Interplay of spin-orbit torque and thermoelectric effects in ferromagnet/normal-metal bilayers

By C. Avci, Kevin Garello, M. Gabureac, Abhijit Ghosh, A. Fuhrer, S. Alvarado, Pietro Gambardella. 2014

313 citations recorded by the source corpus.

We present harmonic transverse voltage measurements of current-induced thermoelectric and spin-orbit torque (SOT) effects in ferromagnet/normal-metal bilayers, in which thermal gradients produced by Joule heating and SOT coexist and give rise to ac transverse signals with comparable symmetry and magnitude. Based on the symmetry and field dependence of the transverse resistance, we develop a consistent method to separate thermoelectric and SOT measurements. By addressing first ferromagnet/light-metal bilayers with negligible spin-orbit coupling, we show that in-plane current injection induces a vertical thermal gradient whose sign and magnitude are determined by the resistivity difference and stacking order of the magnetic and nonmagnetic layers. We then study ferromagnet/heavy-metal bilayers with strong spin-orbit coupling, showing that second harmonic thermoelectric contributions to the transverse voltage may lead to a significant overestimation of the antidamping SOT. We find that thermoelectric effects are very strong in Ta(6 nm)/Co(2.5 nm) and negligible in Pt(6 nm)/Co(2.5 nm) bilayers. After including these effects in the analysis of the transverse voltage, we find that the antidamping SOTs in these bilayers, after normalization to the magnetization volume, are comparable to those found in thinner Co layers with perpendicular magnetization, whereas the fieldlike SOTs are about an order of magnitude smaller.

Subfields: Atomic and Molecular Physics, and Optics, Biomedical Engineering, Condensed Matter Physics

View Paper: https://www.semanticscholar.org/paper/2b676ce25fcb157178b52d511f572b123b02cfd0

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In Atomic and Molecular Physics, and Optics

1. Pietro Gambardella
2. J. Sinova
3. T. Jungwirth
4. A. Manchon
5. G. Sala
6. I. Miron
7. Kevin Garello
8. A. Thiaville

In Condensed Matter Physics

1. J. Sinova
2. T. Jungwirth
3. Pietro Gambardella
4. I. Miron
5. Kevin Garello
6. J. Železný
7. A. Thiaville
8. G. Sala

Citations in the corpus

• Giant orbital Hall effect and orbital-to-spin conversion in 3d, 5d, and 4f metallic heterostructures (2022, methodology): “Current-induced spin-orbit torques were quantified by the harmonic Hall voltage method [40] using angle-scan measurements [51].”
• Current-induced spin-orbit torques in ferromagnetic and antiferromagnetic systems (2018, methodology): “Adapted from Avci et al. (2015b); Ghosh et al.”