Ru-NMR Studies and Specific Heat Measurements of Bi_3Ru_3O_<11> and La_4Ru_6O_<19> (Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties)

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Specific heats measurements and Ru-NMR studies have been carried out for Bi_3Ru_3O_<11> and La_4Ru_6O_<19>, which commonly have three-dimensional linkages of edge-sharing pairs of RuO_6 octahedra. The Knight shifts, the nuclear spin-lattice relaxation rates 1/T_1 and the electronic specific heats C_<el> of these systems exhibit anomalous temperature (T) dependence at low temperatures, as was pointed out by Khalifah et al. [Nature 411 (2001) 660.] for the latter system based on their experimental data of the resistivity, magnetic susceptibility and electronic specific heat. Ratios of 1/T_1T to the square of the spin component of the isotropic Knight shift, K_<spin> estimated for these systems at low temperatures suggest that they have antiferromagnetic (AF) spin fluctuations. It is confirmed by the fact that the T-dependences of 1/T_1T and C_<el>/T of the present systems can be explained by the self-consistent renormalization theory for three dimensional itinerant electron systems with AF spin fluctuations. All these results suggest that the AF fluctuations are the primary origin of the characteristics of their low temperature physical behavior.
社団法人日本物理学会の論文
2004-03-15