Despite their great promise for providing a pathway for very efficient and fast manipulation of magnetization, spin‐orbit torque (SOT) operations are currently energy inefficient due to a low damping‐like SOT efficiency per unit current bias, and/or the very high resistivity of the spin Hall materials. This work reports an advantageous spin Hall material, Pd1−
Giant bulk spin–orbit torque and efficient electrical switching in single ferrimagnetic FeTb layers with strong perpendicular magnetic anisotropy
Efficient manipulation of antiferromagnetically coupled materials that are integration-friendly and have strong perpendicular magnetic anisotropy (PMA) is of great interest for low-power, fast, dense magnetic storage and computing. Here, we report a distinct, giant bulk damping-like spin–orbit torque in strong-PMA ferrimagnetic Fe 100− x Tb x single layers that are integration-friendly (composition-uniform, amorphous, and sputter-deposited). For sufficiently thick layers, this bulk torque is constant in the efficiency per unit layer thickness, [Formula: see text]/ t, with a record-high value of 0.036 ± 0.008 nm −1 , and the damping-like torque efficiency [Formula: see text] achieves very large values for thick layers, up to 300% for 90 nm layers. This giant bulk torque by itself switches tens of nm thick Fe 100− x Tb x layers that have very strong PMA and high coercivity at current densities as low as a few MA/cm 2 . Surprisingly, for a given layer thickness, [Formula: see text] shows strong composition dependence and becomes negative for composition where the total angular momentum is oriented parallel to the magnetization rather than antiparallel. Our findings of giant bulk spin torque efficiency and intriguing torque-compensation correlation will stimulate study of such unique spin–orbit phenomena in a variety of ferrimagnetic hosts. This work paves a promising avenue for developing ultralow-power, fast, dense ferrimagnetic storage and computing devices.
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- Award ID(s):
- 1719875
- PAR ID:
- 10325362
- Date Published:
- Journal Name:
- Applied Physics Reviews
- Volume:
- 9
- Issue:
- 2
- ISSN:
- 1931-9401
- Page Range / eLocation ID:
- 021402
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Spin-orbit torques (SOTs) have been widely understood as an interfacial transfer of spin that is independent of the bulk properties of the magnetic layer. Here, we report that SOTs acting on ferrimagnetic Fe x Tb 1- x layers decrease and vanish upon approaching the magnetic compensation point because the rate of spin transfer to the magnetization becomes much slower than the rate of spin relaxation into the crystal lattice due to spin-orbit scattering. These results indicate that the relative rates of competing spin relaxation processes within magnetic layers play a critical role in determining the strength of SOTs, which provides a unified understanding for the diverse and even seemingly puzzling SOT phenomena in ferromagnetic and compensated systems. Our work indicates that spin-orbit scattering within the magnet should be minimized for efficient SOT devices. We also find that the interfacial spin-mixing conductance of interfaces of ferrimagnetic alloys (such as Fe x Tb 1- x ) is as large as that of 3 d ferromagnets and insensitive to the degree of magnetic compensation.more » « less
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Abstract Spin‐orbit torques generated by exfoliated layers of the low‐symmetry semi‐metal ZrTe3are measured using the spin‐torque ferromagnetic resonance (ST‐FMR) technique. When the ZrTe3has a thickness greater than about 10 nm, artifacts due to spin pumping and/or resonant heating can cause the standard ST‐FMR analysis to overestimate the true magnitude of the torque efficiency by as much as a factor of 30, and to indicate incorrectly that the spin‐orbit torque depends strongly on the ZrTe3layer thickness. Artifact‐free measurements can still be achieved over a substantial thickness range by the method developed recently to detect ST‐FMR signals in the Hall geometry as well as the longitudinal geometry. ZrTe3/Permalloy samples generate a conventional in‐plane anti‐damping spin torque efficiency = 0.014 ± 0.004, and an unconventional in‐plane field‐like torque efficiency = 0.003 ± 0.001. The out‐of‐plane anti‐damping torque is negligible. It is suggested that artifacts similarly interfere with the standard ST‐FMR analysis for other van der Waals samples thicker than about 10 nm.
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0087260
