Evolution of ground state and upper critical field in R(1-x)GdxNi2B2C (R = Lu, Y): Coexistence of superconductivity and spin-glass state

TL;DR

This study investigates how Gd3+ doping affects superconductivity and magnetic behavior in R(1-x)GdxNi2B2C compounds, revealing coexistence of superconductivity and spin-glass states and analyzing the evolution of critical fields.

Contribution

It provides new insights into the coexistence of superconductivity and spin-glass states in Gd-doped borocarbides, extending understanding within the Abrikosov-Gor'kov framework.

Findings

Superconducting transition temperature decreases with Gd doping.

A region of coexistence of superconductivity and spin-glass state is identified.

Upper critical field behavior changes qualitatively with doping.

Abstract

We report effects of local magnetic moment, Gd3+, doping (x =< 0.3) on superconducting and magnetic properties of the closely related Lu(1-x)GdxNi2B2C and Y(1-x)GdxNi2B2C series. The superconducting transition temperature decreases and the heat capacity jump associated with it drops rapidly with Gd-doping; qualitative changes with doping are also observed in the temperature-dependent upper critical field behavior, and a region of coexistence of superconductivity and spin-glass state is delineated on the x - T phase diagram. The evolution of superconducting properties can be understood within Abrikosov-Gor'kov theory of magnetic impurities in superconductors taking into account the paramagnetic effect on upper critical field with additional contributions particular for the family under study.