Multiple 0-π transitions in superconductor/insulator/ferromagnet/superconductor Josephson tunnel junctions

We report on experimental studies about superconducting coupling through a thin Ni76Al24 film. A patterning process has been developed, which allows in combination with the wedge shaped deposition technique the in situ deposition of 20 single Nb∕Al∕Al2O3∕Ni3Al∕Nb multilayers, each with its own well-defined Ni3Al thickness. Every single multilayer consists of 10 different sized Josephson junctions, showing a high reproducibility and scaling with its junction area. Up to six damped oscillations of the critical current density against F-layer thickness were observed, revealing three single 0-π transitions in the ground state of Josephson junctions. Contrary to former experimental studies, the exponential decay length is one magnitude larger than the oscillation period defining decay length. The theoretical predictions based on linearized Eilenberger equations results in excellent agreement of theory and experimental results.