Measurements of interfacial spin-polarization of ferromagnetic materials with the use of epitaxial NbN junctions

Abstract

Epitaxial NbN/ferromagnetic material (Co and Co₂MnGe) multilayers have been grown on MgO (100) substrate and the spin polarization of the ferromagnetic materials has been investigated by using the multilayer junctions. The Co₂MnGe layers have been deposited on MgO//NbN and the inverted structure (NbN layers on Co₂MnGe films) has been also made. The epitaxial relationship between NbN and Co₂MnGe layers with an in-plane 45°rotation was confirmed for the two types of multilayer structures. Andreev reflection measurements on these junctions and the modified Blonder-Tinkham-Klapwijk (BTK) analysis have shown that the spin polarization values of Co and Co₂MnGe are 0.38 and 0.51, respectively. These values are in good agreement with previous data obtained by using the point-contact Andreev reflection (PCAR) technique. The results suggest the potential of the epitaxial NbN junction method as a measurement technique of spin polarization.