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arXiv · 1210.8118

Mode- and size-dependent Landau-Lifshitz damping in magnetic nanostructures: Evidence for non-local damping

Hans T. Nembach·Justin M. Shaw·Carl T. Boone·T. J. Silva
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Abstract

We demonstrate a strong dependence of the effective damping on the nanomagnet size and the particular spin-wave mode that can be explained by the theory of intralayer transverse-spin-pumping. The effective Landau-Lifshitz damping is measured optically in individual, isolated nanomagnets as small as 100 nm. The measurements are accomplished by use of a novel heterodyne magneto-optical microwave microscope with unprecedented sensitivity. Experimental data reveal multiple standing spin-wave modes that we identify by use of micromagnetic modeling as having either localized or delocalized character, described generically as end- and center-modes. The damping parameter of the two modes depends on both the size of the nanomagnet as well as the particular spin-wave mode that is excited, with values that are enhanced by as much as 40% relative to that measured for an extended film. Contrary to expectations based on the ad hoc consideration of lithography-induced edge damage, the damping for the end-mode decreases as the size of the nanomagnet decreases. The data agree with the theory for damping caused by the flow of intralayer transverse spin-currents driven by the magnetization curvature. These results have serious implications for the performance of nanoscale spintronic devices such as spin-torque-transfer magnetic random access memory.

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Hans T. Nembach, Justin M. Shaw, Carl T. Boone, T. J. Silva. 2013-03-14. Mode- and size-dependent Landau-Lifshitz damping in magnetic nanostructures: Evidence for non-local damping. https://doi.org/10.1103/physrevlett.110.117201

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