Magnetic Coulomb Phase in the Spin Ice Ho2Ti2O7.
Fennell, T. 1,*; Deen, P. P. 1; Wildes, A. R. 1; Schmalzl, K. 2; Prabhakaran, D. 3; Boothroyd, A. T. 3; Aldus, R. J. 4; McMorrow, D. F. 4; Bramwell, S. T. 4
[Report] Science. 326(5951):415-417, October 16, 2009.

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: Spin-ice materials are magnetic substances in which the spin directions map onto hydrogen positions in water ice. Their low-temperature magnetic state has been predicted to be a phase that obeys a Gauss' law and supports magnetic monopole excitations: in short, a Coulomb phase. We used polarized neutron scattering to show that the spin-ice material Ho2Ti2O7 exhibits an almost perfect Coulomb phase. Our result proves the existence of such phases in magnetic materials and strongly supports the magnetic monopole theory of spin ice.

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