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College Park, Maryland      June 6 - 10 , 2004

TP66: Quasielastic scattering in the magnetic spinel Co2RuO4

G. E. Granroth, D. Abernathy (Spallation Neutron Source, Oak Ridge National Laboratory; Condensed Matter Sciences Division, Oak Ridge National Laboratory), S. E. Nagler (Condensed Matter Sciences Division, Oak Ridge National Laboratory), D. Mandrus (Condensed Matter Sciences Division, Oak Ridge National Laboratory; Department of Physics and Astronomy, University of Tennessee), V. Keppens (Department of Physics, University of Mississippi, Oxford, MS 38677), J. R. D. Copley (NIST Center for Neutron Research)

Bulk magnetization measurements of the spinel Co2RuO4 have revealed a “spin glass like” ground state [1]. To further elucidate the properties of this ground state, temperature (T) dependent quasielastic neutron scattering studies have been performed using the DCS instrument at NIST. For T greater than the spin glass transition temperature (Tg ~ 15 K), the quasielastic peak can be fit by a Lorentzian of width 181 ± 9 μeV convoluted with the instrumental resolution. Furthermore the Q dependence of the scattering is broad and oscillatory consistent with short range ordered states involving nearest and next nearest neighbor sites [2]. For T < Tg , approximately 1/3 of this scattering is moved to the elastic position at a Q corresponding to the (200) position of the spinel lattice. The other 2/3 of the scattering remains in a Lorentzian component of width 130 ± 10 μeV. This behavior is consistent with a reduction of short time scale dynamics observed in a spin glass.

[1] D. Mandrus, V. Keppens, and B. C. Chakoumakos, Mat. Res. Bull., 34, 1013 (1999).
[2] G. E. Granroth et al. to be published.

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