Spin waves, quantized as magnons, constitute a fundamental class of excitations and serve as one of the primary angular momentum carriers in magnetic systems. Devoid of Joule heating, a magnonic device that routes spin waves between different ports holds promise for an energy-efficient information infrastructure. Here, we systematically investigate the transport behavior of a magnetic skyrmion-based magnon circulator, a representative device that directs spin wave flow in a non-reciprocal manner. Particularly, a ballistic transport model is established, where the scattering of spin waves by magnetic skyrmions is simplified as magnon deflection by fictitious electromagnetic fields within the skyrmions. Through the combination of ballistic analyses and micromagnetic simulations, the circulation performance is rigorously evaluated for multiple magnon circulators.

Magnetic solitons are nonlinear, local excitations in magnetic systems. In this study, we theoretically and numerically investigate the properties and generation of one-dimensional (1D) topologically trivial magnetic solitons in ferromagnetic nanowires. An approximate analytical soliton solution described by two free parameters is validated by comparison with the micromagnetic simulation. Across an interface between two media of different anisotropy, the reflection and refraction of a soliton are highly nonlinear, which differ from linear spin waves. A pair of magnetic solitons that propagate in opposite directions can be generated by alternately applying magnetic-field or spin-polarized-current pulses of opposite directions to at least two successive regions. Each soliton corresponds to a soliton solution that can be controlled by the generation process. These magnetic solitons can be used to drive domain wall motion over a distance determined by the soliton magnitude, allowing for discrete manipulation of domain walls compatible with the digital nature of information technology. Our findings pave the way for the application of topologically trivial solitons in spintronics.

The growing demand for artificial intelligence and complex computing has underscored the urgent need for advanced data storage technologies. Spin-orbit torque (SOT) has emerged as a leading candidate for high-speed, high-density magnetic random-access memory due to its ultrafast switching speed and low power consumption. This review systematically explores the generation and switching mechanisms of electron-mediated torques (including both conventional SOTs and orbital torques) and magnon-mediated torques. We discuss key materials that enable these effects: heavy metals, topological insulators, low-crystal-symmetry materials, non-collinear antiferromagnets, and altermagnets for conventional SOTs; 3d, 4d, and 5d transition metals for orbital torques; and antiferromagnetic insulator NiO- and multiferroic BiFeO$_{3}$-based sandwich structures for magnon torques. We emphasize that although key components of SOT devices have been demonstrated, numerous promising materials and critical questions regarding their underlying mechanisms remain to be explored. Therefore, this field represents a dynamic and rapidly evolving frontier in spintronics, offering significant potential for advancing next-generation information storage and computational technologies.

Magnetic nanostructures with nonhomogeneous magnetic properties exhibit distinct magnon modes, and their interactions are crucial for understanding magnetization dynamics. In this work, we numerically investigate the magnon-magnon coupling in a nanodisk with radially varying magnetic anisotropy by using micromagnetic simulations. By introducing perpendicular magnetic anisotropy into the inner region of the nanodisk, a radially chiral spin texture is observed. The presence of the chiral spin texture results in coupling between the ferromagnetic resonance mode of the whole disk and the higher-order confined modes in the outer region. Moreover, we find that the coupling strength is highly sensitive to the perpendicular magnetic anisotropy, the saturation magnetization, and the interfacial Dzyaloshinskii-Moriya interaction. Our findings could enrich the understanding of the dynamic characteristics of chiral nanomagnets and suggest a possible route to harnessing tunable magnon-magnon coupling for spin-based quantum information processing.

The magnons (the quanta of collective spin-wave excitations) in two-dimensional van der Waals (vdW) magnets exhibit some intriguing characteristics, such as spin Nernst effect, topological magnons, Weyl magnons, moiré magnons, magnon valley Hall effect, etc., and can be regulated through approaches such as stacking, electric doping, pressure, strain and twisting, opening unprecedented avenues to explore fundamental magnetic physics and spin-based technologies. Over the past few years, intense research efforts have been invested in unraveling magnon properties in vdW materials. This review comprehensively summarizes recent advancements in understanding magnons in vdW magnetic systems, spanning fundamental theories and experimental frontiers. It also introduces the experimental techniques widely used in this field, including inelastic neutron scattering, Raman/Brillouin spectroscopy, time-resolved spectroscopy and inelastic magneto-tunneling spectroscopy, and discusses the coupling between magnons and other excitations, such as phonons and excitons.

