SUPERCONDUCTIVITY-INDUCED PINNING EFFECT IN SUPERCONDUCTOR/MAGNETIC TUNNEL JUNCTIONS

We have fabricated Nb/magnetic tunnel junction (MTJ) structure to investigate superconductivity-induced impact on magnetization states of the proximal ferromagnet. By sweeping temperature in a parallel or antiparallel magnetization state, a thermal hysteresis in MTJ resistance was observed at temperature below the Nb superconducting critical temperature (Tc). In the parallel configuration, a Barkhausen-like jump in junction resistance arises when the magnetization of free layer is close to switching from parallel to antiparallel configuration. We attribute the hysteresis and Barkhausen-like jump to the pinning effect of Nb on the proximal magnetic domains and estimate the magnitude of the moment change of the free layer responsible for the resistance change resulting from Barkhausen-like jump.