1,732 research outputs found

    Single crystal growth and physical properties of a new uranium compound URhIn5_5

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    We have grown the new uranium compound URhIn5_5 with the tetragonal HoCoGa5_5-type by the In self flux method. In contrast to the nonmagnetic ground state of the isoelectronic analogue URhGa5_5, URhIn5_5 is an antiferromagnet with antiferromagnetic transition temperature TNT_{\rm N} = 98 K. The moderately large electronic specific heat coefficient γ\gamma = 50 mJ/K2^2mol demonstrates the contribution of 5ff electrons to the conduction band. On the other hand, magnetic susceptibility in the paramagnetic state roughly follows a Curie-Weiss law with a paramagnetic effective moment corresponding to a localized uranium ion. The crossover from localized to itinerant character at low temperature may occur around the characteristic temperature 150 K where the magnetic susceptibility and electrical resistivity show a marked anomaly.Comment: 7 pages, 7 figure

    Evidence for ferromagnetic spin-pairing superconductivity in UGe2_2: A 73^{73}Ge-NQR study under pressure

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    We report that a novel type of superconducting order parameter has been realized in the ferromagnetic states in UGe2_2 via 73^{73}Ge nuclear-quadrupole-resonance (NQR) experiments performed under pressure (PP). Measurements of the nuclear spin-lattice relaxation rate (1/T1)(1/T_1) have revealed an unconventional nature of superconductivity such that the up-spin band is gapped with line nodes, but the down-spin band remains gapless at the Fermi level. This result is consistent with that of a ferromagnetic spin-pairing model in which Cooper pairs are formed among ferromagnetically polarized electrons. The present experiment has shed new light on a possible origin of ferromagnetic superconductivity, which is mediated by ferromagnetic spin-density fluctuations relevant to the first-order transition inside the ferromagnetic states.Comment: 5 pages, 5 figure

    Dynamical structure factors of S=1/2S=1/2 two-leg spin ladder systems

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    We investigate dynamical properties of S=1/2S=1/2 two-leg spin ladder systems. In a strong coupling region, an isolated mode appears in the lowest excited states, while in a weak coupling region, an isolated mode is reduced and the lowest excited states become a lower bound of the excitation continuum. We find in the system with equal intrachain and interchain couplings that due to a cyclic four-spin interaction, the distribution of the weights for the dynamical structure factor and characteristics of the lowest excited states are strongly influenced. The dynamical properties of two systems proposed for SrCu2O3{\rm SrCu_2O_3} are also discussed.Comment: 5 pages, 6 figure

    Unusual behaviours and Impurity Effects in the Noncentrosymmetric Superconductor CePt3Si

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    We report a study in which the effect of defects/impurities, growth process, off-stoichiometry, and presence of impurity phases on the superconducting properties of noncentrosymmetric CePt3Si is analysed by means of the temperature dependence of the magnetic penetration depth. We found that the linear low-temperature response of the penetration depth -indicative of line nodes in this material- is robust regarding sample quality, in contrast to what is observed in unconventional centrosymmetric superconductors with line nodes. We discuss evidence that the broadness of the superconducting transition may be intrinsic, though not implying the existence of a second superconducting transition. The superconducting transition temperature systematically occurs around 0.75 K in our measurements, in agreement with resistivity and ac magnetic susceptibility data but in conflict with specific heat, thermal conductivity and NMR data in which Tc is about 0.5 K. Random defects do not change the linear low-temperature dependence of the penetration depth in the heavy-fermion CePt3Si with line nodes, as they do in unconventional centrosymmetric superconductors with line nodes.Comment: To appear in New Journal of Physic
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