Coherent Spin Pumping in a Strongly Coupled Magnon-Magnon Hybrid System
Yi Li, Wei Cao, Vivek Amin, Zhizhi Zhang, Jonathan Gibbons, Joseph Sklenar, John E. Pearson, Paul M. Haney, M. D. Stiles, W. E. Bailey, V. Novosad, Axel Hoffmann, Wei Zhang
Abstract
We experimentally identify coherent spin pumping in the magnon-magnon hybrid modes of yttrium iron garnet/permalloy (YIG/Py) bilayers. By reducing the YIG and Py thicknesses, the strong interfacial exchange coupling leads to large avoided crossings between the uniform mode of Py and the spin wave modes of YIG enabling accurate determination of modification of the linewidths due to the dampinglike torque. We identify additional linewidth suppression and enhancement for the in-phase and out-of-phase hybrid modes, respectively, which can be interpreted as concerted dampinglike torque from spin pumping. Furthermore, varying the Py thickness shows that both the fieldlike and dampinglike couplings vary like 1/sqrt[t_{Py}], verifying the prediction by the coupled Landau-Lifshitz equations.