Magnetization dynamics and its scattering mechanism in thin CoFeB films with interfacial anisotropy

Atsushi Okada, Shikun He, Bo Gu, Shun Kanai, Anjan Soumyanarayanan, Sze Ter Lim, Michael Tran, Michiyasu Mori, Sadamichi Maekawa, Fumihiro Matsukura, Hideo Ohno, Christos Panagopoulos

Research output: Contribution to journalArticlepeer-review

39 Citations (Scopus)


Studies of magnetization dynamics have incessantly facilitated the discovery of fundamentally novel physical phenomena, making steady headway in the development of magnetic and spintronics devices. The dynamics can be induced and detected electrically, offering new functionalities in advanced electronics at the nanoscale. However, its scattering mechanism is still disputed. Understanding the mechanism in thin films is especially important, because most spintronics devices are made from stacks of multi-layers with nanometer thickness. The stacks are known to possess interfacial magnetic anisotropy, a central property for applications, whose influence on the dynamics remains unknown. Here, we investigate the impact of interfacial anisotropy by adopting CoFeB/ MgO as a model system. Through systematic and complementary measurements of ferromagnetic resonance (FMR) on a series of thin films, we identify narrower FMR linewidths at higher temperatures. We explicitly rule out the temperature dependence of intrinsic damping as a possible cause, and it is also not expected from existing extrinsic scattering mechanisms for ferromagnets. We ascribe this observation to motional narrowing, an old concept so far neglected in the analyses of FMR spectra. The effect is confirmed to originate from interfacial anisotropy, impacting the practical technology of spin-based nanodevices up to room temperature.

Original languageEnglish
Pages (from-to)3815-3820
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number15
Publication statusPublished - 2017 Apr 11


  • CoFeB/MgO
  • Damping
  • Ferromagnetic resonance
  • Interfacial anisotropy
  • Motional narrowing

ASJC Scopus subject areas

  • General


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