Transverse and Longitudinal Spin-Torque Ferromagnetic Resonance for Improved Measurements of Spin-Orbit Torques

Abstract

Spin-torque ferromagnetic resonance (ST-FMR) is a common method used to measure spin-orbit torques (SOTs) in heavy metal/ferromagnet bilayer structures. In the course of a measurement, other resonant processes such as spin pumping (SP) and heating can cause spin current or heat flows between the layers, inducing additional resonant voltage signals via the inverse spin Hall effect (ISHE) and Nernst effects (NE). In the standard ST-FMR geometry, these extra artifacts exhibit a dependence on the angle of an in-plane magnetic field that is identical to the rectification signal from the SOTs. We show experimentally that the rectification and artifact voltages can be quantified separately by measuring the ST-FMR signal transverse to the applied current (i.e., in a Hall geometry) in addition to the usual longitudinal geometry. We find that in Pt (6 nm)/CoFeB samples the contribution from the artifacts is small compared to the SOT rectification signal for CoFeB layers thinner than 6 nm, but can be significant for thicker magnetic layers. We observe a sign change in the artifact voltage as a function of CoFeB thickness that we suggest may be due to a competition between a resonant heating effect and the SP/ISHE contribution.

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Cited by in corpus (20)

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• Efficient generation of out-of-plane polarized spin current in polycrystalline heavy metal devices with broken electric symmetries
• Resolving Discrepancies in Spin-Torque Ferromagnetic Resonance Measurements: Lineshape vs. Linewidth Analyses
• A Perspective on Electrical Generation of Spin Current for Magnetic Random Access Memories
• Substrate-induced spin-torque-like signal in spin-torque ferromagnetic resonance measurement
• Anomalous sign inversion of spin-orbit torque in ferromagnetic/nonmagnetic bilayer systems due to self-induced spin-orbit torque
• Giant spin torque efficiency in naturally oxidized polycrystalline TaAs thin films
• Separation of Artifacts from Spin-Torque Ferromagnetic Resonance Measurements of Spin-Orbit Torque for the Low-Symmetry van der Waals Semi-Metal ZrTe${}_{\text{3}}$
• Estimation of spin-orbit torques in the presence of current-induced magnon creation and annihilation
• Interface enhanced helicity dependent photocurrent in metal/semimetal bilayers
• Enhancing z spin generation in trivial spin Hall materials for scalable, energy-efficient, field-free, complete spin-orbit torque switching applications
• Resonant Measurement of Non-Reorientable Spin-Orbit Torque from a Ferromagnetic Source Layer Accounting for Dynamic Spin Pumping
• RF field characterization and rectification effects in spin pumping and spin-torque FMR for spin-orbitronics
• Investigating spin and orbital effects via spin-torque ferromagnetic resonance
• Polar and quadratic magneto-optical Kerr effects in nonmagnetic/ferromagnet bilayers for spin-orbit torque measurements