Low Gilbert Damping Constant in Perpendicularly Magnetized W/CoFeB/MgO Films with High Thermal Stability

Dustin M. Lattery, Delin Zhang, Jie Zhu, Xudong Hang, Jian Ping Wang, Xiaojia Wang

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Perpendicular magnetic materials with low damping constant and high thermal stability have great potential for realizing high-density, non-volatile, and low-power consumption spintronic devices, which can sustain operation reliability for high processing temperatures. In this work, we study the Gilbert damping constant (α) of perpendicularly magnetized W/CoFeB/MgO films with a high perpendicular magnetic anisotropy (PMA) and superb thermal stability. The α of these PMA films annealed at different temperatures (Tann) is determined via an all-optical Time-Resolved Magneto-Optical Kerr Effect method. We find that α of these W/CoFeB/MgO PMA films decreases with increasing Tann, reaches a minimum of α = 0.015 at Tann= 350 °C, and then increases to 0.020 after post-annealing at 400 °C. The minimum α observed at 350 °C is rationalized by two competing effects as Tannbecomes higher: the enhanced crystallization of CoFeB and dead-layer growth occurring at the two interfaces of the CoFeB layer. We further demonstrate that α of the 400 °C-annealed W/CoFeB/MgO film is comparable to that of a reference Ta/CoFeB/MgO PMA film annealed at 300 °C, justifying the enhanced thermal stability of the W-seeded CoFeB films.

Original languageEnglish (US)
Article number13395
JournalScientific reports
Issue number1
StatePublished - Dec 1 2018

Bibliographical note

Funding Information:
This work is supported by C-SPIN (award #: 2013-MA-2381), one of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA. X.H. thanks Niron Magnetics, Inc. for financial support. The sample structural characterizations (XRD and XRR) were performed at the University of Minnesota Characterization Facility (CharFac), which received capital equipment funding from the University of Minnesota MRSEC under NSF Award DMR-1420013. The authors would like to thank Prof. Paul Crowell and Dr. Changjiang Liu for valuable discussions.

Publisher Copyright:
© 2018, The Author(s).

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