Organic semiconductor spacer thickness-dependent interface defect state spin injection across tunnel magnetoresistance devices

This study investigates the effect of organic spacer layer thickness on spin transport in magnetic tunnel junctions (MTJs) of the form $$\hbox {Fe}_{3}\hbox {O}_{4}$$ Fe 3 O 4 /x/Co (x=Rubrene, $$\hbox {C}_{60}$$ C 60 ) with Rubrene and $$\hbox {C}_{60}$$ C 60 as organic spacer layers. The simulation uses a nonequilibrium Green’s function, assuming spin precession at defect states at the ferromagnet/organic semiconductor interface. Parallel and antiparallel resistances have been observed to be thickness-independent at low thicknesses due to excellent magnetic coupling and minimal interfacial imperfections that eventually increased at high thicknesses. Drastic reduction of parallel and antiparallel currents at high-thickness regime has been attributed to the trapping of spins in deeper pinning wells with strong pinning strengthNotably, the rise in tunnel magnetoresistance with thickness is high in $$\hbox {Fe}_{3}$$ Fe 3 O $$_{4}$$ 4 /C $$_{60}$$ 60 /Co device compared to the $$\hbox {Fe}_{3}$$ Fe 3 O $$_{4}$$ 4 /Rubrene/Co device and has been attributed to the change in defect state depth with thickness and electron-predominant nature of $$\hbox {Fe}_{3}$$ Fe 3 O $$_{4}$$ 4 /C $$_{60}$$ 60 /Co device. Therefore, engineering of spacer layer thickness-dependent spin transport in MTJs resulted in successful implementation of organic spacer MTJs for high-performance spintronic memory applications. Graphic abstract