Artificial intelligence is driving intense interest in alternative computing hardware capable of neural information processing beyond conventional charge-based electronics. Among emerging approaches, wave-based computing promises highly parallel and energy-efficient operation, but scalable physical neural hardware has remained elusive because wave systems generally lack cascadable nonlinear neurons with signal regeneration and phase-robust operation. Here we demonstrate integrated magnonic neural circuits based on nonlinear threshold neurons realized in nanoscale yttrium iron garnet waveguides. The neurons perform weighted summation of multiple spin-wave inputs, while a pump-controlled nonlinear activation defines continuously tunable firing thresholds. Owing to deeply nonlinear spin-wave dynamics, the activated neurons emit self-normalized outputs whose intensities are largely independent of the input amplitudes, while nonlinear phase self-adjustment suppresses sensitivity to the relative input phases, enabling deterministic neuron-to-neuron cascading without external signal restoration. We experimentally realize programmable threshold neurons, reconfigurable weighted classification and deterministic cascading between sequential neuronal stages, and further demonstrate reconfigurable physical pattern recognition in a seven-neuron integrated magnonic circuit through experimental classification of the binary letter patterns 'HUST'. These results establish nonlinear magnons as a scalable platform for integrated neural hardware and position nonlinear wave dynamics as a general paradigm for physical neuromorphic computing.

Coupling light to magnetic excitations in the form of spin waves underpins both the optical study of magnetism and emerging schemes for quantum transduction, positioning the quanta of these excitations, magnons, as promising carriers for hybrid quantum networks. However, exploiting them in the quantum regime requires millikelvin temperatures to suppress thermal magnon populations, thereby confining such experiments to dilution refrigerators. There, magnons can already be excited and read out electrically, yet an optical interface required for microwave-to-optical photon conversion has been missing. Here, we demonstrate the first optical detection of coherently driven, propagating spin waves via Brillouin Light Scattering (BLS) spectroscopy inside a dilution refrigerator. By simultaneously recording the optical and electrical responses of the same spin-wave mode in a yttrium iron garnet film, we find that the BLS spectra track the electrically measured transmission across a range of applied magnetic fields. For the lowest optical power of 7.9 μW that still enabled spin-wave detection, we measured a global equilibrium sample temperature of 510 mK via a resistance thermometer, while numerical modelling of the laser-induced heating yields a maximum local temperature of 900 mK at the focal spot. This brings free-space optical access to magnons into the sub-kelvin regime, representing a milestone towards magnon-mediated quantum transduction in hybrid quantum systems.

True random number generators (TRNGs) underpin modern cryptography, yet existing implementations face fundamental trade-offs between speed, scalability, and entropy quality. Here, we demonstrate that stochastic switching in the bistable regime of spin-wave dynamics provides a physical entropy source for high-quality random number generation. Our magnonic random number generator (mRNG), based on a lithography-patterned microstrip on yttrium iron garnet (YIG), exploits thermal fluctuations near the nonlinear bistable regime to generate random bitstreams that pass all 15 NIST SP 800-22 statistical tests at rates with 20 Mb/s. We implement a random-bit multiplier using synchronized mRNG units and demonstrate scalability to 200-nm-wide nanoscale waveguides, establishing spin-wave bistability as a viable physical entropy source for integrated random number generation.

Nonlinear magnetization dynamics offers a rich variety of phenomena ranging from bistability to chaos. Here, we report the ultrafast formation of a dynamic magnetic soliton in thin ferrimagnetic garnet films with perpendicular magnetic anisotropy, driven by the microwave magnetic field of a microstrip antenna. Using time-resolved Brillouin light scattering microscopy and scanning transmission X-ray microscopy, we directly track the build-up of the large-angle precession state. The observed soliton is distinct from other nonlinear magnetic excitations in two key aspects: (i) it forms inside the linear spin-wave frequency band, and (ii) it is exceptionally large, reaching tens of microns beyond the antenna. We explain the soliton formation by the self-limiting mechanism upon a positive nonlinear frequency shift and the spatial extent of the near-field of the antenna. At large distances from the drive, the soliton collapses and emits short-wavelength spin waves via almost instantaneous spatial wavenumber conversion. Time-resolved measurements further reveal a small finite delay during soliton formation, while coherent long-range oscillations appear essentially simultaneously over distances up to 40 micrometers. These results establish microwave-driven solitons as a robust nonlinear phenomenon in thin-film garnets and suggest opportunities for fast, nonlocal manipulation of magnetic states and for applications in novel computational schemes.

