J. Phys. Soc. Jpn. 78, 103706 (2009) [4 Pages]
LETTERS

Observation of Magnetic Monopoles in Spin Ice

+ Affiliations
1Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-03972Department of Materials Science and Engineering, Kyoto University, Kyoto 606-85013NSL, Institute for Solid State Physics, University of Tokyo, Tokai, Ibaraki 319-11064NCNR, National Institute of Standards and Technology, Gaithersburg, MD 20899-6102, U.S.A.5Department of Electronics, Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-85506Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581

Excitations from a strongly frustrated system, the kagomé ice state of the spin ice Dy 2 Ti 2 O 7 under magnetic fields along a [111] direction, have been studied. They are theoretically proposed to be regarded as magnetic monopoles. Neutron scattering measurements of spin correlations show that close to the critical point the monopoles are fluctuating between high- and low-density states, supporting that the magnetic Coulomb force acts between them. Specific heat measurements show that monopole-pair creation obeys an Arrhenius law, indicating that the density of monopoles can be controlled by temperature and magnetic field.

©2009 The Physical Society of Japan

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