Long-range spin-wave propagation in transversely magnetized nano-scaled conduits

Abstract

Magnonics attracts increasing attention in the view of low-energy computation technologies based on spin waves. Recently, spin-wave propagation in longitudinally magnetized nano-scaled spin-wave conduits was demonstrated, proving the fundamental feasibility of magnonics at the sub-100 nm scale. Transversely magnetized nano-conduits, which are of great interest in this regard as they offer a large group velocity and a potentially chirality-based protected transport of energy, have not yet been investigated due to their complex internal magnetic field distribution. Here, we present a study of propagating spin waves in a transversely magnetized nanoscopic yttrium iron garnet conduit of 50 nm width. Space and time-resolved microfocused Brillouin-light-scattering spectroscopy is employed to measure the spin-wave group velocity and decay length. A long-range spin-wave propagation is observed with a decay length of up to (8.0 ± 1.5) μm and a large spin-wave lifetime of up to (44.7 ± 9.1) ns. The results are supported with micromagnetic simulations, revealing a broad single-mode frequency range and the absence of a mode localized to the edges. Furthermore, a frequency nonreciprocity for counter-propagating spin waves is observed in the simulations and the experiment, caused by the trapezoidal cross section of the structure. The revealed long-distance spin-wave propagation on the nano-scale is particularly interesting for an application in spin-wave devices, allowing for long-distance transport of information in magnonic circuits and low-energy device architectures.

Advances in Magnetics Roadmap on Spin-Wave Computing

“…Their magnetostatic and dynamic behavior is similar to single crystal bulk YIG, and the Gilbert damping coefficient α || is independent of the film thickness and is close to 1 × 10 −4 [42]. The perfection of nm-thin YIG LPE films has already enabled the fabrication of 50 nm wide nano-scaled conduits with spin-wave propagation decay lengths of 8 micrometer [46]. Furthermore, control of intermodal dissipation processes of strongly driven propagating spin waves in nanodevices has been achieved [47] and the first magnon-based data processing devices such as magnonic directional couplers have been realized [48], with all of these devices operating in a singlemode regime.…”

“…This large frequency gap is sufficient for single-mode spin-wave operation. In such a waveguide, propagating spin waves have been measured using micro-focused Brillouin light scattering spectroscopy in both longitudinally and transversally magnetized configurations [39], [46]. A long-range spin-wave propagation has been observed in transversely magnetized waveguides, with a decay length of up to 8 µm and a large spinwave lifetime of up to 48 ns [46].…”

“…In such a waveguide, propagating spin waves have been measured using micro-focused Brillouin light scattering spectroscopy in both longitudinally and transversally magnetized configurations [39], [46]. A long-range spin-wave propagation has been observed in transversely magnetized waveguides, with a decay length of up to 8 µm and a large spinwave lifetime of up to 48 ns [46]. Moreover, a frequency nonreciprocity for counter-propagating spin waves is found which is caused by the trapezoidal cross-section of the structure.…”

“…The comparatively large spinwave loss is a challenge which will limit the number of magnons reaching a detector region. Nevertheless, the recentlydeveloped 50 nm-wide single-mode spin-wave waveguides offer relatively large propagation lengths of about 10 µm [46] which should be sufficient for quantum operations at the nanoscale. Thus, besides a set of technical questions, the main challenges will involve the realization of efficient singlemagnon sources and detectors.…”

A modal approach to modelling spin wave scattering

“…In recent years, we have observed a rapid progress in the development of components for magnonic circuitry. Conduits for single and multimode spin-wave transfer [1][2][3][4][5], phase control [6][7][8][9], spin-wave valves [10], couplers [11,12], resonators [13][14][15], transducers, diodes [16], and logic gates [17,18] are only selected examples based on various physical principles. To understand the physics of the spin-wave phenomena behind the observed functionalities, increase the effectiveness of their operation and find their new realisations, researchers need suitable models and numerical methods.…”