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Title: Unidirectional spin-torque driven magnetization dynamics

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Publication Date:
Sponsoring Org.:
OSTI Identifier:
Grant/Contract Number:
AC02-06CH11357; SC0014424
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 95; Journal Issue: 22; Related Information: CHORUS Timestamp: 2017-06-27 22:12:08; Journal ID: ISSN 2469-9950
American Physical Society
Country of Publication:
United States

Citation Formats

Sklenar, Joseph, Zhang, Wei, Jungfleisch, Matthias B., Saglam, Hilal, Grudichak, Scott, Jiang, Wanjun, Pearson, John E., Ketterson, John B., and Hoffmann, Axel. Unidirectional spin-torque driven magnetization dynamics. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.95.224431.
Sklenar, Joseph, Zhang, Wei, Jungfleisch, Matthias B., Saglam, Hilal, Grudichak, Scott, Jiang, Wanjun, Pearson, John E., Ketterson, John B., & Hoffmann, Axel. Unidirectional spin-torque driven magnetization dynamics. United States. doi:10.1103/PhysRevB.95.224431.
Sklenar, Joseph, Zhang, Wei, Jungfleisch, Matthias B., Saglam, Hilal, Grudichak, Scott, Jiang, Wanjun, Pearson, John E., Ketterson, John B., and Hoffmann, Axel. 2017. "Unidirectional spin-torque driven magnetization dynamics". United States. doi:10.1103/PhysRevB.95.224431.
title = {Unidirectional spin-torque driven magnetization dynamics},
author = {Sklenar, Joseph and Zhang, Wei and Jungfleisch, Matthias B. and Saglam, Hilal and Grudichak, Scott and Jiang, Wanjun and Pearson, John E. and Ketterson, John B. and Hoffmann, Axel},
abstractNote = {},
doi = {10.1103/PhysRevB.95.224431},
journal = {Physical Review B},
number = 22,
volume = 95,
place = {United States},
year = 2017,
month = 6

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on June 27, 2018
Publisher's Accepted Manuscript

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Cited by: 1work
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  • The rich physics associated with magnetism often centers around directional effects. Here we demonstrate how spin-transfer torques in general result in unidirectional ferromagnetic resonance dynamics upon field reversal. The unidirectionality is a direct consequence of both field-like and damping-like dynamic torques simultaneously driving the motion. This directional effect arises from the field-like torque being odd and the damping-like torque being even under field reversal. The directional effect is observed when the magnetization has both an in-plane and out-of-plane component, since then the linear combination of the torques rotates with a different handedness around the magnetization as the magnetization is tippedmore » out-of-plane. The effect is experimentally investigated via spin-torque ferromagnetic resonance measurements with the field applied at arbitrary directions away from the interface normal. The measured asymmetry of the voltage spectra are well explained within a phenomenological torque model.« less
  • We studied spin-transfer-torque (STT) switching of a cross-shaped magnetic tunnel junction in a recent report [Roy et al., J. Appl. Phys. 113, 223904 (2013)]. In that structure, the free layer is designed to have four stable energy states using the shape anisotropy of a cross. STT switching showed different regions with increasing current density. Here, we employ the micromagnetic spectral mapping technique in an attempt to understand how the asymmetry of cross dimensions and spin polarization direction of the injected current affect the magnetization dynamics. We compute spatially averaged frequency-domain spectrum of the time-domain magnetization dynamics in the presence ofmore » the current-induced STT term. At low currents, the asymmetry of polarization direction and that of the arms are observed to cause a splitting of the excited frequency modes. Higher harmonics are also observed, presumably due to spin-wave wells caused by the regions of spatially non-uniform effective magnetic field. The results could be used towards designing a multi-bit-per-cell STT-based random access memory with an improved storage density.« less
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  • Magnetization reversal of a magnetic free layer under spin transfer torque (STT) effect from a magnetic hard layer with a fixed magnetization direction and an oscillating layer is investigated. By including STT from the oscillating layer with in-plane anisotropy and orthogonal polarizer, magnetization-time dependence of free layer is determined. The results show that the frequency and amplitude of oscillations can be varied by adjusting the current density and magnetic properties. For an optimal oscillation frequency (f{sub opt}), a reduction of the switching time (t{sub 0}) of the free layer is observed. Both f{sub opt} and t{sub 0} increase with themore » anisotropy field of the free layer.« less
  • We demonstrate magnetization switching in out-of-plane magnetized Ta\CoFeB\MgO nanowires by current pulse injection along the nanowires, both with and without a constant and uniform magnetic field collinear to the current direction. We deduce that an effective torque arising from spin-orbit effects in the multilayer drives the switching mechanism. While the generation of a component of the magnetization along the current direction is crucial for the switching to occur, we observe that even without a longitudinal field thermally generated magnetization fluctuations can lead to switching. Analysis using a generalized Néel-Brown model enables key parameters of the thermally induced spin-orbit torques-driven switchingmore » process to be estimated, such as the attempt frequency and the effective energy barrier.« less