Driving field amplitude gauged quantitative inverse spin Hall effect detection

TL;DR

This paper presents a method for precise, in situ measurement of the FMR driving field amplitude using EPR-induced transient nutation of BDPA molecules, improving the quantitative accuracy of inverse spin Hall effect detection in thin films.

Contribution

It introduces a novel in situ monitoring technique for the FMR driving field amplitude using BDPA molecules, enhancing the reproducibility and accuracy of ISHE measurements.

Findings

In situ B1 measurement via BDPA nutation frequency improves ISHE data accuracy.

Renormalization of ISHE voltage to B1^2 increases reproducibility.

Homogeneity of the FMR field affects measurement precision.

Abstract

Spin transport in thin-film materials can be studied by ferromagnetic resonantly (FMR) driven spin pumping of a charge-free spin current which induces an electromotive force through the inverse spin Hall effect (ISHE). For quantitative ISHE experiments, precise control of the FMR driving field amplitude $B_1$ is crucial. This study exploits in situ monitoring of $B_1$ by utilization of electron paramagnetic resonantly (EPR) induced transient nutation of paramagnetic molecules (a 1:1 complex of {\alpha},{\gamma}-bisdiphenylene-{\beta}-phenylallyl and benzene, BDPA) placed as $B_1$ probe in proximity of a NiFe/Pt-based ISHE device. Concurrent to an ISHE experiment, $B_1$ is obtained from the inductively measured BDPA Rabi-nutation frequency. Higher reproducibility is achieved by renormalization of the ISHE voltage to $B_1^2$ with an accuracy that is determined by the homogeneity of the FMR driving field and thus by the applied microwave resonator and ISHE device setup.