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Evolution of damping in ferromagnetic/nonmagnetic thin film bilayers as a function of nonmagnetic layer thickness.

Azzawi, S. and Ganguly, A. and Tokaç, M. and Rowan-Robinson, R.M. and Sinha, J. and Hindmarch, A.T. and Barman, A. and Atkinson, D. (2016) 'Evolution of damping in ferromagnetic/nonmagnetic thin film bilayers as a function of nonmagnetic layer thickness.', Physical review B., 93 (5). 054402.

Abstract

The evolution of damping in Co/Pt, Co/Au, and Ni81Fe19/Pt bilayers was studied with increasing nonmagnetic (NM) heavy-metal layer thicknesses in the range 0.2nm≤tNM≤10nm, where tNM is the NM layer thickness. Magnetization precession was measured in the time domain using time-resolved magneto-optical Kerr effect magnetometry. Fitting of the data with a damped sinusoidal function was undertaken in order to extract the phenomenological Gilbert damping coefficient α. For Pt-capped Co and Ni81Fe19 layers a large and complex dependence of α on the Pt layer thickness was observed, while for Au capping no significant dependence was observed. It is suggested that this difference is related to the different localized spin-orbit interaction related to intermixing and to d−d hybridization of Pt and Au at the interface with Co or Ni81Fe19. Also it was shown that damping is affected by the crystal structure differences in FM thin films and at the interface, which can modify the spin-diffusion length and the effective spin-mixing conductance. In addition to the intrinsic damping an extrinsic contribution plays an important role in the enhancement of damping when the Pt capping layer is discontinuous. The dependence of damping on the nonmagnetic layer thickness is complex but shows qualitative agreement with recent theoretical predictions.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1103/PhysRevB.93.054402
Publisher statement:Reprinted with permission from the American Physical Society: Azzawi, S. and Ganguly, A. and Tokaç, M. and Rowan-Robinson, R.M. and Sinha, J. and Hindmarch, A.T. and Barman, A. and Atkinson, D. (2016) 'Evolution of damping in ferromagnetic/nonmagnetic thin film bilayers as a function of nonmagnetic layer thickness.', Physical review B., 93 (5). 054402 © 2016 by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modified, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.
Date accepted:17 December 2015
Date deposited:19 February 2016
Date of first online publication:01 February 2016
Date first made open access:19 February 2016

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