Regensburg 2010 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 5: CE: Low-dimensional Systems - Materials 1
TT 5.11: Talk
Monday, March 22, 2010, 17:00–17:15, H18
Analyzing the complex spin-coupling structure in the single-molecule magnet Mn12wheel by inelastic neutron scattering — •Joscha Nehrkorn1, Oliver Waldmann1, Taketo Tagushi2, George Christou2, Thierry Strässle3, Philip L. W. Tregenna-Pigott3, and Hannu Mutka4 — 1Physikalisches Institut, Universität Freiburg, 79104 Freiburg, Germany — 2Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, USA — 3LNS, ETH Zürich & Paul Scherrer Institut, 5232 Villigen PSI, Switzerland — 4Institut Laue-Langevin, 38042 Grenoble, France
Recently the single-molecule magnet (SMM) [Mn12(O2CMe)14(R-mda)8], or Mn12wheel in short, has attracted interest because of its unusual quantum tunneling transitions in the magnetization, which were explained by describing it as a dimer of two magnetically coupled SMM subunits [1,2]. In order to analyze the underlying complicated spin structure we performed inelastic neutron scattering experiments. They show that the model of two coupled SMMs has to be refused. A microscopic model was devised which reproduces the data and provides values for the exchange coupling and magnetic anisotropy parameters. By using basic principles for bipartite lattices the low-energy sector can be reduced again to that of two coupled subunits, which, however, are substantially different than the two subunits in the originally proposed dimer model. The new model resolves some controversies as regarding the magnetic tunneling transitions.
[1] C. Ramsey et al., Nature Physics 4, 277 (2008)
[2] W. Wernsdorfer et al., Phys. Rev. Lett 101, 237204 (2008)