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Magnetic vortices are being considered for information storage in magnetic devices. In this study, we used micromagnetic simulations to explore the effect of a perpendicular uniaxial anisotropy (PUA) on switching the vortex core in Permalloy nanodisks. We studied how the presence of the perpendicular uniaxial anisotropy (PUA) changes the spatial profile of the magnetic vortex. We determined the diameters of the vortex core as the perpendicular uniaxial anisotropy constant K z varied. Additionally, we determined the frequencies and spatial profiles of the radial modes of the spin waves. Our results show that the PUA affects the frequencies of the spin modes of a magnetic vortex in a nanodisk. We have also created phase diagrams demonstrating the areas where reversing the magnetic vortex core is possible by applying a sinusoidal field perpendicular to the nanodisk plane. [ABSTRACT FROM AUTHOR]

Coupling between spin waves (SWs) and other types of waves in nanostructured magnetic media has attracted increased attention in recent years because of the rich physics and the potential to spawn disruptive technologies. Among this family of intriguing phenomena, we recently reported a new one: coupling between SWs and hybridized phonon–plasmon waves, resulting in tripartite coupling of magnons, phonons, and plasmons. Here, this acousto-plasmo-magnonic phenomenon is studied in a two-dimensional periodic array of bilayered Co/Al nanodots on a silicon substrate, where Co is a magnetostrictive constituent responsive to magnetoelastic coupling and Al acts as a source of surface plasmons. Time-resolved magneto-optical-Kerr-effect microscopy revealed parametric amplification and strong coupling between two SW modes mediated by a hybrid phonon–plasmon mode. The strong coupling forms a new quasi-particle: the phonon–plasmon–magnon polariton. [ABSTRACT FROM AUTHOR]

Alloying germanium with tin offers a means to modulate germanium's electronic structure, enabling a greater degree of control over quantum properties such as the retention of the phase or spin of the electron wave. However, the extent to which the presence of high dopant concentrations in GeSn alters these quantum behaviors is poorly understood. Here, we investigate the role of dopant concentrations on phase coherence through measurements of the weak antilocalization (WAL) effect at temperatures between 30 mK and 10 K in p-GeSn (8%) thin films, which were doped to a series of carrier densities on the order of 10 12 c m − 2 . Phase coherence and spin–orbit lengths were extracted from the magnetoconductivities using the 2D Hikami–Larkin–Nagaoka model. Phase coherence lengths peaked at 577, 593, and 737 nm for the low-, mid-, and high-density samples, while upper limits on the spin–orbit lengths of less than 25 nm were relatively independent of carrier density and temperature. The phase coherence lengths increased as the temperature decreased but changed only minimally with carrier density, contrary to common models of temperature-dependent inelastic scattering. Saturation of the phase coherence lengths occurred below 600 mK. Based on these findings, intrinsically generated inelastic scattering mechanisms such as two-level systems or impurity band scattering likely contribute to phase decoherence in these alloys. Our results provide insight into the inelastic scattering mechanisms of GeSn, while suggesting a need for further investigation into phase decoherence mechanisms in doped group-IV alloys. [ABSTRACT FROM AUTHOR]

Ferromagnetic nanowires are receiving attention as functional elements in technologically important applications in microwave devices, spintronics, and biomedicine. They can be readily fabricated over large areas using electrodeposition, and their magnetic response can be tuned through control of their size, geometry, and composition. Additionally, their geometrical properties provide a stable spin structure for manipulating magnetization dynamics using spin-polarized currents for spintronic applications. Structural analysis of individual cobalt nanowires indicated magnetocrystalline anisotropy predominantly perpendicular to the nanowire axis. This significantly alters the micromagnetic energy landscape in the nanowire and breaks the circular symmetry of the dynamic magnetization and resonance modes which is often assumed in theory. In this article, we investigate, using finite-element micromagnetic–electromagnetic simulations, the effect of the variation of magnetocrystalline anisotropy angle on the dynamic magnetization in the nanowire and leads to a shift in the resonance frequencies and modes. The resonance is induced by a pulsed electric current applied along the nanowire axis and simulations include the contributions of magnetocrystalline anisotropy, exchange, dipolar fields, and eddy currents. Understanding the magnetization dynamics induced by electric currents and spin-wave modes in metallic magnetic nanowires and their size and anisotropy angle dependence is important for the design and tuning of magnetic nanowire arrays and devices. [ABSTRACT FROM AUTHOR]

