Organic semiconductors are characterized by a very low spin–orbit interaction, which, together with their chemical flexibility and relatively low production costs, makes them an ideal materials system for spintronics applications. The first experiments on spin injection and transport occurred only a few years ago, and since then considerable progress has been made in improving performance as well as in understanding the mechanisms affecting spin-related phenomena. Nevertheless, several challenges remain in both device performance and fundamental understanding before organic semiconductors can compete with inorganic semiconductors or metals in the development of realistic spintronics applications. In this article we summarize the main experimental results and their connections with devices such as light-emitting diodes and electronic memory devices, and we outline the scientific and technological issues that make organic spintronics a young but exciting field.

Spin routes in organic semiconductors

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Spin Routes in Organic Semiconductors

Molecular spintronics is recognized to as an attractive new research direction in a field of spintronics, following to metallic spintronics and inorganic semiconductor spintronics, and attracts many people in recent decades The purpose of this manuscript is to describe the history of molecular spintronics by introducing important achievements and to show the current status of this field In addition, the authors briefly introduce several theories for implementing studies in molecular spintronics

Molecular Spintronics

The first decade of organic spintronics research

Organic spintronics is an emerging and potential platform for future electronic devices. Significant progress has been made in understanding the spin injection, manipulation, and detection in organic spin valves in the past decade plus since its discovery. Studies have also been advanced to a range of materials combination of organic semiconductors and ferromagnetic electrodes for improving their performance especially at high temperatures. In addition, there are several remarkable studies on development of the spin valves as a multifunctional device. However, the research in this field is still in its infancy and there is a need to resolve many issues which keep this field far away from applications. In this report, we review major advances in organic spin valves such as understanding the underlying physics in spin injection and transport, high temperature operations, and functionality. We also highlight some of the outstanding challenges in this promising research field. Finally, we suggest an outlook on the future of organic spintronics.

Organic Spin Valves: A Review

The spin injection and transport properties of low-molecular-weight organic semiconductors such as pentacene and bis(l,2,5-thiadiazolo)-p-quinobis(l,3-dithiole) (BTQBT) were investigated utilizing planar-type spin-valve devices with half-metallic La0.67Sr0.33MnO3 electrodes. The devices showed clear spin-valve characteristics with a magnetoresistance (MR) ratio of up to 29% at 5K. The MR ratio was found to depend on the gap spacing of the electrodes, the applied bias voltage, temperature, and the crystallinity of the films. It was also affected by gas adsorption onto the films, indicating that the spins were scattered by carriers and/or radical ions in the films generated through charge transfer from gas molecules.

Planar-type spin valves based on low-molecular-weight organic materials with La0.67Sr0.33MnO3 electrodes

We have prepared layered sandwich structures composed of Co / organic materials / La 0.67 Sr 0.33 MnO 3 and measured the magnetic field effect on electrical resistance. We inserted various OMs including pentacene, C 60 , 8-hydroxy-quinoline aluminum and titanyl-phthalocyanine with a thickness in the range from 200 nm to 1,000 nm. All devises prepared showed clear spin-valve characteristics with magneto-resistance (MR) ratios of approximately a few to 10% at low temperature. It was found that spins were transported in rather thick organic films, and the polarity of MR depended upon materials inserted and their film thickness.

Magnetoresistance in Spin Valves Based on Organic Semiconductors with Ferromagnetic Electrodes

Spin injection and transport characteristics of low-molecular-weight organic semiconductors such as pentacene and bis(l,2,5-thiadiazolo)-p-quinobis(l,3-dithiole) (BTQBT) have been studied utilizing lateral type spin-valve devices with half metal electrodes, LaA0.67Sr0.33MnO3 (LSMO). The LSMO electrodes with a spacing of 200 nm were prepared by electron-beam lithography and dry etching of the epitaxial films grown on MgO substrates. The devices showed clear spin-valve behaviors with a magneto-resistance (MR) ratio up to 29 % at 9.1K. It was found that the MR ratio depended on the crystallinity of organic films as well as on temperature and applied bias voltages

Tomonori Ikegami

Papers

Planar-type spin valves based on low-molecular-weight organic materials with La0.67Sr0.33MnO3 electrodes

Magnetoresistance in Spin Valves Based on Organic Semiconductors with Ferromagnetic Electrodes

Preparation of Lateral Organic Spin-valve Devices with La0.7Sr0.3MnO3