Magnetoresistance effect in organic magnetic junctions using spin filters

Magnetoresistance effect in organic magnetic junctions using spin filters
K.V.Raman장준연J.S. Moodera
spin filter; rubrene; magnetoresistance
Issue Date
55th Annual Conference on Magnetism and Magnetic Materials
Increasing the spin injection efficiency is critical to the success of spin transport through organic semiconductor (OS) towards developing organic spintronics. Efforts are currently under way to improve the interface properties to achieve this. Our earlier work on rubrene barrier based magnetic junctions (MTJs) using conventional ferromagnetic electrodes has shown the important role of interfaces in spin injection processes and the weakening interfacial magnetic behavior[1, 2]. Another novel approach is to apply spin filter phenomena for obtaining high degree of spin polarized current into the OS. In this regard, we have recently performed spin transporstudies using EuS spin filter barrier to inject spin-polarized current into rubrene. EuS is a ferromagnetic semiconductor capable of providing greater than 90% spin polarized current below its critical temperature (~16.6K) [3]. Tunnel junctions Al/EuS/Rubrene/Fe and Al/EuS/Rubrene/Al2O3/Fe were fabricated for spin transport measurements at low temperature. Magnetoresistance (MR) has been obseved at high these devices by changing the relative magnetization orientations of EuS and Fe. Unlike, other spin valve devices and conventional MTJs, the MR was found to increase with bias. A maocirnum in MR of ~3% is observed at high biases (~1.5V) in our samples. This has been attributed to the improved spin injection efficiency due to Flowler-Nordheim tunneling [3, 4]. Current results show promise to engineer the interface with OS to achieve higher spin injection efficeincy at high voltage biases. Furthemore, this shows that with the usage of spin filters it may be possible to electrically inject highly spin polarized current for investigating its dependence on the optical excitations in organinc light emitting diodes. In this talk these will be addressed. This work was supported by grants from ONR, NSF and KIST-MIT project.
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