Spin-Hall nano-oscillators (SHNOs) are nanoscale spintronic devices that generate high-frequency (GHz) microwave signals useful for various applications, such as neuromorphic computing and creating Ising systems. Recent research demonstrated that hybrid SHNOs consisting of a ferromagnetic metal (permalloy) and lithium ferrite-based (LAFO) insulating ferrimagnetic thin films have advantages in having lower auto-oscillation threshold currents (I th) and generating larger microwave output power, making this hybrid structure an attractive candidate for spintronic applications. It is essential to understand how the tunable material properties of LAFO, e.g., its thickness, perpendicular magnetic anisotropy (K u , LAFO ), and saturation magnetization (M s , LAFO ), affect magnetic dynamics in hybrid SHNOs. We investigate the change in I th and the output power of the device as the LAFO parameters vary. We find the I th does not depend strongly on these parameters, but the output power has a highly nonlinear dependence on M s , LAFO and K u , LAFO . We further investigate the nature of the excited spin-wave modes as a function of K u , LAFO and determine a critical value of K u , LAFO above which propagating spin-waves are excited. Our simulation results provide a roadmap for designing hybrid SHNOs to achieve targeted spin excitation characteristics. [ABSTRACT FROM AUTHOR]

In this study, we report giant nonreciprocal transmission of shear-horizontal surface acoustic waves (SH-SAWs) in a ferromagnetic bilayer structure with negative–positive magnetostriction configuration. Although the directions of magnetization in the neighboring layers are parallel, SH-SAWs can excite optical-mode spin waves (SWs) via magnetoelastic coupling at relatively low frequencies, which is much stronger than acoustic-mode SWs at high frequencies. The measured magnitude nonreciprocity or isolation of SH-SAWs exceeds 40 dB (or 80 dB/mm) at 2.333 GHz. In addition, maximum nonreciprocal phase accumulation reaches 188° (376°/mm). Our theoretical model and calculations provide an insight into the observed phenomena and demonstrate a pathway for further improving nonreciprocal acoustic devices toward highly compact microwave isolators and circulators. [ABSTRACT FROM AUTHOR]

Spin waves, collective perturbations of magnetic moments, are both fundamental probes for magnetic physics and promising candidates for energy-efficient signal processing and computation. Traditionally, coherent propagating spin waves have been generated by radio frequency (RF) inductive Oersted fields from current-carrying electrodes. An alternative mechanism, spin–orbit torque (SOT), offers more localized excitation through interfacial spin accumulation but has been mostly limited to DC to kHz frequencies. SOT driven by RF currents, with potentially enhanced pumping efficiency and unique spin dynamics, remains largely unexplored, especially in magnetic insulators. Here, we conduct a comprehensive theoretical and computational investigation into the generation of coherent spin waves via RF-SOT in the prototypical yttrium iron garnet. We characterize the excitation of forward volume, backward volume, and surface modes in both linear and nonlinear regimes, employing single and interdigitated electrode configurations. We reveal and explain several unique and surprising features of RF-SOT compared to inductive excitation, including higher efficiency, distinct mode selectivity, and directional symmetry, a ∼ 3 π / 4 phase offset, reduced anharmonic distortion in the nonlinear regime, and the absence of second harmonic generation. These insights position RF-SOT as a promising new mechanism for future magnonic and spintronic applications. [ABSTRACT FROM AUTHOR]

We report the effect of thickness and width on the spin wave transport and dispersion characteristics of permalloy (Py) microstripes using analytical calculations and experiments. Py waveguides with widths ranging from 2 to 4 μm were fabricated for two different thicknesses: 5 and 20 nm. Our results show a notable increase in the group velocity of spin waves with greater thickness, showing a fourfold rise as the thickness increases. Additionally, the accessible frequency range expands from 0.6 to 2.5 GHz as the thickness increases. We find that the spin wave mode frequency is affected by both thickness and width, with a frequency shift of approximately 0.2 GHz observed when the width increases from 2 to 4 μm. Moreover, spin waves decay more rapidly in thinner films, with the decay length of 20 nm-thick waveguides being four times longer than that of 5 nm-thick waveguides. Thicker and wider waveguides provide a longer decay length, facilitating the transmission of information over longer distances without significant energy loss. Our study offers an understanding of the spin wave propagation in microstrip waveguides and its potential in the development of future magnonic devices. [ABSTRACT FROM AUTHOR]

Micromagnetic simulations are used to investigate the effect of an external magnetic field on the interaction between domain walls and linearly polarized propagating spin waves in synthetic antiferromagnets. Two regimes with a sharp transition between them are found. At large fields, spin waves are strongly reflected by the domain wall and, consequently, the latter is propelled forward. At low fields, however, there is no reflection and yet the domain wall undergoes a small forward displacement, which is attributed to the change in linear momentum of the magnons as they pass through the domain wall and to the imbalance in the population of the two oscillation modes present in the linearly polarized excitation. The transition between the two regimes occurs at the field value for which the excitation frequency falls below the threshold of the high-frequency mode. [ABSTRACT FROM AUTHOR]

We present a concept for selective excitation of magnetostatic surface waves with a quasi-discrete spectrum using spatially patterned femtosecond laser pulses inducing either an ultrafast change of magnetic anisotropy or an inverse Faraday effect. We micromagnetically simulate the excitation of the waves with a periodically patterned uni- or bipolar laser impact. Such excitation yields multiple wavepackets propagating with different group velocities, whose dispersion corresponds to the set of quasi-discrete points. In addition, we show that the frequency of the spectral peaks can be controlled by the polarity of the periodic impact and its spatial period. The presented consideration of multiple spatially periodic magnetostatic surface wave sources as a whole enables implementation of a comprehensive toolkit of spatiotemporal optical methods for tunable excitation and control of spin-wave parameters. [ABSTRACT FROM AUTHOR]

