|
Journal of Physical Studies 5(3/4), 335–340 (2001)
DOI: https://doi.org/10.30970/jps.05.335 MAGNETIC IMPURITIES IN THE BOROCARBIDE YNi2B2CM. Willner, S. Manalo{1}, H. Michor, M. El-Hagary, G. Hilscher
Institut für Experimentalphysik, Technische
Universität Wien, 1040 Wien, Austria. |
 |
Measurements of the specific heat and the magnetization on the quaternary borocarbides $R$Ni$_2$B$_2$C ($R=$Gd, Er, and Ho) show that the critical temperature $T_c$ scales roughly with the DeGennes factor $(g_J - 1)^2 J(J+1)$. In GdNi$_2$B$_2$C superconductivity is suppressed by magnetic pair-breaking, whereas in the systems Y$_{1-x}$Er$_x$Ni$_2$B$_2$C and Y$_{1-x}$Ho$_x$Ni$_2$B$_2$C superconductivity and magnetism coexist within the whole range of $0 \leq x \leq 1$. For $R$Ni$_2$B$_2$C with $R=$ Er, Ho and Dy one can show that the coherence length $ξ(0)$ is larger than the lattice parameters of the system, so that the magnetic ions act on the Cooper pairs. Measurements on (Y,$R$)Ni$_2$B$_2$C show that the variation of the specific heat jump $Δ C(T_c)$ vs. $T_c$ roughly scales with the Abrikosov-Gor'kov theory for highly diluted systems [1]. Due to these features of the (Y,$R$)Ni$_2$B$_2$C system, and the fact that it can be very well described by the Eliashberg theory [2], calculations were done to test whether the systems with $R=$ Er, Ho, Dy, Gd and Yb can simply be described by YNi$_2$B$_2$C including magnetic impurities. The calculations show that the model works well for $x \ll 1$.\par
PACS number(s): 74.25.Bt, 74.70.Dd, 74.62.Yb, 74.20.-z