Stacking order-dependent sign-change of microwave phase due to eddy currents in nanometer-scale NiFe/Cu heterostructures

Type
Preprint

Authors
Gladii, O.
Seeger, R. L.
Frangou, L.
Forestier, G.
Ebels, U.
Auffret, S.
Baltz, V.

KAUST Grant Number
Grant No. OSR-2015-CRG4-2626

Preprint Posting Date
2019-02-18

Online Publication Date
2019-07-18

Print Publication Date
2019-07-15

Date
2019-07-18

Abstract
In the field of spintronics, ferromagnetic/non-magnetic metallic multilayers are core building blocks for emerging technologies. Resonance experiments using stripline transducers are commonly used to characterize and engineer these stacks for applications. Up to now in these experiments, the influence of eddy currents on the excitation of the dynamics of ferromagnetic magnetization below the skin-depth limit was most often neglected. Here, using a coplanar stripline transducer, we experimentally investigated the broadband ferromagnetic resonance response of NiFe/Cu bilayers a few nanometers thick in the sub-skin-depth regime. Asymmetry in the absorption spectrum gradually built up as the excitation frequency and Cu-layer thickness increased. Most significantly, the sign of the asymmetry depended on the stacking order. Experimental data were consistent with a quantitative analysis considering eddy currents generated in the Cu layers and the subsequent phaseshift of the feedback magnetic field generated by the eddy currents. These results extend our understanding of the impact of eddy currents below the microwave magnetic skin-depth and explain the lineshape asymmetry and phase lags reported in stripline experiments.

Citation
Appl. Phys. Lett. 115, 032403 (2019)

Acknowledgements
We acknowledge financial support from the French national research agency (ANR) (Grant No. ANR-15-CE24-0015-01) and KAUST (Grant No. OSR-2015-CRG4-2626). We also thank M. Gallagher-Gambarelli for the critical reading of the manuscript.

Publisher
AIP Publishing

DOI
10.1063/1.5093150

arXiv
1902.06501

Additional Links
https://arxiv.org/pdf/1902.06501http://arxiv.org/pdf/1902.06501

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