In antiferromagnets, dipolar coupling is often disregarded due to the cancellation of magnetic moments between the two sublattices, so that the spin-wave dispersion is predominantly determined by exchange interactions. However, antiferromagnetic spin waves typically involve a slight misalignment of the magnetic moments on the sublattices, which gives rise to a small net magnetization enabling long-range dipolar coupling. In this paper, we investigate the role of dipolar coupling in spin-wave excitations and its influence on the resulting dispersion. Our findings show that: (i) when the Néel vector is perpendicular to the film plane or lies within the film plane and parallel to the wave vector, the dispersion branches can be divided into two groups: those unaffected by the dipolar field and those influenced by it. In these cases, the total magnetic moment remains linearly polarized, but the polarization directions differ between the two types of branches; (ii) when the Néel vector lies in the film plane and is perpendicular to the wave vector, the dipolar interactions affect both types of dispersion branches, leading to their hybridization. This hybridization alters the polarization of the magnetic moment, resulting in elliptical polarization.

Strong coupling effects in magnonic systems are highly promising. They combine the advantages of different quasiparticles and enable energy transfer for coherent information processing. When driven by microwave, electric, or optical pumps, these coupling effects can give rise to intriguing nonlinear phenomena, which have become a focal point in the field of magnonics. This review systematically explores pump-engineered magnon-coupling systems from three perspectives: (1) pump-induced hybridization of magnon modes, (2) nonlinear manipulation of magnon dynamics, and (3) implementation of functional magnonic devices. Unlike conventional cavity-magnon interactions that are constrained by electromagnetic boundaries, pumped coupled magnons are liberated from these restrictions. They can operate over a broad frequency band rather than being confined to discrete modes. An example is the recently discovered pump-induced magnon mode (PIM). These magnons arise from the collective excitations of unsaturated spins driven by microwave pumps. They exhibit reduced damping and photon-number-sensitive splitting characteristics, facilitating waveform-controlled coupling strength and enhanced nonlinearity - features that support phenomena such as magnonic frequency combs (MFCs). By expanding this principle to electric pumping schemes, we bridge fundamental physics and practical device applications, enabling nonreciprocal switching and meter-scale strong coupling. These advances establish high-dimensional control capabilities for coupled magnonics and pave the way for their use as a promising platform for dynamically programmable devices, magnetic-field sensing, and coherent networks.

Magnonics and magnonic materials have attracted widespread interest in the spintronics community and demonstrate potential for applications in the next generation of information technology. Recent advances in manganite thin films highlight their promise for magnonics, in which enhanced film quality and strain control of spin and electronic structures play a crucial role in reducing magnetic damping. Here, we report the fabrication of La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ thin films of varying quality via pulsed laser deposition. The quality of epitaxial films is characterized using atomic force microscopy and x-ray diffraction. A pronounced fourfold anisotropy in the magnetic damping (with a ratio of about 150%) is observed, where the minimum damping occurs along the [110] crystalline orientation. Notably, improved sample quality significantly reduces the magnetic damping at low temperatures. The highest-quality sample, featuring atomic-scale terraces, exhibits a magnetic damping of $\sim 2.5\times 10^{-3}$ at 5 K. Our results not only demonstrate effective reduction of low-temperature magnetic damping in high-quality correlated oxide systems but also provides a strategy and material platform for exploring novel quantum phenomena and for designing low-temperature magnonic devices.

We investigate the inertial domain wall (DW) dynamics driven by spin-polarized current in ferromagnets. The exact solutions reveal an upper limit for DW velocity, given by $V\leq1/\sqrt{\alpha \tau}$. This indicates that damping and inertia become the key factors in achieving higher DW speeds. For the case of uniaxial anisotropy, we analyze the effects of inertia and current on DW dynamics. Due to inertia, the DW velocity, width, rotation frequency, and wave number are mutually coupled. When the DW width varies slightly, the velocity decreases rapidly while the magnetization precession frequency increases sharply with the inertia term. However, once the rotation frequency exceeds its maximum value, both the DW velocity and rotation frequency gradually decline. Regarding current-driven dynamics, we identify a critical current $j_{\rm 1c}$ that directly triggers the Walker breakdown. For currents below this threshold $j_{1}<j_{\rm 1c}$, the absolute DW velocity increases with current, whereas it decreases for $j_{1}>j_{\rm 1c}$. During this process, the DW velocity rapidly peaks under current drive, accompanied by the magnetization rotation frequency nearing its maximum and minimal variation in DW width. These results suggest that the DW behaves like a classical rigid body, reaching its maximum velocity as it approaches peak rotational speed. For biaxial anisotropy, we derive analytical solutions. The competition between hard-axis anisotropy and inertia causes the DW magnetization to lose its spiral structure and rotational symmetry. The inertia effect leads to a slow initial decrease followed by a rapid increase in DW width, whereas current modulation gradually widens the DW. The analytical solution also reveals another critical current, $j_{1\max}=\sqrt{\alpha/\tau}/\beta$, which scales with the square root of the inertia-to-damping ratio and is inversely proportional to the nonadiabatic spin-transfer torque parameter $\beta$.

