Stray field and vortex controlled magnetoresistance in superconducting Bi/Ni bilayers

Highlights: • Tc of Bi/Ni is suppressed by stray field when magnetization switches. • MR hysteresis in Bi/Ni is related to vortex motion. • Bi/Ni bilayer presents both superconductivity and ferromagnetism. The magnetoresistance of superconducting Bi/Ni bilayers is investigated around the superconducting transition temperature. At temperatures within the superconducting transition, the magnetoresistance presents a superposition of symmetric peaks and hysteresis behaviors. The magnetoresistance peaks show the evidence of $T_C$ suppression due to stray fields from domain walls appearing during magnetization switching. The hysteresis behaviors show the effect of vortices motion on the superconductivity of Bi/Ni bilayers. This unusual magnetoresistance controlled by both stray fields and vortices provides a new understanding of the interaction between superconductivity and ferromagnetism in Bi/Ni bilayers.