Superconductivity and magnetism in the La_2-xNd_xRh₃Si₅ system

Abstract

It is now well known that the compounds that belong to the R₂Fe₂Si₅ series exhibit unusual superconducting and magnetic properties. Although a reasonable number of studies have been made on this series, similar efforts on another series, namely, R₂Rh₃Si₅, whose structure is closely related to R₂Fe₃Si₅ have not been made. In this paper, we have established the bulk superconductivity in La₂Rh₃Si₅ below 4.4 K and bulk antiferromagnetism in Nd₂Rh₃Si₅ below 2.7 K, from resistivity, susceptibility, and heat-capacity studies. The superconducting transition temperature of (T_c) La₂Rh₃Si₅ decreases with the Nd substitution for La and we have analyzed this T_c dependence using Abrikosov and Gor'kov theory with crystal-field contributions. The estimated value of the interaction between the conduction electrons and the rare-earth spin (J_sf) is 37 meV which is adequate to suppress the coexistence of superconductivity and antiferromagnetism in La_2-xNd_xRh₃Si₅ alloys above 0.6 K. Finally, we have also analyzed the temperature dependence of the upper critical field of Nd-doped La₂Rh₃Si₅ alloys using a theory which incorporates spin-orbit coupling with an additional pair breaking parameter.