We theoretically demonstrate that multipartite entanglement and one-way Einstein-Podolsky-Rosen (EPR) steering in a magnon frequency comb (MFC) can be generated in a hybrid magnon-skyrmion system. When the system is driven by two microwave fields at the magnonic whispering gallery mode (mWGM) and the skyrmion, the skyrmion can be simultaneously entangled with three magnon modes of the MFC and the entanglement of the first-order magnon pair in the MFC also appears. The results show that the perfect one-way steering between the skyrmion and the three magnons can be obtained. Interestingly, the steering direction can be manipulated by controlling the amplitudes of two drive fields, which provides flexibility in controlling the asymmetry of the EPR steering and may well have practical applications. Moreover, the genuine tripartite entanglement among the skyrmion and the first-order magnon pair can be achieved with appropriate parameters in the steady state. Our work exhibits that the MFC has great potential in preparing multi-mode entanglement resources, with promising applications in quantum communication.

Spin waves in van der Waals magnets hold promise for magnonic devices and circuits down to the two-dimensional limit. However, their short decay lengths pose challenges for practical applications. Here, we report on a material platform consisting of a van der Waals magnet, Fe$_5$GeTe$_2$ (FGT), and a ferrimagnetic insulator of yttrium iron garnet, Y$_3$Fe$_5$O$_{12}$ (YIG), which supports the low-loss propagation of spin waves. Using broadband spin-wave spectroscopy, we observed an increase in spin-wave group velocity with decreasing temperature, which peaks at 30 K in the YIG and FGT/YIG films. This effect is ascribed to a change in the saturation magnetization of YIG and FGT/YIG at low temperature, resulting in a change in the spin-wave dispersion relations. Using micromagnetic simulations, we further investigated spin-wave propagation in an FGT/YIG bilayer and revealed a longer spin-wave decay length in the bilayer than in a single FGT layer, which is due to the lower effective damping in the bilayer. Moreover, asymmetric spin-wave dispersion, induced by a chiral dipolar interaction between the YIG and FGT layers, enables nonreciprocal control of spin-wave propagation.

Magnon frequency combs have garnered significant attention due to their wide-ranging potential applications, primarily generated by the interplay between spin waves and oscillating magnetic textures. Developing an easily achievable magnon frequency comb with directly tunable comb spacing is pivotal for broadening its utility. In this study, we engineered a Bloch-type magnetic domain wall with a stable structure and fixed position by employing a dual-pinning approach utilizing artificial structural defects and stray fields. We established a magnetic domain wall oscillation mode based on resonant Larmor precession, serving as the foundation for a magnon frequency comb derived from magnetic domain walls. By leveraging the locally distributed Oersted field generated by an alternating current, we achieved precise control over the oscillation frequency of the domain wall, thereby realizing a magnon frequency comb with directly tunable comb spacing. The insights from this research offer a promising shortcut for exploring frequency combs based on the interaction between spin waves and magnetic domain walls.

Magnetostrictive effects and magnetocrystalline anisotropy are fundamental physical properties governing magnon dynamics in magnetic systems. Recent evidence shows that strain-mediated magnetostrictive coupling provides an effective pathway for modulating magnonic excitation through quantum interference. Nevertheless, the microscopic origins of magnetocrystalline anisotropy in manipulating magnon excitation pathways, particularly regarding magnonic Kerr nonlinearity and crystal direction constraints, require further investigation. In this study, we construct a dual-frequency driven magnomechanical model based on yttrium iron garnet (YIG) spheres. By introducing a Hamiltonian with the magnonic Kerr nonlinear term, we combine the Heisenberg-Langevin equations and the mean field approximation to analytically solve for the driving efficiency $\eta$, and we base our analysis on experimental parameters to evaluate the impacts of the magnonic Kerr coefficient ($K$), driving field ($B_1$) and YIG size. The results show that the magnetocrystalline anisotropy induces a MHz-scale frequency shift, splitting the transmission spectrum from a Lorentzian line shape into asymmetric Fano resonance double peaks. The orientation of the external magnetic field (aligned with the [100] or [110] crystallographic axis) allows precise control over the sign of the magnonic Kerr coefficient $K$, thereby enabling a reversal in the direction of the frequency shift. A strong driving field $B_1$ not only enables controllable switching of the state but also adjusts the switching bandwidth. Furthermore, we show the transition of the dynamical response mechanism of the excitation efficiency spectrum with varying YIG sphere sizes. The study shows the dynamic control mechanism of the magnetocrystalline anisotropy on magnon switching and provides a theoretical foundation for size optimization and nonlinear energy manipulation in spintronic device design.

