The physical properties of borocarbide superconductor Y1−xSmxNi2B2C (x≦0.25) and Y1−xSmxPd5B3C0.4 (x≦0.4)

We have investigated the magnetic and transport properties of borocarbide superconductors YNi2B2C and YPd5B3C0.4 with Yttrium partially substituted by Samarium. The upper critical fields HC2 are determined by the scaling analysis of the thermal fluctuation magnetoconductivity. Around the transition region, the thermal fluctuation magnetoconductivity can be scaled by a universal function for all applied magnetic fields. The formula HC2(T)=HC2(0)[1−(T/TC)3/2]3/2 of a narrow-band pairing mechanism gives an excellent fit to the value of upper critical field HC2(0)=7.6 T in the Y0.8Sm0.2Pd5B3C0.4 compound. The superconducting coherence length ξ is determined to be 6.58 nm, the Ginzburg–Landau parameter κ is 29 and the penetration depth λ is 191 nm.