Superconductivity, magnetism, and their coexistencein R(Ni1−xCox)2B2C (R=Lu, Tm, Er, Ho, Dy)

Abstract

The effect of Co substitution on superconductivity and magnetism in the system R(Ni1−xCox)2B2C (R = Lu, Tm, Er, Ho, Dy) is investigated by ac-susceptibility measurements in zero and applied magnetic fields and zero-field resistivity measurements. For all R series a rapid decrease of the superconducting transition temperature Tc is observed with increasing Co substitution, while the magnetic transition temperatures show only small changes. It is observed that the initial depression rate of Tc grows in magnitude in the R series from Lu to Ho. For the nonmagnetic system Lu(Ni1−xCox)2B2C the mechanisms leading to the decrease in Tc are analyzed and discussed. It was found that a transition from clean to dirty limit behavior occurs with Co doping. For the magnetic systems R(Ni1−xCox)2B2C R = Tm, Er, where antiferromagnetism and superconductivity coexist, the influence of Co doping results in the occurrence of anomalous behavior of ac-susceptibility, resistivity and the upper critical fields when Tc comes close to the magnetic transition temperatures TN. For Er(Ni1−xCox)2B2C reentrant-like behavior is observed, similar to that present in HoNi2B2C. The reentrant behavior of HoNi2B2C is enhanced with Co doping. Possible reasons for that behavior are discussed.

Source-reported materials — not catalogue approval

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