Pair‐Breaking and Magnetic Ordering in the Pseudo‐Quaternary Intermetallic Series (Y, Gd)Ni 2 B 2 C

Alloying influences on the superconducting and magnetic properties of the (Gd x Y 1− x )Ni 2 B 2 C series are studied. For x < 0.25, T c is degraded linearly with x as expected from the theory of Abrikosov‐Gorkov. Magnetization and magnetoresistivity measurements for x = 0.22 show that the magnetic saturation is attained only for fields as high as 80 kOe implying that even for such a low Gd concentration, antiferromagnetic couplings are quite strong. On the other hand, the magnetic dilution in the Heisenberg antiferromagnet GdNi 2 B 2 C causes a linear depression of the magnetic ordering temperatures as expected from molecular field theory. The abrupt quench of superconductivity for x > 0.25 and the coexistence of superconductivity with long‐range antiferromagnetic order for 0.1 < x < 0.25 are discussed.