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We report an inelastic neutron scattering study of candidate multiferroic ErFeO 3 , a compound that has been previously reported to have three different magnetic states and undergoes signatures of Fe 3 + − Er 3 + cooperative coupling. The spectrum at low energy transfer is dominated by excitations of the Er 3 + character, even above the Er 3 + antiferromagnetic ordering temperature of 4.5 K. In addition, a crystalline electric field excitation at 6 meV exhibits additional energy splitting upon cooling through 4.5 K with mode-dependent polarization. This indicates different moment directions for these modes, an interesting consequence of C y ordering of the Er 3 + moments. [ABSTRACT FROM AUTHOR]

Kondo insulator FeSb2 with large Seebeck coefficient would have potential in thermoelectric applications in cryogenic temperature range if it had not been for large thermal conductivity κ. Here we studied the influence of different chemical substitutions at Fe and Sb site on thermal conductivity and thermoelectric effect in high quality single crystals. At 5% of Te doping at Sb site, thermal conductivity is suppressed from ∼250 W/Km in undoped sample to about 8 W/Km. However, Cr and Co doping at Fe site suppresses thermal conductivity more slowly than Te doping, and even at 20% Cr/Co doping the thermal conductivity remains ∼30 W/Km. The analysis of different contributions to phonon scattering indicates that the giant suppression of κ with Te is due to the enhanced point defect scattering originating from the strain field fluctuations. In contrast, Te-doping has small influence on the correlation effects and then for small Te substitution the large magnitude of the Seebeck coefficient is still preserved, leading to the enhanced thermoelectric figure of merit (ZT ∼0.05 at ∼100 K) in Fe(Sb0.9Te0.1)2. [ABSTRACT FROM AUTHOR]

The electric field dependence on the dielectric properties of the porous ceramics was studied theoretically. The dielectric constant of the porous ceramics under certain direct current (dc) bias field and the real strength electric field in the porous ceramics were given quantitatively. As the pore can share the electric field, the tunability of the porous ceramics will be decreased when the porosity increases. The dielectric constant evolution of Ba0.6Sr0.4TiO3-based porous ceramics with the dc bias electric field can be successfully explained by our theoretical results. Taking Ba0.6Sr0.4TiO3-based porous ceramic samples, for example, there is good correspondence between the theoretical and the experimental results. [ABSTRACT FROM AUTHOR]