45 research outputs found

    Anomalous thermal expansion and strong damping of the thermal conductivity of NdMnO3_3 and TbMnO3_3 due to 4f crystal-field excitations

    Full text link
    We present measurements of the thermal conductivity κ\kappa and the thermal expansion α\alpha of NdMnO3_3 and TbMnO3_3. In both compounds a splitting of the 4f4f multiplet of the R3+R^{3+} ion causes Schottky contributions to α\alpha. In TbMnO3_3 this contribution arises from a crystal-field splitting, while in NdMnO3_3 it is due to the Nd-Mn exchange coupling. Another consequence of this coupling is a strongly enhanced canting of the Mn moments. The thermal conductivity is greatly suppressed in both compounds. The main scattering process at low temperatures is resonant scattering of phonons between different energy levels of the 4f4f multiplets, whereas the complex 3d magnetism of the Mn ions is of minor importance.Comment: 9 pages including 6 figure

    General formula for determination of cross-section from measured SANS intensities

    Full text link

    A novel heavy-fermion state in CaCu_3Ru_4O12

    Full text link
    We have measured susceptibility, specific heat, resistivity, and thermopower of CaCu3_3Ti4−x_{4-x}Rux_xO12_{12} and CaCu3−y_{3-y}Mny_yRu4_4O12_{12}, and have found that CaCu3_3Ru4_4O12_{12} can be regarded as a heavy-fermion oxide in d-electron systems. The Kondo temperature is near 200 K, and the susceptibility (1.4×10−3\times10^{-3} emu/Cu mol) and the electron specific heat coefficient (28 mJ/Cu molK2^2) are moderately enhanced. The resistivity is proportional to T2T^2 at low temperatures, and satisfies the Kadowaki-Woods relation. The heavy-fermion state comes from the interaction between the localized moment of Cu 3d and the conduction electron of Ru 4d. An insulator-metal transition occurs between x=1.5x=1.5 and 4 in CaCu3_3Ti4−x_{4-x}Rux_xO12_{12}, which can be regarded as a transition from magnetic insulator to heavy-fermion metal.Comment: 4 pages, 5 figures, submitted to J. Phys. Soc. Jp
    corecore