Precise Chemical, Electronic, and Magnetic Structure of Binuclear Complexes Studied by Means of X-ray Spectroscopies and Theoretical Methods

We investigate two planar complexes MnNi and CoNi (see Scheme 1) by X-ray photoelectron spectroscopy (XPS) and ultralow-temperature X-ray magnetic circular dichroism (XMCD). In this way the valence states as well as the presence of uncompensated magnetic moments are obtained. The magnetism has been...

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Veröffentlicht in:Journal of physical chemistry. C 2011-12, Vol.115 (50), p.25030-25039
Hauptverfasser: Kuepper, Karsten, Benoit, David M, Wiedwald, Ulf, Mögele, Florian, Meyering, Andreas, Neumann, Manfred, Kappler, Jean-Paul, Joly, Loïc, Weidle, Stefan, Rieger, Bernhard, Ziemann, Paul
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Sprache:eng
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Zusammenfassung:We investigate two planar complexes MnNi and CoNi (see Scheme 1) by X-ray photoelectron spectroscopy (XPS) and ultralow-temperature X-ray magnetic circular dichroism (XMCD). In this way the valence states as well as the presence of uncompensated magnetic moments are obtained. The magnetism has been probed at a temperature of 0.6 K in order to reveal the magnetic ground state properties. We find that divalent Ni ions are in a diamagnetic low spin ground state in both complexes; however, in MnNi a small fraction of divalent nickel high-spin ions leads to a residual XMCD signal, indicating parallel spin alignment with the Mn spins. Mn and Co are found to be in a divalent high-spin configuration in both compounds. Theoretically, we address the energetic ordering of the different possible spin states of the binuclear complexes using (zeroth-order) relativistic approximation density functional calculations and a triple-ζ quality basis set. These results show that intermediate-spin states are often favored over low-spin states for most both metal combinations, in qualitative agreement with our experimental observations.
ISSN:1932-7447
1932-7455
DOI:10.1021/jp2069804