Study of Exchange Bias in All Ferromagnetic Fe/Co Soft/Hard Bilayer

We report the unusual and exotic phenomenon of positive exchange bias observed in all ferromagnetic layered soft/hard Fe/Co spring magnet systems. Interestingly, the results are well reproducible both at low (5 K) and room temperatures (300 K). The effect of applied magnetic pinning field of 7 and -5 T reveals a noticeable shift of magnetic hysteresis loops along the field direction. We argue that the reason behind observed positive exchange bias is the establishment of antiferromagnetic (AFM) exchange coupling at the interface as a result of intermixing of Fe into the Co layer. The collective coupling of this intermix layers is AFM which facilitates positive shift of magnetic hysteresis loop.