Depression of T-c by nonmagnetic impurities in antiferromagnetic superconductor with T-c < T-N

Theoretical considerations show that nonmagnetic impurities (which in conve ntional superconductors are not expected to have much influence on T-c) sho uld depress T-c in antiferromagnetic superconductors with T-c less than T-N DyNi2B2C (T-c = 6.5 K, T-N = 11 K) and ErNi2B2C (T-c = 10.5 K, T-N = 6.5 K ) form an ideal pair of antiferromagnetic superconductors, with T-c less th an T-N and T-c greater than T-N, respectively, to investigate this effect e xperimentally which is the aim of the present work. Our most important find ing is that in Y1-xDyxNi2B2C, dilute substitution of Y results in a decreas e of T-c (Delta T-c similar to -2.5 K for x = 0.9) in direct contrast to Y1 -xErxNi2B2C, where substitution of Y results in an increase of T-c (Delta T -c similar to +0.3 K for x = 0.9). Although depression of T-c in DyNi2B2C b y nonmagnetic Lu ions has been reported, that report did not consider the a bove-mentioned theoretical consideration. Our work points out the importanc e of nonmagnetic impurities in magnetic superconductors. (C) 1999 Elsevier Science B.V. All rights reserved.