We report the magnetodielectric response of single crystals of the spin-ice compound ${\mathrm{Dy}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ down to 0.26 K. The dielectric constant under zero magnetic field exhibits a clear decrease reflecting the development of the local two-spins-in, two-spins-out structure below about 1.2 K. Both the real and imaginary parts of the dielectric constant under magnetic fields sensitively respond to various changes in the spin structures. We found that the real part can be described in terms of local spin correlations among the moments of tetrahedra, rather than among individual ${\mathrm{Dy}}^{3+}$ moments. Using the peaks in the imaginary part, we have constructed a precise field-temperature phase diagram in the [111] field direction. We thus demonstrate that the magnetodielectric response can be a high-sensitivity local probe of the spin state of geometrically frustrated systems.

• Received 10 January 2005

DOI:https://doi.org/10.1103/PhysRevB.72.144422