Stacking order-dependent sign-change of microwave phase due to eddy currents in nanometer-scale NiFe/Cu heterostructures
KAUST Grant NumberGrant No. OSR-2015-CRG4-2626
Preprint Posting Date2019-02-18
Online Publication Date2019-07-18
Print Publication Date2019-07-15
Permanent link to this recordhttp://hdl.handle.net/10754/660852
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AbstractIn 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.
CitationAppl. Phys. Lett. 115, 032403 (2019)
SponsorsWe 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.