Giant coercivity enhancement and dimensional crossover of superconductivity in Co2FeSi-NbN nanoscale bilayers

Abstract

Proximity coupling and magnetic switching dynamics are shown to be correlated in bilayers of fully spin polarized ferromagnet (F) Co2FeSi and superconductor (S) NbN. The upper critical field derived from resistivity measurements shows a dimensional crossover with a reduced effective thickness of the S layer. At temperatures (T) ≪ superconducting Tc, the measured M-H loops show two step switching: one at T-independent value ∼7 Oe and other at strongly T-dependent value becoming very large ∼1 kOe at 2 K. These results reveal induced ferromagnetism in S-layer at the S/F interface with vortex pinning influenced dynamics. This research has been supported by Council of Scientific and Industrial Research and Department of Science and technology (DST) Government of India. R.C.B. acknowledges J. C. Bose National fellowship of the DST.