Diffuse Scattering Spectrometer
D7 has been dismantled. The new permanently-polarized diffuse scattering spectrometer D007 will deliver its first neutrons in 2024.
Pinch Points in Spin Ice
Spin ice materials are magnetic analogues of water ice, where the ice rules arise from spin rather than positional degrees of freedom. Theoretically, the spin ice ground state is predicted to have hyperbolic long ranged correlations and magnetic monopole excitations. The signatures of these in neutron scattering are pinch-points, bow-tie like diffuse features centered on nuclear Bragg positions. Polarized neutron scattering data taken on a single crystal of Ho2Ti2O7 using D7 are shown in the figure. In unpolarized data (C), the pinch points are not visible, whereas in the polarized spin flip data (A), they are immediately apparent. The data are furthermore well modeled by Monte Carlo simulations (D-F).
Ref: T. Fennell, P. P. Deen, A. R. Wildes, K. Schmalzl, D. Prabhakaran, A. T. Boothroyd, R. J. Aldus, D. F. McMorrow, and S. T. Bramwell, Science 326, 5951 (2009)