Effect of Ferromagnet/Organic Semiconductor Interface Defect States on Tunnel Magnetoresistance of Hybrid Magnetic Tunnel Junctions

• Published in: physica status solidi (b) 2024-09, Vol.261 (9), p.n/a
• Main Authors: Sujatha, Yadlapalli, Pahuja, Abhishek, Deb, Debajit
• Format: Article
• Language: English
• Subjects: carrier injection; defect states; spin orientations; spin transfer torque; tunnel magnetoresistance; tunneling
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.202400059

Herein, analytical modeling of Fe3O4/x(≈1.1 nm)/Co (x = rubrene, C60, and bathocuproine (BCP)) magnetic tunnel junctions (MTJs) has been performed using rubrene, C60, and BCP as organic spacer layers. The simulation is considered as nonequilibrium Green's function assuming spin precession at ferromagnet/organic semiconductor (FM/OSC) interface defect states. The voltage‐dependent resistances for both parallel (RP) and antiparallel (RAP) orientations have been observed to be dependent on spin injection from FM/OSC defect states. Pinning well‐dependent defect state depths have been associated with band misalignment‐induced lattice distortion at FM/OSC interface of the devices. The large tunnel magnetoresistance (TMR) response for rubrene‐based MTJ device has been attributed to a higher change of FM/OSC defect state depths with voltage. High TMR may have reduced spin torque‐dependent spin precession, leading to lower spin transfer torque for the rubrene device. Hence, engineering of defect states at the FM/OSC interface may lead to the successful realization of enhanced TMR in organic spacer MTJs for high‐performance spintronic memory applications. In spite of small spin‐orbit coupling and hyperfine interactions, organic magnetic tunnel junctions suffer considerable tunnel magnetoresistance (TMR) quenching at room temperature (RT). Defect states in the form of pinning wells enhance coherent spin injection from those states thereby minimizing the RT TMR quenching process. Voltage‐dependent defect state distributions at ferromagnet/organic interface modify the spin injection process.