Spin-polarized quasiparticle tunneling in spin-filter pseudospin-valve devices

Abstract

Spin selective nature of spin-filter tunnel junctions can be integrated with conventional metallic ferromagnets to regulate spin polarized quasiparticles in superconducting devices. We report fabrication of pseudo spin-valve device made with a bilayer of nitride spin-filter tunnel barrier (DyN or GdN) and a transition metal ferromagnet (Co and Gd). We show resistance switching in these devices corresponding to parallel and antiparallel configuration of their mutual magnetization direction. With optimal deposition process partial nitridation of the Co layer can be achieved. The magnetically dead native CoN$_x$ layer at the Co-DyN interface acts the role of the barrier in these devices. In pseudo spin-valve with Co, lower resistance was found for antiparallel state compared to parallel configuration. Reverse resistance switching behavior was observed for the pseudo spin-valves with Gd. Presence of resistance switching in these devices further confirm the spin-filtering nature of DyN and GdN tunnel barrier. Quasiparticle transport at different temperatures in these devices was found to be compatible with conventional N-I-S tunnelling model. These devices can be further engineered to regulate spin polarized supercurrent in superconducting spintronics devices.