Distinguishing spin pumping from spin rectification in organic semiconductor-based lateral spin pumping device architectures

TL;DR

This paper demonstrates that in organic spintronics, in-plane angular measurements are essential to distinguish genuine spin transport signals from parasitic effects like spin rectification, revealing a new spurious inverse spin Hall effect in ferromagnets.

Contribution

It introduces a method using angular dependence to accurately separate spin signals from parasitic effects in organic spintronic devices, highlighting the importance of this approach for future research.

Findings

Linear power dependence and magnetic field inversion are insufficient to confirm spin transport.

Angular measurements can effectively distinguish pure spin signals from parasitic effects.

A novel spurious inverse spin Hall effect was observed in ferromagnetic materials.

Abstract

Over the last two decades organic spintronics has developed into a striving field with exciting reports of long spin diffusion lengths and spin relaxation times in organic semiconductors (OSCs). Easily processed and inexpensive, OSCs are considered a potential alternative to inorganic materials for use in spintronic applications. Spin currents have been detected in a wide range of materials, however, there is still uncertainty over the origin of the signals. Recently, we explored spin transport through an organic semiconductor with lateral spin injection and detection architectures, where the injected spin current is detected non-locally via spin-to-charge conversion in an inorganic detector. In this work we show that the widely-used control experiments like linear power dependence and inversion of the signal with the magnetic field are not sufficient evidence of spin transport and can lead to an incorrect interpretation of the signal. Here, we use in-plane angular dependent measurements to separate pure spin signal from parasitic effects arising from spin rectification (SREs). Apart from well established anisotropic magnetoresistance (AMR) and anomalous Hall effect (AHE), we observed a novel effect which we call spurious inverse spin Hall effect (ISHE). It strongly resembles ISHE behaviour, but arises in the ferromagnet rather than the detector meaning this additional effect has to be considered in future work.