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Abstract: The solid solution between the ferromagnetic metal and the enhanced paramagnetic metal was recently reported (Phys. Rev. B 69 (2004) 024410), and an unexpected feature was found in the specific heat data at of . The feature was reinvestigated further by characterizing additional samples with various Ru concentrations in the vicinity of . Specific heat and magnetic susceptibility data indicate that the feature reflects a peculiar magnetism of the doped perovskite, which appears only in the very narrow composition range . [Copyright &y& Elsevier]

Abstract: We performed Co nuclear quadrupole resonance (NQR) measurements on bilayered hydrate cobaltate . The sample we used demonstrates a magnetic transition at , which is observed from susceptibility, nuclear spin-lattice relaxation rate, and NQR spectrum measurements. We observed inhomogeneous broadening of the NQR spectrum below . In order to interpret the internal field distribution, we numerically solved a nuclear-spin Hamiltonian including the nuclear quadrupole interaction and the Zeeman interaction, and estimated the internal fields from the observed Co-NQR spectrum. It is considered that the internal fields possess weak modulation. The obtained internal-field distribution suggests the occurrence of the spin-density-wave ordering. [Copyright &y& Elsevier]

Abstract: The metallic compound forms a full range solid solution to the insulating phase . At a Na concentration of 0.25mole per formula unit, we found an unexpected contribution to the specific heat at low temperature [K. Yamaura, et al., Chem. Mater. 17 (2005) 359]. To address this issue, specific heat and AC and DC magnetic susceptibilities were additionally measured under a variety of conditions for the sample. A new set of data clearly indicate the additional specific heat is magnetic in origin; however, the magnetic entropy is fairly small ( of Schottky term for a simple splitting doublet), and there is no other evidence to suggest that a magnetic phase transition is responsible for the anomalous specific heat. [Copyright &y& Elsevier]

Abstract: Low-temperature specific-heat data C(T) of two Na0.35CoO2. 1.3H2O samples (I and II) with temperature T down to 0.6K without and with magnetic field of 8T are presented. The normal-state linear coefficient of specific heat γ n, Debye temperature Θ D, superconducting transition temperature T c, specific heat jump at T c, ΔC/γnsT c, and superconducting volume of fraction (SVF) are 14.89mJ/molK2, 503, 4.7K, 1.96, and 26.6% for sample I and 13.94mJ/molK2, 362, 4.5K, 1.45, and 47.4% for sample II, respectively. Because the superconducting properties may depend on the water content of sample, it is found that the better quality (higher SVF) of sample, the nodal order parameter is better than BCS isotropic s-wave model in describing the gap function of this interesting compound Na0.35CoO2. 1.3H2O. [Copyright &y& Elsevier]

Abstract: We measured -NMR spectra and nuclear spin-lattice relaxation rates ) of superconducting and non-superconducting bilayer hydrates , ). The central resonance frequencies show small but various shifts due to differences in the shielding effect by intercalated molecules. The different shielding effect also gives a large difference in the magnitude of . [Copyright &y& Elsevier]

Abstract: We have performed Co nuclear quadrupole resonance (NQR) measurements in various bilayered-hydrate (BLH) compounds, showing superconducting (SC) and non-SC characteristics. A weak magnetic order was found in a BLH sample with a longer -axis lattice parameter. We also found that the NQR frequency arising from the transition is related to the ground state of this system. A phase diagram is developed, in which the superconducting and magnetic-order temperature and are plotted with respect to . [Copyright &y& Elsevier]

Abstract: The field-swept nuclear magnetic resonance (NMR) spectra of 59Co in the superconductor have been measured at several magnetic fields below . The anisotropic Knight shift seems to decrease with decreasing temperature without broadening of the spectrum, indicating either the site-selective diamagnetic effect, which may result in the spin-triplet superconductivity, or the decrease of the intrinsic spin shift. Analysis of the magnetic field dependence of the Knight shift at 2K revealed that the superconductivity occurs in an unconventional way. [Copyright &y& Elsevier]