Coexistence of Superconductivity and Ferromagnetic Spin-Fluctuation in Ca3Ir4Sn13 Single Crystal

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Temperature dependences of the electrical resistivity, magnetic susceptibility and specific heat have been measured on the single crystal Ca3Ir4Sn13. This compound shows a bulk superconducting transition at ${\approx}7.0$ K. We observe peak-like anomalies, which are attributed to the ferromagnetic spin-fluctuations, in susceptibility and resistivity. The resistivity shows a non Fermi-liquid behavior as $\rho=\rho_{0}+A^{*}T^{n}$ ($n=1.2$ for $H=0$) in normal state at low temperatures, and develops into a Fermi-liquid behavior by the suppression of the ferromagnetic spin fluctuation on increasing magnetic fields ($n=2$ for $H=14$ T). The superconductivity disappears for magnetic field $H\geq 7$ T as well as the diminution of the ferromagnetic spin fluctuations. We find that the superconductivity coexists with the ferromagnetic spin fluctuations and seems to cooperate in this material. The large values of $\Delta C/\gamma_{n}T_{\text{c}}=2.78$, Kadowaki–Woods ratio $A/\gamma_{n}^{2}=1.14\times 10^{-5}$ μ$\Omega$$\cdot$cm (K$\cdot$mol/mJ)2 and Wilson ratio $R_{\text{w}}=\pi^{2}k_{\text{B}}^{2}\chi_{\text{p}}/3\mu_{\text{B}}^{2}\gamma\approx 1.7$, indicate the electrons are highly correlated in this system.
2010-11-15