Effects of Tm substitution on superconductivity and magnetism in the antiferromagnetic borocarbide superconductor Dy_1-x Tm _xNi₂B₂C

A series of single-phased Dy_1-x Tm_xNi ₂B₂C (x=0-1) compounds were prepared by an arc-melting method. The superconductivity and magnetic properties have been investigated by measuring electrical resistivity, magnetization, and specific heat. The superconducting transition temperature T_c decreases rapidly with increasing x, and shows a minimum around x=0.15, then increases gradually with a further increase in x. The magnetic transition temperature T_M gradually decreases with increasing x. The effective magnetic moment μ_eff gradually decreases with increasing x and agrees with the estimation assuming the free ion values of Dy³⁺ and Tm³⁺ states, indicating that the change in the electronic structure of Dy and Tm ions is very small. The present results together with previously reported Dy _1-x R_x Ni₂ B₂ C (R=Ho, Tb, Y, and Lu) systems were discussed and well explained in the frame of Abrikosov and Gor'kov theory and the field cancellation effect at Ni sites.