Quantitative inverse spin Hall effect detection under control of the ferromagnetic resonant driving field amplitude*

Charge-free spin current from a ferromagnetic (FM) into a non-magnetic material is possible under FM resonance (FMR), and this can be observed through spin- to charge-current conversion using the inverse spin Hall effect (ISHE) [1,2]. As the magnitude of the ISHE scales linearly with the power associated with the FMR driving field amplitude~$B_{\mathrm{1}}$, quantitative ISHE measurements require precise control of~$B_{\mathrm{1}}$. This study demonstrates in~\textit{situ}~monitoring of~$B_{\mathrm{1}}$~by electron paramagnetic resonantly induced transient nutation of paramagnetic molecules (1:1complex of $\alpha $, $\gamma $-bisdiphenylene- $\beta $-phenylallyl and benzene, BDPA) placed in proximity of an NiFe/Pt-based ISHE device. Concurrent to an ISHE experiment,~$B_{\mathrm{1}}$~is obtained from the inductively measured BDPA Rabi-nutation frequency. High reproducibility of the ISHE measurement is achieved using this approach combined with the renormalization of the ISHE voltage to~$B_{\mathrm{1}}^{\mathrm{2}}$, with an accuracy limited only by the inhomogeneity of the FMR driving field [3]. [1] K. Ando, at al.,~\textit{J. Appl. Phys.}~\textbf{109}, 103913 (2011). [2] D. Sun et al.,~\textit{Nat. Mater.~}\textbf{15~}863-869$~($2016). [3] M. Kavand et al., arXiv:1610.2759v1.