Unidirectional spin-torque driven magnetization dynamics

Joseph Sklenar, Wei Zhang, Matthias B. Jungfleisch, Hilal Saglam, Scott Grudichak, Wanjun Jiang, John E. Pearson, John B. Ketterson, Axel Hoffmann

Research output: Contribution to journalArticlepeer-review


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 tipped 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.

Original languageEnglish (US)
Article number224431
JournalPhysical Review B
Issue number22
StatePublished - Jun 27 2017
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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