Effect of magnetic transition-metal impurities on the tunnel characteristics of superconducting contacts

Singularities in the derivatives of the tunnel-current amplitudes in SIS' junctions are studied for the case when the superconductors constituting the junction contain magnetic transition-metal impurities. It is shown that with a forbidden energy band between the impurity band and the energy continuum the second and higher derivatives of the tunnel-current amplitudes have singularities in addition to those predicted by the Abrikosov–Gor’kov theory.