Field-Induced Transition on Triangular Plane in the Spin Ice Compound Dy2Ti2O7

The origin of the lowest-temperature anomaly reported several years ago using a polycrystalline sample of the spin ice compound Dy2Ti2O7 had remained unresolved. Here we finally clarify its origin by susceptibility measurements down to 65 mK using single crystals under accurate control of the magnetic fields in two independent directions. We demonstrate that the transition is induced under a subtle field combination that precisely cancel the nearest-neighbor spin interactions acting on the spins on the triangular lattice within the pyrochlore structure. Contrary to the other two fieldinduced transitions, this transition is driven only by the interactions beyond the nearest neighbors. Our observation thus provides the first qualitative evidence for the essential importance of the dipolar interaction beyond the nearest neighbors in the spin ice.Comment: submitted to PR

Magnetodielectric Response of the Spin-Ice Dy2Ti2O7

We report the magneto-dielectric response of single crystals of the spin-ice compound Dy2Ti2O7 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 Dy3+ 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 magneto-dielectric response can be a high-sensitivity local probe of the spin state of geometrically frustrated systems.Comment: 6 pages, 6 figure

Superconductivity in In-doped AgPbBiTe3 compounds synthesized by high-pressure synthesis

NaCl-type metal tellurides (MTe) have been widely studied due to unique physical properties. We investigated the In-doping effects on structural and physical properties of Na-Cl type (AgPbBi)(1-x)/3InxTe and the superconducting properties of the In-doped samples. Polycrystalline samples with x = 0-0.5 were synthesized by utilizing high-pressure synthesis. For x = 0.2-0.5, superconductivity was observed in magnetization measurements, where the highest transition temperature (Tc) was 2.8 K for x = 0.4. We measured specific heat for x = 0.4 and confirmed the bulk nature of the superconductivity. The evolution of the Seebeck coefficient and lattice constant by In doping suggests that In valence state is In+3, and the In doping generates electron carriers in the (AgPbBi)(1-x)/3InxTe system.Comment: 12 pages, 5 figure

93Nb- and 27Al-NMR/NQR studies of the praseodymium based PrNb2Al20

International Conference on Strongly Correlated Electron Systems 2014 (SCES2014