Parametric pumping is a powerful tool for the excitation, amplification, and processing of oscillations and waves of different nature. In general, parametric resonance can occur when the pumping frequency f_p and eigenfrequency of a linear mode (or wave) f_0 satisfy the relation f_p=2f_0/n (n=1,2,3,...). While such parametric resonance is well known in mechanical, superconductive, and quantum systems, in magnetic and spintronic systems only the lowest (n=1) parametric resonance at double the spin wave mode frequency f_p=2f_0 was thoroughly studied and explored. Here, using a theoretical analysis based on both micromagnetic simulations and an analytical model, we show the emergence of resonances at fractional frequencies f_p=2f_0/n (with n>10) in spintronic diodes driven by the simultaneous action of ac spin-transfer torque (STT, current densities < 10^6 A/cm2) and voltage-controlled magnetic anisotropy (VCMA, effective anisotropy fields < 50 mT). The analytical model shows that parametric magnetization dynamics is irreducible to the standard Mathieu model of a parametric oscillator and demonstrates the crucial role of VCMA-driven mode frequency modulation: together with parametric coupling, it results in higher-order odd (n=3,5,7,...) fractional resonances, observed above certain VCMA pumping threshold, while simultaneous action with linear STT drive produces thresholdless even (n=4,6,8,...) resonances. This higher-order parametric dynamics is not restricted to VCMA pumping and opens new directions for the application of spintronic diodes for nonlinear signal processing and electromagnetic energy harvesting.

The transistor transformed not only electronics but everyday life, and the integrated circuit - now simply the "chip" - made computation scalable and ubiquitous. Magnonics has long promised a parallel path to low-energy information processing by using spin waves instead of charge. Progress, however, has been limited by two fundamental obstacles: intrinsic attenuation of spin waves and the requirement for precisely normalised output intensity and input phase to ensure reliable logic operation - conditions that are difficult to maintain in large-scale circuits owing to inevitable imperfections. Here, we report an integrated magnonic circuit that overcomes both limitations through engineered nonlinearity in nanoscale yttrium iron garnet waveguides. Nonlinear self-adjustment of the spin wave phase renders logic operation insensitive to the relative phases of the inputs, while a deeply nonlinear, threshold-activated self-normalised excitation restores and standardises the output intensity. Using space-resolved micro-focused Brillouin light scattering, we demonstrate reconfigurable AND, OR and three-input majority gates and realise deterministic cascading across sequential stages, establishing a scalable on-chip logic primitive. The architecture operates with gigahertz frequencies, supports dynamic threshold control for functional reconfiguration, and is compatible with scalable integration, making it attractive for adaptive and neuromorphic computing. By resolving phase-independent operation and signal restoration at the level of device physics, this work advances magnonics from isolated proof-of-concept devices towards integrated magnonic chips that can complement advanced CMOS in energy-constrained computing tasks.

ABSTRACT Wave‐based platforms for unconventional computing require a controlled yet adjustable flow of wave information, integrated with non‐volatile data storage. Spin waves are ideal for such platforms due to their inherent nonreciprocal properties and direct interaction with magnetic storage. This study demonstrates how spin‐wave nonreciprocity, induced by dipolar interactions in nanowaveguides with antiparallel out‐of‐plane magnetization, enables the realization of a spin‐wave circulator for unidirectional signal transport and advanced routing. The device's functionality can be continuously reconfigured using a magnetic domain wall with adjustable position, offering non‐volatile control over output and nonreciprocity. These features are illustrated using a spin‐wave directional coupler, validated through micromagnetic simulations and analytical models, which also support the functions of a waveguide crossing, tunable power splitter, and frequency multiplexer. The proposed domain‐wall‐based reconfiguration, combined with nonlinear spin‐wave behavior, holds promise for developing a nanoscale, nonlinear wave computing platform with self‐learning capabilities.

