The dependence of the spin-pumping effect on the yttrium iron garnet (Y3Fe5O12, YIG) thickness detected by the inverse spin Hall effect (ISHE) has been investigated quantitatively. Due to the spin-pumping effect driven by the magnetization precession
in the ferrimagnetic insulator YIG film a spin-polarized electron current is injected into the Pt layer. This spin current is transformed into electrical charge current by means of the ISHE. An increase of the ISHE-voltage with increasing film thickness is observed and compared to the theoretically expected behavior. The effective damping parameter of the YIG/Pt samples is found to be enhanced with decreasing YIG film thickness. The investigated samples exhibit a spin mixing conductance of g=(7.43 pm 0.36) times 10^{18} m^{-2} and a spin Hall angle of theta_{ISHE} = 0.009 pm 0.0008. Furthermore, the influence of nonlinear effects on the generated voltage and on the Gilbert damping parameter at high excitation powers are revealed. It is shown that for small YIG film thicknesses a broadening of the linewidth due to nonlinear effects at high excitation powers is suppressed because of a lack of nonlinear multi-magnon scattering channels. We have found that the variation of the spin-pumping efficiency for thick YIG samples exhibiting pronounced nonlinear effects is much smaller than the nonlinear enhancement of the damping.
Conversion of traveling magnons into an electron carried spin current is demonstrated in a time resolved experiment using a spatially separated inductive spin-wave source and an inverse spin Hall effect (ISHE) detector. A short spin-wave packet is ex
cited in a yttrium-iron garnet (YIG) waveguide by a microwave signal and is detected at a distance of 3 mm by an attached Pt layer as a delayed ISHE voltage pulse. The delay in the detection appears due to the finite spin-wave group velocity and proves the magnon spin transport. The experiment suggests utilization of spin waves for the information transfer over macroscopic distances in spintronic devices and circuits.
Transmission of microwave spin waves through a microstructured magnonic crystal in the form of a permalloy waveguide of a periodically varying width was studied experimentally and theoretically. The spin wave characteristics were measured by spatiall
y-resolved Brillouin light scattering microscopy. A rejection frequency band was clearly observed. The band gap frequency was controlled by the applied magnetic field. The measured spin-wave intensity as a function of frequency and propagation distance is in good agreement with a model calculation.
The operational characteristics of a magnonic crystal, which was fabricated as an array of shallow grooves etched on a surface of a magnetic film, were compared for magnetostatic surface spin waves and backward volume magnetostatic spin waves. In bot
h cases the formation of rejection frequency bands was studied as a function of the grooves depth. It has been found that the rejection of the volume wave is considerably larger than of the surface one. The influences of the nonreciprocity of the surface spin waves as well as of the scattering of the lowest volume spin-wave mode into higher thickness volume modes on the rejection efficiency are discussed.
One-dimensional magnonic crystals have been implemented as gratings of shallow grooves chemically etched into the surface of yttrium-iron garnet films. Scattering of backward volume magnetostatic spin waves from such structures is investigated experi
mentally and theoretically. Well-defined rejection frequency bands are observed in transmission characteristics of the magnonic crystals. The loss inserted by the gratings and the rejections bands bandwidths are studied as a function of the film thickness, the groove depth, the number of grooves, and the groove width. The experimental data are well described by a theoretical model based on the analogy of a spin-wave film-waveguide with a microwave transmission line. Our study shows that magnonic crystals with required operational characteristics can be engineered by adjusting these geometrical parameters.
