Dresden 2003 – scientific programme

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MA: Magnetismus

MA 26: Elektronentheorie

MA 26.6: Talk

Thursday, March 27, 2003, 16:30–16:45, HSZ/401

Lineshape and Relaxation Studies on Mn₁₂ac — •Suriyakan Vongtragool¹, Boris Gorshunov¹, Martin Dressel¹, and Alexandra Mukhin² — ¹1.Physikalisches Institut, Universität stuttgart, Germany — ²General Physics Institute, Russian Academy of Sciences, Moscow, Russia

The molecular magnet Mn₁₂ac has a high spin S=10 ground state. Direct observations of the crystal field transitions by using a frequency-domain magnetic spectroscopy provide the corresponding zero field splitting parameters. Investigation of magnetodipole transitions lineshape (Gaussian) and linewidth in single crystals gives information on the cluster environment and internal fields. Depending on history, symmetric zero-field cooled (zfc) or asymmetric (fc) lineshapes are obtained due to inhomogeneous broadening with Δ D=0.01D.We also present the detailed studies of quantum tunneling and relaxation phenomena which are directly observed by our technique, which can probe local populations of separate spin states. The spin relaxation of Mn₁₂ac is studied by reversing the external magnetic field. Below T≈ 2 K resonant quantum tunneling is directly observed as a tunnel dip in the absorption spectra of polycrystals.