Magnons have inspired potential applications in modern quantum technologies and hybrid quantum systems due to their intrinsic nonlinearity, nanoscale scalability, and a unique set of experimentally accessible parameters for manipulating their dispersion. Such magnon-based quantum technologies demand long decoherence times, millikelvin temperatures, and minimal dissipation. Due to its low magnetic damping, the ferrimagnet yttrium iron garnet (YIG), grown on gadolinium gallium garnet (GGG), is the most promising material for this objective. To comprehend the magnetic losses of propagating magnons in such YIG-GGG heterostructures at cryogenic temperatures, we investigate magnon transport in a micrometer-thick YIG sample via propagating spin-wave spectroscopy measurements for temperatures between 4 K to 26 mK. We demonstrate an increase in the dissipation rate with wavenumber at cryogenic temperatures, caused by dipolar coupling to the partially magnetized GGG substrate. Additionally, we observe a temperature-dependent decrease in spin-wave transmission, attributed to rare earth ion relaxations. The critical role of the additional dissipation channels at cryogenic temperatures is underpinned by the comparison of the experimental results with theoretical calculations and micromagnetic simulations. Our findings strengthen the understanding of magnon losses at millikelvin temperatures, which is essential for the future detection of individual propagating magnons.

Magnonics offers nanometer-scale wave propagation and strong nonlinearities, making it attractive for neuromorphic applications such as artificial neurons. Yet, magnonic elements with interconnections solely within the magnonic system remain challenging, preventing the realization of interconnected magnonic neurons to date. Here, we experimentally demonstrate an all-magnonic neuron that reacts to magnon inputs with thresholded, amplified magnon firing and subsequent self-reset, enabling all-magnonic operation and cascading. Our approach is based on micro-antenna excitation on an ultra-low damping garnet with perpendicular magnetic anisotropy (PMA), where we exploit the positive magnon frequency shift to realize nonlinear activation. Using Brillouin light scattering spectroscopy, we uncover a transient neuron response with tunable fading memory: A 25

The manipulation of magnetization lies at the heart of spintronic and magnonic technologies, with the ultimate performance of such systems limited by the velocity at which magnetic excitations can propagate. Here, we demonstrate ultrafast propagation of magnon-polaritons-hybrid quasiparticles arising from the coupling between spin waves and electromagnetic fields in thin pure, bismuth-, and gallium substituted yttrium iron garnet (YIG, Bi:YIG and Ga:YIG) films. Using time- and phase-resolved Brillouin light scattering microscopy and time-resolved scanning transmission microscopy, we show that magnon-polaritons can propagate faster than 100 km/s, nearly three orders of magnitude more than conventional spin waves, and can be observed at distances exceeding 40 micrometers in 20 nm thick films. Analytical modeling based on retarded Maxwell equations and Polder tensor formalism confirms the hybridized nature of the excitations and captures the nontrivial dispersion and attenuation profiles. Notably, the magnon-polaritons maintain high initial magnetization amplitudes and long decay lengths, enabling ultrafast manipulation of the magnetization far away from the excitation source. We show, that they can move domain walls or stabilize nonlinear magnetization processes. The unprecedentedly high propagation velocities make magnon-polaritons promising candidates for high-speed information transfer in future spin-based computing architectures, potentially overcoming long-standing group delay bottlenecks in magnonic logic circuits.

Three-wave scattering is a fascinating phenomenon with many applications in various technologies. Reducing the system symmetry greatly affects three-wave scattering, which, in this case, goes beyond the simple momentum conservation law. In this study, we examine three-magnon scattering at the edge of a thin ferromagnetic film, when a bulk spin wave interacts with an edge-localized propagating spin wave upon the reflection. This creates new bulk spin waves at mixed frequencies by means of three-magnon confluence or stimulated splitting processes. Using our developed analytical theory, which has been confirmed by full micromagnetic simulations, we demonstrate that the amplitude of the wave generated in the stimulated splitting process is several times larger than that generated in the confluence process. This is primarily due to the lower group velocity of the wave formed in the splitting process than in confluence. Furthermore, the intensity of inelastically scattered waves exhibits a pronounced dependence on the incidence angle and frequency of the edge spin wave that goes beyond existing qualitative models. We show that the observed behaviors can only be explained by taking into account that the scattered waves are created by several elementary three-magnon processes involving the incident and reflected waves. The complex nature of the scattered wave creation results in a strong sensitivity of its amplitude to the phase accumulation of spin waves upon reflection.

