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College Park, Maryland      June 6 - 10 , 2004

W2-D2 (2:00 PM): Spin-waves in antiferromagnetic Kagome lattice

K. Matan (Department of Physics, MIT), D. Grohol, D. Nocera (Department of Chemistry, MIT), S. -H. Lee (National Institute of Standards and Technology), S. Nagler (HFIR Center for Neutron Scattering, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.), Y. S. Lee (Department of Physics, MIT)

We have used inelastic neutron scattering to study spin-waves in single crystal samples of the antiferromagnetic kagome lattice compound, KFe3(OH)6(SO4)2. The 5/2 Fe3+ spins on the kagome lattice order three dimensionally for temperatures below the Neel temperature, TN = 65 K. Spin-waves were measured at T = 10 K, much lower than TN. We have observed a novel weakly dispersive “zero-energy mode”, which is a consequence of the geometrical frustration. A spin Hamiltonian, which includes nearest-neighbor, second-nearest-neighbor interactions, easy-plane and easy-axis anisotropies, provides a good fit to our spin-wave data. We will discuss the implications of our results for the physics of the ideal kagome lattice.

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