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Title: Temperature dependence of spin-orbit torques in W/CoFeB bilayers

Abstract

We report on the temperature variation of spin-orbit torques in perpendicularly magnetized W/CoFeB bilayers. Harmonic Hall voltage measurements in perpendicularly magnetized CoFeB reveal increased longitudinal and transverse effective magnetic field components at low temperatures. The damping-like spin-orbit torque reaches an efficiency of 0.55 at 19 K. Scanning transmission electron microscopy and X-ray reflectivity measurements indicate that considerable interface mixing between W and CoFeB may be responsible for strong spin-orbit interactions.

Authors:
; ; ; ;  [1]; ;  [2]; ; ;  [3]
  1. AGH University of Science and Technology, Department of Electronics, Al. Mickiewicza 30, 30-059 Kraków (Poland)
  2. NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto (Finland)
  3. Spintronics Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)
Publication Date:
OSTI Identifier:
22594311
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; COBALT BORIDES; EFFICIENCY; ELECTRIC POTENTIAL; INTERFACES; IRON BORIDES; LAYERS; L-S COUPLING; MAGNETIC FIELDS; MIXING; REFLECTIVITY; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0065-0273 K; TORQUE; TRANSMISSION ELECTRON MICROSCOPY; TUNGSTEN BORIDES; X RADIATION

Citation Formats

Skowroński, Witold, E-mail: skowron@agh.edu.pl, Cecot, Monika, Kanak, Jarosław, Ziętek, Sławomir, Stobiecki, Tomasz, Yao, Lide, Dijken, Sebastiaan van, Nozaki, Takayuki, Yakushiji, Kay, and Yuasa, Shinji. Temperature dependence of spin-orbit torques in W/CoFeB bilayers. United States: N. p., 2016. Web. doi:10.1063/1.4960793.
Skowroński, Witold, E-mail: skowron@agh.edu.pl, Cecot, Monika, Kanak, Jarosław, Ziętek, Sławomir, Stobiecki, Tomasz, Yao, Lide, Dijken, Sebastiaan van, Nozaki, Takayuki, Yakushiji, Kay, & Yuasa, Shinji. Temperature dependence of spin-orbit torques in W/CoFeB bilayers. United States. doi:10.1063/1.4960793.
Skowroński, Witold, E-mail: skowron@agh.edu.pl, Cecot, Monika, Kanak, Jarosław, Ziętek, Sławomir, Stobiecki, Tomasz, Yao, Lide, Dijken, Sebastiaan van, Nozaki, Takayuki, Yakushiji, Kay, and Yuasa, Shinji. 2016. "Temperature dependence of spin-orbit torques in W/CoFeB bilayers". United States. doi:10.1063/1.4960793.
@article{osti_22594311,
title = {Temperature dependence of spin-orbit torques in W/CoFeB bilayers},
author = {Skowroński, Witold, E-mail: skowron@agh.edu.pl and Cecot, Monika and Kanak, Jarosław and Ziętek, Sławomir and Stobiecki, Tomasz and Yao, Lide and Dijken, Sebastiaan van and Nozaki, Takayuki and Yakushiji, Kay and Yuasa, Shinji},
abstractNote = {We report on the temperature variation of spin-orbit torques in perpendicularly magnetized W/CoFeB bilayers. Harmonic Hall voltage measurements in perpendicularly magnetized CoFeB reveal increased longitudinal and transverse effective magnetic field components at low temperatures. The damping-like spin-orbit torque reaches an efficiency of 0.55 at 19 K. Scanning transmission electron microscopy and X-ray reflectivity measurements indicate that considerable interface mixing between W and CoFeB may be responsible for strong spin-orbit interactions.},
doi = {10.1063/1.4960793},
journal = {Applied Physics Letters},
number = 6,
volume = 109,
place = {United States},
year = 2016,
month = 8
}
  • We have studied the spin-orbit torques in perpendicularly magnetized Hf/CoFeB/MgO system, by systematically varying the thickness of Hf underlayer. We have observed a sign change of effective fields between Hf thicknesses of 1.75 and 2 nm, indicating that competing mechanisms, such as the Rashba and spin Hall effects, contribute to spin-orbit torques in our system. For larger Hf thicknesses (>2 nm), both the components of spin-orbit torques arise predominantly from the bulk spin Hall effect. We have also confirmed these results using spin-orbit torque induced magnetization switching measurements. Our results could be helpful in designing Hf based SOT devices.
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  • The spin orbital torques in Ta/CoFeB/MgO structures are experimentally investigated utilizing the planar Hall effect and magnetoresistance measurement. By angular field characterization of the planar Hall resistance at ±current, the differential resistance which is directly related to the spin orbital torques is derived. Upon curve fitting of the analytical formulas over the experimental results, it is found that the anti-damping torque, also known as spin Hall effect, is sizable while a negligible field-like torque is observed. A spin Hall angle of about 18 ± 0.6% is obtained for the Ta layer. Temperature dependent study of the spin orbital torques is also performed.more » It is found that temperature does not significantly modify the spin Hall angle. By cooling down the sample down to 100 K, the obtained spin Hall angle has a maximum value of about 20.5 ± 0.43%.« less
  • We study the effect of the oxide layer on current-induced perpendicular magnetization switching properties in Hf|CoFeB|MgO and Hf|CoFeB|TaO{sub x} tri-layers. The studied structures exhibit broken in-plane inversion symmetry due to a wedged CoFeB layer, resulting in a field-like spin-orbit torque (SOT), which can be quantified by a perpendicular (out-of-plane) effective magnetic field. A clear difference in the magnitude of this effective magnetic field (H{sub z}{sup FL}) was observed between these two structures. In particular, while the current-driven deterministic perpendicular magnetic switching was observed at zero magnetic bias field in Hf|CoFeB|MgO, an external magnetic field is necessary to switch the CoFeBmore » layer deterministically in Hf|CoFeB|TaO{sub x}. Based on the experimental results, the SOT magnitude (H{sub z}{sup FL} per current density) in Hf|CoFeB|MgO (−14.12 Oe/10{sup 7} A cm{sup −2}) was found to be almost 13× larger than that in Hf|CoFeB|TaO{sub x} (−1.05 Oe/10{sup 7} A cm{sup −2}). The CoFeB thickness dependence of the magnetic switching behavior, and the resulting  H{sub z}{sup FL} generated by in-plane currents are also investigated in this work.« less