Dipolar coupling between closely spaced magnetic waveguides enables magnonic directional couplers serving as signal combiners, power splitters, demultiplexers, and more. The wavelength-dependent coupling, combined with the weak nonlinear variation of spin-wave wavelength at constant frequency, introduces power-dependent characteristics of directional couplers. This property has been utilized in magnonic logic elements and other applications. Here, we explore a different nonlinear phenomenon in a directional coupler arising purely from the spin-wave nonlinear frequency shift. A strong nonlinear frequency shift causes the coupler to behave as if composed of nonidentical waveguides, suppressing energy transfer between the waveguides. The transition from complete to negligible energy transfer exhibits a sharp threshold behavior, with the critical power determined by the coupling strength and nonlinear frequency shift parameter. Based on these findings, a switchable directional coupler with potential to operate at higher frequencies of exchange-dominated spin waves for magnonic circuits is designed and validated by micromagnetic simulations.

Materials are commonly distinguished by their magnetic response into diamagnetic, paramagnetic, and magnetically ordered (ferro-, ferri-, and antiferromagnetic) phases. Diamagnets and paramagnets lack spontaneous long-range order, whereas ordered magnets develop such order below their Curie or Néel temperature and support single spin-wave excitations (magnons). Magnons have found applications in radio-frequency technologies and computation, magneto-optics, and foundational quantum experiments. Above the Curie/Néel temperature, long-range order is lost and the material transitions to a paramagnetic phase, with localised spin alignment in small patches, producing paramagnons with only short-range propagation. Here we show that long-range coherence is preserved in the organic free radical 2,2,6,6-tetramethylpiperidin-1-oxyl above the Néel temperature using all-electrical propagating spin-wave spectroscopy in external magnetic fields. We observe coherently excited low-energy paramagnon-polaritons up to 23 𝐆𝐇𝐳 , propagating over 8 𝐦𝐦 at supersonic group velocities exceeding 100 𝐤𝐦 𝐬^-1. Using free radicals as magnon carriers integrates organic materials with spintronics and opens the way to organic electronics, dense information storage, and quantum technologies.

Spin-wave-based computing has emerged as a promising approach to overcome the fundamental limitations of CMOS technologies. However, the increasing demand for device miniaturization down to a 100 nm scale presents significant challenges for long-distance spin-wave transport. Gallium-substituted yttrium iron garnet (Ga:YIG) offers a potential solution to these challenges due to its unique magnetic properties. The reduced saturation magnetization in Ga:YIG enables efficient excitation of exchange-dominated spin waves, which exhibit enhanced transport characteristics compared to dipolar-dominated modes in conventional materials. Here, we present the first comprehensive study combining experimental, analytical, and numerical investigations of spin-wave propagation in Ga:YIG waveguides down to 145 nm width and 73 nm thickness. Using micro-focused Brillouin light scattering spectroscopy, TetraX simulations, and analytical dispersion calculations, we demonstrate that Ga:YIG waveguides support spin waves with significantly higher group velocities up to 600 m/s. This value remains constant for structures with different widths, leading to longer spin-wave propagation lengths in nanowaveguides compared to non-substituted YIG. These results reveal that gallium substitution provides access to faster and longer-lived spin waves, opening new possibilities for implementing this material in nanoscale magnonic devices.

Power limiters are essential devices in modern rf communication systems to protect highly sensitive input channels from large incoming signals. Nowadays-used semiconductor limiters suffer from high electronic noise and switching delays when approaching the GHz range, which is crucial for the modern generation of 5G communication technologies aiming to operate at the EU 5G high band (24.25-27.5 GHz). The proposed solution is to use ferrite-based frequency selective limiters (FSLs), which maintain their efficiency at high GHz frequencies, although they have only been studied at the macroscale so far. In this study, we demonstrate a proof of concept of nanoscale FSLs. The devices are based on spin-wave transmission affected by four-magnon scattering phenomena in a 97-nm-thin yttrium iron garnet (YIG) film. Spin waves were excited and detected using coplanar waveguide (CPW) transducers of the smallest feature size of 250 nm. The FSLs are tested in the frequency range up to 25 GHz, and the key parameters are extracted (power threshold, power limiting level, insertion losses, bandwidth) for different spin-wave modes and transducer lengths. An analytical theory has been formulated to describe the fundamental physical processes, and a numerical model has been developed to quantitatively describe the insertion losses and power characteristics of the FSLs. Additionally, the perspective of the spin-wave devices is discussed, including the possibility of simultaneously integrating three devices into one: a frequency-selective limiter, an rf filter, and a delay line, allowing for more efficient use of space and energy.

