The effects of chromium and manganese on the superconducting density of states of niobium and vanadium
We have made proximity effect electron tunneling measurements on Nb-Cr, Nb-Mn, V-Cr, and V-Mn films. These films were prepared in an MBE system and in the case of the V films they were grown epitaxialy on sapphire substrates. When the data for Nb are compared to Shiba's theory for magnetic dopants in superconductors, we see no states which are localized in energy as Shiba predicts although there is some indication that there are some states in the gap which are smeared out. For V there are no indications of any states in the gap suggesting that low concent rations of Mn and Cr are not magnetic in V. We have also looked at the smearing of the gap edge present in the I-V charateristics of our pure Nb sample. We have seen that the degree of smearing of the gap edge is consistant with surface impedance measurements on Nb, and that it can be related to the fact that the density of state at the Fermi energy in Nb lies on the side of a very sharp peak in the density of states.
chromium, manganese, niobium, vanadium, superconducting density, proximity effect electron tunneling
University of Illinois - Urbana-Champaign
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