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College Park, Maryland      June 6 - 10 , 2004

TP50: Inelastic Neutron Scattering Studies of the Single Molecule Magnet {Fe30Mo72}

V. O. Garlea (Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011), S. E. Nagler (Oak Ridge National Laboratory), J. L. Zarestky, C. Stassis, D. Vaknin, P. K÷gerler (Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011), D. F. McMorrow (Ris° National Laboratory, DK-4000, Roskilde, Denmark; Department of Physics & Astronomy University College London, UK), C. Niedermayer (Laboratory for Neutron Scattering, Paul Scherrer Institute & ETH Zurich, CH-5232 Villigen, Switzerland), Y. Qiu (NIST Center for Neutron Research , Gaithersburg, Maryland, 20899 & Department of Materials Science and Engineering, University of Maryland, College Park, Maryland, 20742)

Materials consisting of magnetic molecules are ideal prototypes for the study of fundamental problems of magnetism at the nanoscale level. The Keplerate material {Fe30Mo72} is a singlet ground state single molecule magnet system with isolated clusters of 30 s=5/2 ions on the vertices of an isododecahedron. We report cold-neutron inelastic scattering measurements on {Fe30Mo72} carried out using the triple axis spectrometer RITA-II at PSI and the Disc Chopper Spectrometer at NIST Center for Neutron Research. Results for temperatures T < 200 mK reveal a magnetic excitation at an energy transfer near 0.65 meV. The peak broadens and shifts dramatically in the presence of an applied magnetic field. The results are discussed in the context of the effective rotational band model of Luban and co-workers [1].

[1] J. Schnack, M. Luban, and R. Modler, Europhys. Lett. 56, 863 (2001).

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