Superconductivity and magnetism in R(Ni1−xFex)2B2C (R = Er and Tm) systems

The effect of Fe substitution on structure, superconductivity and magnetism in the R(Ni1−xFex)2B2C (R = Er and Tm) systems are systematically studied by means of X-ray diffraction, transport properties and heat capacity measurements. The crystal structure is almost unchanged upon the iron substitutions. A rapidly decrease of Tc is observed in both the systems, and disappeared around x = 0.06 for R = Er, and x = 0.08 for R = Tm. TN almost unchanged in the concentration range from x = 0 to x = 0.1 for R = Er. The effective magnetic moments μeff which were obtained by the Curie–Weiss law from the magnetic temperature dependence data were almost unchanged with x, respectively. Based on the results of susceptibility, specific heat and previous reported, it can be concluded that the substitution of Fe for Ni maybe similar to that of Co case which can be treated as non-magnetic impurities and the decreases of N(EF) is the main reason for the decrease of Tc.