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MA: Magnetismus

MA 37: Molecular Magnetism

MA 37.8: Talk

Friday, March 31, 2006, 12:30–12:45, HSZ 403

Tuning the magnetic ground state of a novel tetranuclear Nickel(II) molecular complex by high magnetic fields — •C. Golze^1,2, A. Alfonsov¹, R. Klingeler^1,3, B. Büchner¹, V. Kataev¹, C. Mennerich², H.-H. Klauss², M. Goiran³, J.M. Broto³, H. Rakoto³, S. Demeshko⁴, G. Leibeling⁴, and F. Meyer⁴ — ¹IFW Dresden, Germany — ²TU Braunschweig, Germany — ³LNCMP Toulouse, France — ⁴University Göttingen, Germany

Electron spin resonance and magnetization data in magnetic fields up to 50 T of a novel multicenter magnetic molecular complex [(L)2Ni₄(N₃)(O₂C Ada)₄](Cl O₄) are reported. In this compound, four Ni spins each S = 1 are coupled in a single molecule via the central µ₄-azide bridge which provides paths for magnetic exchange. A complex ESR spectrum comprising four resonance modes has been observed. Analysis of the frequency and temperature dependence of the ESR signals yields the relevant parameters of the spin Hamiltonian, in particular the single ion anisotropy gap and the g factor, which enables the calculation of the complex energy spectrum of the spin states in a magnetic field. The experimental results give compelling evidence for tuning the ground state of the molecule by magnetic field from a nonmagnetic state at small fields to a magnetic one in strong fields owing to the spin level crossing at a field of ≈ 25 T.