Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 14: Spin Systems and Itinerant Magnets
TT 14.1: Vortrag
Dienstag, 27. März 2007, 14:00–14:15, H19
Static and Dynamic Properties of an [Fe13] Cluster — •Joris van Slageren1, Patrick Rosa2, and Andrea Caneschi3 — 11. Physikalisches Institut, Universität Stuttgart — 2ICMCB, CNRS, Pessac, France — 3INSTM, UdR Firenze, University of Florence, Italy
The static and dynamic magnetic properties of an [Fe13] cluster were investigated using several experimental techniques. The cluster crystallizes in a cubic space group, but careful investigation of the crystallographic data revealed that the symmetry is distorted locally. DC magnetic susceptibility measurements showed the presence of competing antiferromagnetic isotropic exchange interactions leading to a high-spin ground state and many low-lying excited spin states, which was confirmed by inelastic neutron scattering measurements. From high-field electron paramagnetic resonance measurements a small zero-field splitting of the spin ground state was inferred, which supports the local symmetry distortion found in the crystallographic studies. The spin dynamics slows down at sub-kelvin temperatures, where ac susceptibility measurements indicated that part of the sample shows superparamagnetic-like behavior and the other part relaxes through magnetization tunneling. The Mössbauer data confirmed the slowing down of the spin dynamics, indicating that this occurs mainly in the peripheral spins.