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arXiv · 1611.05798

Inductive detection of field-like and damping-like AC inverse spin-orbit torques in ferromagnet/normal metal bilayers

Andrew J. Berger·Eric R. J. Edwards·Hans T. Nembach·Alexy D. Karenowska·Mathias Weiler·Thomas J. Silva
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Abstract

Functional spintronic devices rely on spin-charge interconversion effects, such as the reciprocal processes of electric field-driven spin torque and magnetization dynamics-driven spin and charge flow. Both damping-like and field-like spin-orbit torques have been observed in the forward process of current-driven spin torque and damping-like inverse spin-orbit torque has been well-studied via spin pumping into heavy metal layers. Here we demonstrate that established microwave transmission spectroscopy of ferromagnet/normal metal bilayers under ferromagnetic resonance can be used to inductively detect the AC charge currents driven by the inverse spin-charge conversion processes. This technique relies on vector network analyzer ferromagnetic resonance (VNA-FMR) measurements. We show that in addition to the commonly-extracted spectroscopic information, VNA-FMR measurements can be used to quantify the magnitude and phase of all AC charge currents in the sample, including those due to spin pumping and spin-charge conversion. Our findings reveal that Ni$_{80}$Fe$_{20}$/Pt bilayers exhibit both damping-like and field-like inverse spin-orbit torques. While the magnitudes of both the damping-like and field-like inverse spin-orbit torque are of comparable scale to prior reported values for similar material systems, we observed a significant dependence of the damping-like magnitude on the order of deposition. This suggests interface quality plays an important role in the overall strength of the damping-like spin-to-charge conversion.

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Andrew J. Berger, Eric R. J. Edwards, Hans T. Nembach, Alexy D. Karenowska, Mathias Weiler, Thomas J. Silva. 2017-10-26. Inductive detection of field-like and damping-like AC inverse spin-orbit torques in ferromagnet/normal metal bilayers. https://doi.org/10.1103/physrevb.97.094407

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