Josephson effect in tunnel junctions with vanadium and vanadium oxide

A study was made concerning the characteristics of the Josephson effect in V−VxOy−Pb tunnel junctions. The results reveal that the critical current Ic in zero field is anomalously low and corresponds to the conductivity of an S1−I−S2 channel in parallel with an N−I−S2 channel. The dependence of the critical current on the magnetic field intensity signifies a barrier layer which is very homogeneous in the junction plane. The anomalous Ic(T) characteristic as well as the temperature dependence of the period of Ic(H) oscillations suggests that the value of the order parameter in vanadium films near the barrier depends on the coordinates here. A comparison with the characteristics of V−Al−AlxOy−Pb junctions (with dAl ∼ 100 Å) indicates that the presence of vanadium oxide lowers the value of the superconducting order parameter in the vanadium film. The intrinsic step shape of the current-voltage characteristics is analyzed here and the corresponding parameters are used for independently determining the depth to which the magnetic film penetrates the vanadium film.

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