Direct Observation of Worm‐Like Nanochannels and Emergent Magnon Motifs in Artificial Ferromagnetic Quasicrystals

Abstract

Quasicrystalline structures and aperiodic metamaterials find applications ranging from established consumer gadgets to potential high‐tech photonic components owing to both complex arrangements of constituents and exotic rotational symmetries. Magnonics is an evolving branch of magnetism research where information is transported via magnetization oscillations (magnons). Their control and manipulation are so far best accomplished in periodic metamaterials which exhibit properties artificially modulated on the nanoscale. They give rise to functional components, such as band stop filters, magnonic transistors and nanograting couplers. Here, spin‐wave excitations in artificial ferromagnetic quasicrystals created via aperiodic arrangement of nanoholes are studied experimentally. Their ten‐fold rotational symmetry results in multiplexed magnonic nanochannels, suggesting a width down to 50 nm inside a so‐called Conway worm. Key elements of design are emergent magnon motifs and the worm‐like features which are scale‐invariant and not present in the periodic metamaterials. By imaging wavefronts in quasicrystals, insight is gained into how the discovered features materialize as a dense wavelength division multiplexer.

Direct observation of multiband transport in magnonic Penrose quasicrystals via broadband and phase-resolved spectroscopy

“…The nanochannel formation is due to the inhomogeneous internal field, which takes locally small values because of the demagnetization effect of the nanotroughs, and resonant spin precession occurs at correspondingly small excitation frequency. The nanochannels in P3-MQC appear to be irregular, consistent with ( 12 ). In the following, we present broadband SW spectroscopy based on a vector network analyzer (VNA) to explore the frequency dependence of SW absorption and transmission in P3-MQC in detail and compare the results with SQ-MC and a plane film.…”

“…These gaps and SW propagation in 1D quasicrystals were evidenced using Brillouin light scattering (BLS) and x-ray microscopy techniques ( 14 , 15 ). Furthermore, worm-like nanochannels found in 2D antidot quasicrystals gave rise to an unprecedented demultiplexing process with microwaves that showed distinct advantages over demultiplexing process in photonics ( 12 ). In addition, the reprogrammability of artificial quasicrystals ( 10 , 14 , 16 ) promised a data writing process.…”

Resonant dynamics of skyrmion lattices in thin film multilayers: Localised modes and spin wave emission

“…However the properties of the skyrmion lattice as a magnonic crystal also needs to be explored using broadband propagating SW spectroscopy 10 or advanced SW imaging methods 9,25 . Lastly, our system could serve as a platform to study magnon-skyrmion scattering 39 , emergent magnon motifs 59 , or chiral magnonic edge states 60 .…”

Advances in Magnetics Roadmap on Spin-Wave Computing

“…During the last decade, research on fundamental aspects and functional properties of spin waves on the nanoscale has significantly grown. Nanotechnology applied to both ferromagnetic metals and the ferrimagnetic insulator YIG enables lateral sizes of spin-wave channels down to sub-100 nm length scale in planar (2D) magnonic crystals [211] and individual magnon waveguides [39]. Microwave-to-magnon transducers based on coplanar waveguides (CPWs) have shown emission and detection of magnons in YIG with wavelengths l down to 50 nm [28] and promise even shorter l [50], [29].…”