Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 40: Poster II: Bio- and Molecular Magnetism (1-9); Magnetic Coupling Phenomena/Exchange Bias (10-15); Magnetic Particlicles and Clusters (16-29); Micro and Nanostructured Magnetic Materials (30-51); Multiferroics (52-64); Spin Injection in Heterostructures (65-67); Spin-Dyn./Spin-Torque (68-93); Spindependent Transport (94-108)
MA 40.9: Poster
Freitag, 27. März 2009, 11:00–14:00, P1A
Spin states of a novel Ni(II) trimer complex — •Y. Krupskaya1, A. Parameswaran1, A. Alfonsov1, R. Klingeler1, V. Kataev1, B. Büchner1, M. Gressenbuch2, and B. Kersting2 — 1IFW Dresden, D-01171 Dresden — 2Institute of Inorganic Chemistry, University of Leipzig, D-04103 Leipzig
We have investigated magnetic properties of a novel macrocyclic chelate trinuclear Ni(II)-Complex [Ni3(L)(OAc)2] with [O3N2Ni(µ-S)Ni(N2O2)(µ-S)NiN2O3] as the core by measurements of the static magnetization M and high-frequency ν tunable electron spin resonance (HF-ESR). Both temperature T and magnetic field B dependences of M reveal an appreciable antiferromagnetic coupling between three Ni(II) (3d8, SNi = 1) ions in the complex which is maintained by µ-sulphur bridges. The data on the saturation magnetization at T=2 K give evidence that the ground state of the molecule can be characterized by a total spin S0tot = 1. A strong nonlinear development of the inverse magnetic susceptibility χ(T)−1 = [M(T)/B]−1 in the range T = 2 − 100 K measured at B = 1 and 5 T indicates a thermal activation of high energy spin multiplets S1tot = 2 and S2tot = 3. In this T-regime HF-ESR measured at ν = 92 − 350 GHz and B up to 15 T reveals multiple excitations associated with the intramultiplet spin-flip transitions. The ν-dependence of the resonance field of the ESR modes yields a magnetic anisotropy gap of the order of 50 GHz (∼ 2.4 K) and a g-factor of ∼ 2.2. We propose a scheme of the energy spectrum of the spin states and discuss the relationship between magnetic interactions and the topology and chemical bonding in this spin trimer complex.