Spin dependent transport and magnetic properties in Fe4N/tris(8-hydroxyquinoline) aluminum/Co organic spin valves fabricated by facing-target sputtering

Abstract

Spin-dependent electronic transport and magnetic properties of Fe4N/tris(8-hydroxyquinoline) aluminum (Alq3)/Co organic spin valves (OSVs) are investigated. Fe4N/Alq3/Co OSVs with different Alq3 thicknesses t exhibit an inverse magnetoresistance (MR), which comes from the opposite effective spin polarization at the two ferromagnetic electrode/Alq3 interfaces. For the antiparallel configurations, MR at 3K presents the obvious asymmetry, corresponding to the asymmetric hysteresis loop. The asymmetric loops of magnetization and MR can be attributed to the magnetic coupling at the Alq3/Co interface. The interfacial diffusion between Co and Alq3 is weak due to the advantages of facing-target sputtering. Below 120nm, MR increases with the increased t owing to the decreased effect of the ill-defined layer. The reduced MR at 260nm is ascribed to the decline of spin polarization.