Recommended Citation

Wisbey, David Scott, "The electronic structure and spin polarization of bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II)" (2008). ETD collection for University of Nebraska - Lincoln. AAI3338833.
http://digitalcommons.unl.edu/dissertations/AAI3338833

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