We investigated low-temperature specific heat of the filled skutterudite compound LaOs₄As₁₂ with a transition temperature T_{c} = 3.2 K. A moderate size of a specific-heat jump points at a weak electron-phonon coupling in this material. At T < T_{c}, the electronic contribution to the specific heat was found to be at variance with the predictions for an s-wave superconductor with one energy gap. Additionally, we observed an upward curvature of the upper critical field near the transition temperature. Both features provide some indications towards multiband superconductivity, although anisotropy effects as a viable cause of the observed anomalies in LaOs₄As₁₂ cannot be excluded. Similarities to a probable two-band superconductor LaRu₄As₁₂ are discussed.
The compound ThIr₂Si₂ crystallizes with a tetragonal crystal structure of the CaBe₂Ge₂-type (space group P4/nmm). Its low-temperature physical properties were investigated by means of magnetization, electrical resistivity, and heat capacity measurements, performed down to 0.35 K. The experiments revealed bulk superconductivity below T_{c} = 2 K. The obtained data indicate that ThIr₂Si₂ is a weakly-coupled type-II BCS superconductor.
We investigated the magnetic properties of chalcogenide-spinel superconductor CuRh₂S₄ under pressure and estimated the pressure dependence of the superconducting parameters. With increasing pressure, the superconducting transition temperature (T_{c}), thermodynamic critical field (H_{c}), upper critical field (H_{c2}), penetration depth (λ), and GL parameter (κ) increase. Meanwhile, the lower critical field (H_{c1}) is unchanged and the Ginzburg-Landau coherence length (ξ_{GL}) is reduced by pressurization. The increasing value of κ indicates enhanced characteristics of the type-II superconductor CuRh₂S₄.
We report researches for superconductivity and the effect of negative magnetisation in the RFe_4Al_8 (R = Lu, Yb) compounds by means of magnetic measurements and microwave absorption. Contrary to the earlier reports we do not confirm the existence of any traces of superconductivity in these compounds. Instead of the superconductivity and the Meissner effect, the YbFe_4Al_8 compound exhibits the effect of negative magnetisation, whereas the LuFe_4Al_8 compound shows an exact antiferromagnetic behaviour.
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