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

• Fe4N/Alq3/Co organic spin valves exhibit an inverse magnetoresistance.
• Asymmetric magnetoresistance is attributed to interfacial magnetic coupling.
• The advantages of facing-target sputtering make interfacial diffusion weak.

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 3 K 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 120 nm, MR increases with the increased t owing to the decreased effect of the ill-defined layer. The reduced MR at 260 nm is ascribed to the decline of spin polarization.