Investigation of extrinsic damping caused by magnetic dead layer in Ta-CoFeB-MgO multilayers with perpendicular anisotropy

We systematically investigated the influence of the dead layer, the oxidation degree of naturally oxidized MgO, the structure of adjacent nonmagnetic metal layers on the damping parameter, and the perpendicular anisotropy of Ta(Ru)/Co20Fe60B20/MgO and MgO/Co20Fe60B20/Ta films using the vector networ...

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Bibliographic Details
Published in:Journal of applied physics 2016-03, Vol.119 (9)
Main Authors: Sato, Noriyuki, O'Brien, Kevin P., Millard, Kent, Doyle, Brian, Oguz, Kaan
Format: Article
Language:English
Subjects:
Anisotropy
Applied physics
Damping
Ferromagnetic materials
Ferromagnetic resonance
Magnesium oxide
Measurement techniques
Multilayers
Network analysers
Oxidation
Parameters
Tantalum
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Summary:We systematically investigated the influence of the dead layer, the oxidation degree of naturally oxidized MgO, the structure of adjacent nonmagnetic metal layers on the damping parameter, and the perpendicular anisotropy of Ta(Ru)/Co20Fe60B20/MgO and MgO/Co20Fe60B20/Ta films using the vector network analyzer ferromagnetic resonance measurement technique. MgO/Co20Fe60B20/Ta film shows almost twice larger extrinsic damping than that for Ta/Co20Fe60B20/MgO film, whereas the perpendicular anisotropy is much smaller. This two-fold enhancement of damping parameter is successfully explained by the extrinsic damping arises from the dead layer at the CoFeB-Ta interface through the Elliott-Yafet mechanism in addition to the conventional spin-pumping model. Furthermore, we found that the oxidation degree of naturally oxidized MgO has no significant impact on the damping parameter, while the perpendicular anisotropy for MgO/Co20Fe60B20/Ta film is enhanced by longer oxidation time.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4941943