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Inverse spin Hall effect from pulsed spin current in organic semiconductors with tunable spin–orbit coupling

Abstract

Exploration of spin currents in organic semiconductors (OSECs) induced by resonant microwave absorption in ferromagnetic substrates is appealing for potential spintronics applications. Owing to the inherently weak spin–orbit coupling (SOC) of OSECs, their inverse spin Hall effect (ISHE) response is very subtle; limited by the microwave power applicable under continuous-wave (cw) excitation. Here we introduce a novel approach for generating significant ISHE signals in OSECs using pulsed ferromagnetic resonance, where the ISHE is two to three orders of magnitude larger compared to cw excitation. This strong ISHE enables us to investigate a variety of OSECs ranging from π-conjugated polymers with strong SOC that contain intrachain platinum atoms, to weak SOC polymers, to C60 films, where the SOC is predominantly caused by the curvature of the molecule’s surface. The pulsed-ISHE technique offers a robust route for efficient injection and detection schemes of spin currents at room temperature, and paves the way for spin orbitronics in plastic materials.

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Figure 1: Detection of pulsed spin current through the p-ISHE response.
Figure 2: Electroluminescence spectra of the Pt-polymer series studied here, and observation of the p-ISHE response in Pt-1 polymer.
Figure 3: p-ISHE(B) response in various OSEC materials with tunable spin–orbit coupling.
Figure 4: p-ISHE(B) responses versus the OSEC thickness.

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Acknowledgements

We acknowledge support by the National Science Foundation (DMR-1404634) for sample preparation, execution of the experiments and data processing of the ISHE experiments. We also acknowledge the NSF-Material Science & Engineering Center (DMR-1121252) for supporting Pt-polymer synthesis, execution of the OSV experiments and development of the ISHE device structures, as well as support for the device preparation facilities.

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Contributions

D.S., K.J.v.S., C.B. and Z.V.V. conceived this study and the experiments. D.S. fabricated the devices. K.J.v.S., D.S. and H.M. implemented the p-ISHE set-up. K.J.v.S., H.M. and M.K. measured the p-ISHE response; D.S., M.K. and C.Z. measured the device conductivity and capacitance. C.Z. and D.S. measured the Pt-polymer electroluminescence spectra. M.G. measured the frequency dependence of the FMR spectra. D.S. carried out the circuit modelling for the p-ISHE current. C.B. and Z.V.V. were responsible for the project planning, group management, and final writing of the manuscript . All authors discussed the results, and worked on data analysis and manuscript preparation.

Corresponding authors

Correspondence to Christoph Boehme or Z. Valy Vardeny.

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The authors declare no competing financial interests.

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Sun, D., van Schooten, K., Kavand, M. et al. Inverse spin Hall effect from pulsed spin current in organic semiconductors with tunable spin–orbit coupling. Nature Mater 15, 863–869 (2016). https://doi.org/10.1038/nmat4618

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