Berlin 2008 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 2: Towards Molecular Spintronics
DS 2.1: Hauptvortrag
Montag, 25. Februar 2008, 11:45–12:15, H 2013
Tunable electron spin resonance spectroscopy of multi-center paramagnetic molecular complexes in strong magnetic fields — •Vladislav Kataev — IFW Dresden, D-01171 Dresden
Determination of the low-energy spectrum of spin states and magnetic anisotropy is an important prerequisite on the route of functionalization of magnetically active molecular complexes for molecular based spintronics. Owing to the increasing complexity of the metal ion polynuclear complexes which combine in a single molecule a large number of interacting transition metal ions, the resulting spin states have a large multiplicity and a complex structure. High magnetic field electron spin resonance (ESR) spectroscopy enbales to selectively tune different spin states into the resonance with external microwave radiation and thus to determine the relative energies of the spin levels as well as the magnitude and sign of the magnetic anisotropy. As an example, we will discuss our recent ESR and magnetization measurements of several novel molecular complexes whose magnetic cores are built of interacting paramagnetic 3d-ions , such as, e.g., [L2Ni4(N3)(O2CAda)4](ClO4) and [(L2)Ni2(µ-pydz)(N3)2](BPh4)2. Experimental data give evidence that the ground state and magnetic anisotropy depend sensitively on the details of the intramolecular bonding geometry and ligand coordination that can be tuned by means of synthetic chemistry. Different spin states can be realized: (i) a nonmagnetic state which can be turned into a magnetic one in strong magnetic fields; (ii) a strongly magnetic ground state with substantial negative magnetic anisotropy, i.e. functionalities constitutive for applications in molecular based spintronics.