Josephson effect in MgB2∕Pd∕Fe∕Nb Josephson junctions

Abstract

MgB 2 ∕ Pd ∕ Fe ∕ Nb Josephson junctions were fabricated and characterized. The junctions exhibited the Josephson effect. A supercurrent was observed across the magnetically active layer formed at the Pd and Fe interface and also across the magnetic metal Fe itself. Shapiro steps and fractional Shapiro steps were observed when microwave fields were applied to the junctions. Modulation of the critical currents of the junctions was observed when an external magnetic field was applied in the plane of the junctions. The maxima of the magnetic field dependence of the critical current (Ic−B) did not occur at zero fields but at small positive fields of about 3.7μT. The magnetic field of 3.7μT increased the critical current by 100% when it was applied in the plane of the junction or perpendicular to the junction plane. The effect disappeared when the polarity of the field was reversed.

Fabrication of Planar Sandwich Type Josephson Junctions Using ${\rm MgB}_{2}$ Thin Film With a Nb Counter Electrode

“…Technologies to produce high quality superconducting thin films and Josephson junctions are prerequisites for such purpose. To this end, various types of Josephson elements have been developed [2]- [14]. Among those are point contact junctions by Zhang et al [2], nanobridges by Brinkmann et al [3], ion damaged weak links by Burnell et al [4] and also by Cybart et al [5], and thin film multilayer junctions [6]- [14].…”

“…Shimakage [12] reported all junctions with an AlN barrier layer. Kye et al reported a proximity junction with Ag as the barrier [13] and Malisa fabricated junctions with a Pd/Fe ferromagnetic barrier [14].…”