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Joachim Hewer: X-ray magnetic circular dichroism spectroscopy of single molecule magnets, 3d-4f mixed bimetallic complexes and spin frustrated complexes in isolation

Wanneer:ma 17-10-2016 11:00 - 12:00

Single Molecule Magnets (SMM) reveal exceptionally interesting magnetic properties as their magnetic moments do not emerge from macroscopic bulk ordering but from the individual inherent properties of the molecule. The molecular origin of the observed magnetic behaviour finds support from extensive studies on the these systems within crystalline material or on molecules attached to a variety of surfaces. Still in none of these experiments the molecules were fully isolated. In the bulk or at surfaces there are always interactions present which can have an effect onto their magnetic properties. Here we report the magnetic signature of a truly isolated cationic species: of the archetypal [Mn12O12(CH3COO)15(CH3CN)]+ SMM, and intrinsic spin and orbital magnetic moments of 3d-4f mixed metallic complexes of the [Fe4Ln2] (Ln = Gd, Tb) and [Mn2Ln] (Ln = Nd, Eu, Gd, Dy, Lu) type by X-ray magnetic circular dichroism (XMCD) spectroscopy and sum rule analysis.

Magnetic interactions are called frustrated, if an assembly of spins located on an assembly of atoms cannot arrange its orientation such that they profit from the magnetic interaction with its neighbors. We aim to investigate triangular antiferromagnetic oxo-centered transition metal carboxylate complexes of the structural type [M3 IIIO(CH3CO2)6L0‑3] (M = Fe, Co) which serve as model systems for the study of such a spin frustration.