Spin Correlations in the Different Phases of URu$_2$Si$_2$

ORAL

Abstract

We report a neutron scattering study of the magnetic excitation spectrum in three temperature and pressure driven phases of URu$_2$Si$_2$: the paramagnetic, `hidden order' and antiferromagnetic phases. The experiment was conducted using the novel neutron scattering spectrometer MACS at the NIST Center for Neutron Research[1]. Wide-angle detector coverage offers comprehensive scattering data covering an entire plane in momentum space with excellent energy resolution. The ambient pressure data show a magnetic excitation spectrum characteristic of Fermi surface nesting in the paramagnetic phase and the development of a gap in the excitation spectrum upon cooling through the T$_C$~=~17.5~K phase transition. The efficiency of MACS allowed a comprehensive data set in the high-pressure phase. Throughout the (H0L) scattering plane we find qualitatively similar excitations as in the hidden order phase though with a substantial reduction in the overall spectral weight and an upward shift in energy. These data should allow a critical evaluation of recent theoretical work to understand the small and large moment phases of URu$_2$Si$_2$. [1] J.A. Rodriguez-Rivera, Meas. Sci. Technol. 19, 034023 (2008).

–

Authors

  • Travis J. Williams

    • McMaster University

  • H. Barath

    • Johns Hopkins University

  • Z. Yamani

    • Canadian Neutron Beam Centre, NRC Chalk River

  • J.A. Rodriguez-Rivera

    • NIST Center for Neutron Research

  • J.B. Leao

    • NIST Center for Neutron Research

  • J.D. Garrett

    • McMaster University

  • G.M. Luke

    • McMaster University

  • W.J.L. Buyers

    • Canadian Neutron Beam Centre, NRC Chalk River

  • C. Broholm

    • NIST Center for Neutron Research