Studying pure spin currents in weakly spin-orbit coupled materials using the pulsed ferromagnetic resonance driven inverse spin-Hall effect (Conference Presentation)

Spin-orbit coupling (SOC) and the spin diffusion length in condensed matter are crucial parameters for spintronics applications. In order to study these, we have succeeded in employing a pulsed spin-pumping method based on ferromagnetic resonance (FMR) to generate pure spin currents from ferromagnetic (FM) substrates into non-FM semiconductor layers1 which can then be detected through the inverse spin-Hall effect (ISHE). When the FM is in FMR with a pulsed microwave (MW) excitation, a pure spin-current is generated in the non-FM layer which can circumvent potential impedance mismatches between the FM and the non-FM layer and, therefore generate a strong pulsed ISHE signal. Due to the low duty cycle of the pulsed excitation, MW excitation powers can be used that are strong enough to generate pronounced ISHE signals even in materials with weak SOC such as carbon-based materials. This sensitivity allows for the study of the quantitative nature of the ISHE and thus, to apply scrutiny to a number of questions about the ISHE effect in general, including how strongly FMR-driving field inhomogeneities affect a measured ISHE current, the relationship of ISHE voltages to the ISHE current in devices consisting of layers with different conductivities, as well the experimental conditions which have to be monitored during an ISHE experiment in order to ensure reproducibility. This work was supported by the National Science Foundation (DMR-1404634 – Sample preparation and Experiments) and the NSF-Material Science & Engineering Center (DMR-1121252- Polymer Synthesis and Facilities) at the University of Utah. 1. D. Sun et al., Nature Materials 15, 863–869 (2016). doi:10.1038/nmat4618