Magnetization dynamics and its scattering mechanism in thin CoFeB films with interfacial anisotropy.
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 multilayers 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.
Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan.
Atsushi
A
Okada
Divison of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore.|Data Storage Institute, Agency for Science, Technology and Research (A*STAR), 138634 Singapore.
Shikun
S
He
Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan.
Bo
B
Gu
Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan.|Center for Spintronics Integrated Systems, Tohoku University, Sendai 980-8577, Japan.|Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan.
Shun
S
Kanai
Divison of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore.|Data Storage Institute, Agency for Science, Technology and Research (A*STAR), 138634 Singapore.
Anjan
A
Soumyanarayanan
Data Storage Institute, Agency for Science, Technology and Research (A*STAR), 138634 Singapore.
Sze Ter
ST
Lim
Data Storage Institute, Agency for Science, Technology and Research (A*STAR), 138634 Singapore.
Michael
M
Tran
Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan.
Michiyasu
M
Mori
Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan.|Exploratory Research for Advanced Technology, Japan Science and Technology Agency, Sendai 980-8577, Japan.
Sadamichi
S
Maekawa
Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan; f-matsu@wpi-aimr.tohoku.ac.jp christos@ntu.edu.sg.|Center for Spintronics Integrated Systems, Tohoku University, Sendai 980-8577, Japan.|Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan.|World Premier International Research Center-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
Fumihiro
F
Matsukura
Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan.|Center for Spintronics Integrated Systems, Tohoku University, Sendai 980-8577, Japan.|Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan.|World Premier International Research Center-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.|Center for Innovative Integrated Electronic Systems, Tohoku University, Sendai 980-0845, Japan.
Hideo
H
Ohno
Divison of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore; f-matsu@wpi-aimr.tohoku.ac.jp christos@ntu.edu.sg.
Christos
C
Panagopoulos
CoFeB/MgO; damping; ferromagnetic resonance; interfacial anisotropy; motional narrowing