A cavity magnonic oscillator uses the coupling of a planar transmission line oscillator (cavity) and spin excitations (magnons) in a ferrimagnetic material to achieve superior frequency stability and reduced phase noise. Like many low phase noise oscillators, a cavity magnonic oscillator faces the challenge that its narrow resonance profile is not well suited for injection locking amplification. This work presents an improved design for such an oscillator configured as an injection locking amplifier (ILA) with an extended lock range. The proposed design features a two-stage architecture, consisting of a pre-amplification oscillator and a cavity magnonic oscillator, separated by an isolator to prevent backward locking. By optimizing the circuit parameters of each stage, the proposed design achieved an order of magnitude increase in lock range, when compared to its predecessors, all while preserving the phase noise quality of the input, making it well-suited for narrowband, sensitive signal amplification. Furthermore, this work provides a method for using oscillators with high spectral purity as injection locking amplifiers.

We utilize conventional wave-vector-resolved Brillouin light scattering technology to investigate the spin wave response in YIG thin films under high-power microwave excitation. By varying the microwave frequency, external bias magnetic field, and in-plane wave vector, in addition to observing the dipole-exchange spin waves excited by parallel parametric pumping, we further observe broadband spin wave excitation within the dipole-exchange spin wave spectrum. This broadband excitation results from the combined effects of parallel and perpendicular parametric pumping, induced by irregularities in the excitation geometry, as well as magnon-magnon scattering arising from the absence of certain spin wave modes. Our findings offer new insights into the mechanisms of energy dissipation and relaxation processes caused by spin wave excitation in magnetic devices operating at high power.

We report the bifurcation of bound states in the continuum (BICs) in a dissipative cavity magnonic system, where a BIC splits into a pair of BICs. We theoretically analyze BICs in a dissipative cavity magnonic system and derive the critical condition for BICs bifurcation. Based on the theoretical results, we experimentally tune the dissipative photon-magnon coupling strength and demonstrate precise control over the detuning and number of BICs. When the dissipative coupling strength reaches a critical value, we observe the bifurcation of BICs, which is consistent with the theoretical prediction. Our systematic investigation of the evolution of BICs concerning the dissipative coupling strength and the discovery of the BIC bifurcation may enhance the sensitivity of BICs to external perturbations, potentially enabling applications in ultrasensitive detection.

We investigate magnonic topology in the breathing Su-Schrieffer-Heeger (SSH) model, incorporating non-Hermitian effects. Our results demonstrate the coexistence of first- and second-order magnonic topologies, with non-Hermitian effects exhibiting size-dependent behavior. In two-dimensional systems, non-Hermitian terms induce a flat band and gap closure along high-symmetry paths, whereas in one-dimensional systems, a finite band gap persists for small system sizes. Additionally, the corner states remain robust, and a pronounced non-Hermitian skin effect emerges. Our findings provide new insights into magnon-based devices, emphasizing the impact of non-Hermitian effects on their design and functionality.

We report a theoretical analysis of magnon-magnon coupling in a noncollinear magnetic sandwiched structure with interlayer exchange interaction, which consists of two ferromagnetic layers with perpendicular and in-plane magnetic anisotropy, respectively. Based on the Landau-Lifshitz equation, the spin wave dispersion is derived, and then the frequency gap is observed due to the magnon-magnon coupling effect induced by symmetry breaking. The influence of saturation magnetization, exchange coupling interaction, perpendicular magnetic anisotropy, and wave vector on the coupling strength is studied in detail. We find that the coupling strength is strongly dependent on the saturation magnetization and a small saturation magnetization can lead to strong coupling strength. By selecting the appropriate magnetic materials, the ultra-strong coupling regime can be achieved. The precession information in time domain is solved and the alternating change of the precession components in two ferromagnetic layers implies the exchange of energy and information.

Microwave-optical entanglement is essential for efficient quantum communication, secure information transfer, and integrating microwave and optical quantum systems to advance hybrid quantum technologies. In this work, we demonstrate how the magnon Kerr effect can be harnessed to generate and control nonreciprocal entanglement in cavity optomagnomechanics (COMM). This effect induces magnon frequency shifts and introduces pair-magnon interactions, both of which are tunable through the magnetic field direction, enabling nonreciprocal behavior. By adjusting system parameters such as magnon frequency detuning, we show that magnon-phonon, microwave-optical photon-photon, and optical photon-magnon entanglement can be nonreciprocally enhanced and rendered more robust against thermal noise. Additionally, the nonreciprocity of entanglement can be selectively controlled, and ideal nonreciprocal entanglement is achievable. This work paves the way for designing nonreciprocal quantum devices across the microwave and optical regimes, leveraging the unique properties of the magnon Kerr effect in COMM.