Spin-transfer-torque and spin-orbit-torque nanooscillators (STNOs) are fundamentally nonlinear devices interesting for various applications in spintronics and microwave micro- and nanoelectronics. While the simplest, single-mode, generation regime of STNO is well-studied, the more complex regimes involving the generation of two or more spin wave modes simultaneously, which were observed in laboratory experiments, were not systematically analyzed in theory, so far. In this work, we analyze a two-mode generation regime in an STNO using a general model, which accounts for the inter-mode interactions, inevitably present in any STNO: mode competition for common (shared) pumping energy and, also, self- and cross-mode nonlinear frequency shift and nonlinear damping. It is shown that the key parameter governing the two-mode generation regime is the cross-mode coupling, which can be simplistically understood as being proportional to the spatial overlap of the profiles of interacting modes. In addition to the self-oscillation regime, the phase-locking of the self-generated modes to an external periodic force is studied, showing in some cases nontrivial dynamics.

Magnetic materials are familiar with their nonlinear dynamics, which becomes especially rich and efficient at the nanoscale. Precise control of nonlinear interaction is of high interest for various applications. Recently, it was shown that controllable symmetry breaking of magnetic state, induced, e.g., by a magnetic field perturbation, provides an efficient tool for manipulation of multi-magnon processes, which is especially efficient for three-magnon splitting and confluence. In this work, we investigate the effect of interfacial Dzyaloshinskii–Moriya interaction (IDMI)—an antisymmetric exchange interaction—on three-magnon processes. It is shown that IDMI affects the selection rules for three-magnon processes and their efficiency in all the considered geometries of thin magnetic nanodots: saturated magnetic dot with in-plane or perpendicular magnetization and vortex-state magnetic disk. Our results show the need for accurate consideration of possible effects of IDMI or other non-symmetric interactions when designing magnetic or spintronic devices with a controllable nonlinear response.

Magnon spintronics is an emerging field that explores the use of magnons, the quanta of spin waves in magnetic materials for information processing and communication. Achieving unidirectional information transport with fast switching capability is critical for the development of fast integrated magnonic circuits, which offer significant advantages in high-speed, low-power information processing. However, previous unidirectional information transport has primarily focused on Damon-Eshbach spin-wave modes, which are nonswitchable as their propagation direction is defined by the direction of the external field and cannot be changed in a short time. Here, we experimentally demonstrate a fast switchable unidirectional magnon emitter in the forward-volume spin-wave mode by a current-induced asymmetric Oersted field. Our findings reveal significant nonreciprocity and nanosecond switchability, underscoring the potential of the method to advance high-speed spin-wave processing networks.

Quantum magnonics aims to exploit the quantum mechanical properties of magnons for nanoscale quantum information technologies. Ferrimagnetic yttrium iron garnet (YIG), which offers the longest magnon lifetimes, is a key material typically grown on gadolinium gallium garnet (GGG) substrates for structural compatibility. However, the increased magnetic damping in YIG/GGG systems below 50K poses a challenge for quantum applications. Here, we study the damping in a 97nm-thick YIG film on a 500μm-thick GGG substrate at temperatures down to 30mK using ferromagnetic resonance (FMR) spectroscopy. We show that the dominant physical mechanism for the observed tenfold increase in FMR linewidth at millikelvin temperatures is the non-uniform bias magnetic field generated by the partially magnetized paramagnetic GGG substrate. Numerical simulations and analytical theory show that the GGG-driven linewidth enhancement can reach up to 6.7 times. In addition, at low temperatures and frequencies above 18GHz and temperatures below 2K and frequencies above 10GHz, the FMR linewidth deviates from the viscous Gilbert-damping model. These results allow the partial elimination of the damping mechanisms attributed to GGG, which is necessary for the advancement of solid-state quantum technologies.

We present a study of the magnetic properties of circular nanodots placed inside or in the vicinity of a circular hole in the perpendicularly magnetized antidot matrix. Micromagnetic simulations were performed to investigate the remanent magnetization configurations of the nanodots as a function of their vertical position relative to the matrix. The results demonstrate that the strength of the radial component of antidot matrix stray fields varies significantly along the vertical coordinate. This change influences the remanent state of nanodots, leading, depending on their location, to the stabilization of several magnetization configurations: radial vortex, curled vortex, or single-domain state. It was found that placing the dot at few nanometers below or above the matrix allows to stabilize the vortex state for a nanodot with the smallest diameter. This result provides a hint to tailor the magnetic properties of nanodots for their applications in spintronic and magnonic devices.