Double pyrochlore Dy2Ru2O7 is synthesized and its magnetism and ferroelectricity below the Ru4+ spin ordering temperature (～100 K) are investigated. The ferroelectric transition appears at ～18 K, much higher than the Dy3+ spin ordering point at ～1.8 K and lower than the Ru4+ spin ordering point at ～100 K. The measured electric polarization at ～2 K is as big as 145 μC/m2 in the polycrystalline samples. It is argued that the ferroelectricity is possibly ascribed to the electric dipole ordering arising from the collective monopole excitations in the Dy3+ tetrahedrons in prior to the Dy3+ spin ordering into spin-ice like state below ～1.8 K.
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