TY - JOUR
T1 - Spin-Torque Ferromagnetic Resonance in W/Co - Fe - B/ W/Co - Fe - B/Mg O Stacks
AU - He, Congli
AU - Yu, Guoqiang
AU - Grezes, Cecile
AU - Feng, Jiafeng
AU - Zhao, Zhen
AU - Razavi, Seyed Armin
AU - Shao, Qiming
AU - Navabi, Aryan
AU - Li, Xiang
AU - He, Qing Lin
AU - Li, Mengyin
AU - Zhang, Jia
AU - Wong, Kin L.
AU - Wei, Dan
AU - Zhang, Guangyu
AU - Han, Xiufeng
AU - Khalili, Pedram
AU - Wang, Kang L.
N1 - Funding Information:
This work was supported by financial support from the National Natural Science Foundation of China (NSFC, Grant No.11874409), National Natural Science Foundation of China (NSFC)-Science Foundation Ireland (SFI) Partnership Programme (Grant No. 51861135104), and 1000 Youth Talents Program. This work was also supported in part by C-SPIN and FAME, two of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA. This work was also supported by the National Science Foundation (Grant No. ECCS 1611570) and Nanosystems Engineering Research Center for Translational Applications of Nanoscale Multiferroic Systems (TANMS) Cooperative Agreement Award No. EEC-1160504.
Publisher Copyright:
© 2018 American Physical Society.
PY - 2018/9/28
Y1 - 2018/9/28
N2 - We investigate the magnetic properties of as-grown and annealed W/Co-Fe-B/W(insertion)/Co-Fe-B/MgO stacks with different thicknesses of Co-Fe-B layers and W insertion layers using spin-torque ferromagnetic resonance (ST FMR) technique. The dependences of perpendicular magnetic anisotropy (PMA), damping constant, and interlayer exchange coupling on the annealing, Co-Fe-B layer thicknesses, and W insertion layer thicknesses are systematically studied. The PMA is strongly enhanced after annealing at 400 °C. Nevertheless, the Gilbert damping constant remains nearly unchanged after annealing. The PMA also increases with the thickness of the W insertion layer. Both acoustic (in-phase) mode and optical (out-of-phase) mode are observed. The optical mode, which is typically weak when using the conventional FMR measurement, shows a comparable magnitude to the acoustic mode. The effective excitation of the optical mode is ascribed to the nonuniform spin-orbit torque acting on the two coupled layers. Furthermore, the interlayer exchange coupling (ferromagnetic or antiferromagnetic) can be identified through analyzing the two resonance modes, which is found to depend on the W insertion layer thickness, Co-Fe-B layer thickness, and annealing conditions. The experimental results will be useful for developing high-frequency magnetic devices based on magnetic multilayer films with high PMA and thermal stability. Our experimental results also show that the ST FMR is an effective methodology for studying interlayer exchange coupled systems.
AB - We investigate the magnetic properties of as-grown and annealed W/Co-Fe-B/W(insertion)/Co-Fe-B/MgO stacks with different thicknesses of Co-Fe-B layers and W insertion layers using spin-torque ferromagnetic resonance (ST FMR) technique. The dependences of perpendicular magnetic anisotropy (PMA), damping constant, and interlayer exchange coupling on the annealing, Co-Fe-B layer thicknesses, and W insertion layer thicknesses are systematically studied. The PMA is strongly enhanced after annealing at 400 °C. Nevertheless, the Gilbert damping constant remains nearly unchanged after annealing. The PMA also increases with the thickness of the W insertion layer. Both acoustic (in-phase) mode and optical (out-of-phase) mode are observed. The optical mode, which is typically weak when using the conventional FMR measurement, shows a comparable magnitude to the acoustic mode. The effective excitation of the optical mode is ascribed to the nonuniform spin-orbit torque acting on the two coupled layers. Furthermore, the interlayer exchange coupling (ferromagnetic or antiferromagnetic) can be identified through analyzing the two resonance modes, which is found to depend on the W insertion layer thickness, Co-Fe-B layer thickness, and annealing conditions. The experimental results will be useful for developing high-frequency magnetic devices based on magnetic multilayer films with high PMA and thermal stability. Our experimental results also show that the ST FMR is an effective methodology for studying interlayer exchange coupled systems.
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U2 - 10.1103/PhysRevApplied.10.034067
DO - 10.1103/PhysRevApplied.10.034067
M3 - Article
AN - SCOPUS:85054578212
VL - 10
JO - Physical Review Applied
JF - Physical Review Applied
SN - 2331-7019
IS - 3
M1 - 034067
ER -