Effect of Spacer Layer Thickness on Interface Defect-Dependent Spin Injection in Organic Magnetic Tunnel Junctions

In this article, we have theoretically investigated spacer-thickness-dependent spin transport across organic magnetic tunnel junctions (MTJs) [x/Rubrene/Co, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${x} =$ </tex-math></inline-formula> La2O3, LaMnO3, La0.7Ca0.3MnO3 (LCMO), La0.7Sr0.3MnO3 (LSMO)] using non equilibrium Green’s function (NEGF). Parallel and antiparallel resistances have been found to be thickness-independent due to high magnetic coupling and minimum interfacial defects at low thickness region. Sharp rise of differential antiparallel resistance in La2O3 device has been attributed to large change in defect state depth with spacer thickness. Saturation of spin current at large spacer thickness has been attributed to trapping of spins at large defect depths with strong pinning strength. Spacer thickness modifies magnetic coupling between electrodes thereby modulating tunnel magnetoresistance (TMR) response across the devices. Reduction of spin transfer torque (STT) with thickness resulted in spin damping thereby quenching TMR response across the devices.