| Summary: | The intrinsic noncollinear spin patterns in rare-earth pyrochlore are physically interesting, due to their many emergent properties (e.g., spin-ice and monopole-type excitation). Recent works have suggested that the magnetic monopole excitation of spin-ice systems is magnetoelectric active, but this fact has rarely been confirmed via experiment. In this work, we performed a systematic experimental investigation on the magnetoelectricity of Dy _2 Ti _2 O _7 by probing the ferroelectricity, spin dynamics, and dielectric behaviors. Two ferroelectric transitions at T _c _1 = 25 K and T _c _2 = 13 K were observed. Remarkable magnetoelectric coupling was identified below the lower transition temperature, with significant suppression of the electric polarization on applied magnetic field. Our results show that the lower ferroelectric transition temperature coincides with the Ising-spin paramagnetic transition point, below which the quasi-particle-like monopoles are populated, which indicates implicit correlation between electric dipoles and spin moments. The possible magnetoelectric mechanisms are discussed. Our results can be used for more investigations to explore multiferroicity in these spin-ice systems and other frustrated magnets.
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