As one of the fundamental magnonic devices, magnonic splitter devices have been proposed and spin wave propagation in the devices has been studied numerically and experimentally. In the present work, we fabricated a T-shaped magnonic splitter with three 6 μm-wide arms from a 100 nm-thick yttrium iron garnet film. Using time-resolved magneto-optic Kerr microscopy, we observed spin waves splitting into both, the vertical and the horizontal direction at the junction. Analyzing the results, we found that the spin wave width modes are converted into each other during the splitting process and, consequently, concluded that the width mode conversion efficiency depends on the ratio of wavelength to the vertical branch's width and the anisotropic distribution of the spin wave amplitude at the T-junction. [ABSTRACT FROM AUTHOR]

In this study, we discuss the observation of spin-wave interference generated by magnetic oscillators. We employ micromagnetic simulations for two coherent spin-Hall nanowire oscillators positioned nearby, horizontally or vertically. The two nanowires produce circular waves with short wavelengths on the order of 100 nm, which interfere with each other. In the horizontal configuration, the spin waves exhibit constructive and destructive fringes, indicating amplification or cancellation of the amplitudes, respectively. The synchronization of spin waves in the current geometry of the two nanowires is facilitated by the combination of dipolar fields and propagating spin waves. Additionally, the vertical alignment results in standing spin waves characterized by multiple antinodes and nodes. These observations are interpreted using a wave model that incorporates the superposition principle for each case. [ABSTRACT FROM AUTHOR]

A numerical model describing a magnonic active ring oscillator (MARO) based on a microscopic spin-wave delay line is proposed. The model considers excitation, propagation, and reception of the magnetostatic surface waves in a yttrium iron garnet (YIG) magnetic film with a thickness in the nanometer range. The waves are excited and received with a microscopic coplanar antenna. We employed the model to analyze the influence of the YIG-film thickness and the distance between the antennas on the MARO performance characteristics. We showed that an increase in the delay time inserted by the delay line reduces the phase noise of the MARO and increases the auto-oscillation threshold. In addition, we found a relation between the auto-oscillation threshold, the thickness of the YIG film, and the distance between the antennas. The relation helps design miniature MAROs and suggests a way to reduce the phase noise of the device. The model predicts a phase noise level of −115 dBc/Hz at a 10 kHz offset from an oscillation frequency in the vicinity of 5 GHz for the MARO based on a 100 nm-thick YIG film and 56 μm of distance between the coplanar nano-antennas of the YIG-film based delay line. We believe that this is a clear way forward to microminiaturize the time-delay feedback microwave auto-oscillators. A further reduction in the phase noise down to −125 dBc/Hz at a 10 kHz offset is found in a model of cascaded connection of several microscopic spin-wave delay lines. [ABSTRACT FROM AUTHOR]

In this work, we theoretically study the switching and oscillation dynamics in strained non-collinear antiferromagnet (AFM) Mn3X (X = Sn, Ge, etc.). Using the perturbation theory, we identify three separable dynamic modes—one uniform and two optical modes, for which we analytically derive the oscillation frequencies and effective damping. We also establish a compact, vector equation for describing the dynamics of the uniform mode, which is in analogy to the conventional Landau–Lifshitz–Gilbert (LLG) equation for ferromagnet but captures the unique features of the cluster octuple moment. Extending our model to include spatial inhomogeneity, we are able to describe the excitations of dissipative spin wave and spin superfluidity state in the non-collinear AFM. Furthermore, we carry out numerical simulations based on coupled LLG equations to verify the analytical results, where good agreements are reached. Our treatment with the perturbative approach provides a systematic tool for studying the dynamics of non-collinear AFM and is generalizable to other magnetic systems in which the Hamiltonian can be expressed in a hierarchy of energy scales. [ABSTRACT FROM AUTHOR]

We report on the field evolution of the microwave spin wave modes in magnonic crystals made of square antidot lattices etched in a thin film of the Co2MnSi Heusler alloy and having a lateral size s of 200 nm and an edge-to-edge separation d of 600 or 800 nm. The spin wave modes are investigated combining ferromagnetic resonance, Brillouin light scattering experiments, and micromagnetic simulations of the static and dynamic magnetic states as a function of the applied field. We show that for applied fields ≥10 mT, when the magnetization is quasi-saturated across the crystals, the two samples show similar behavior and the two most intense modes in the spin waves spectra correspond to a mode extending in the channels comprised between the antidot and a mode localized in the region between the antidots. For smaller fields, we observe a difference of the measured spectra as a function of d. This is attributed to the fact that for d = 800 nm, the magnetization remains partially uniform in the channel between the antidots because of the Heusler cubic crystal anisotropy, while for d = 600 nm, the magnetic edge domains around the antidots spread into the channels. Moreover, this anisotropy also allows different remanent states when initializing the crystals with a small magnetic field along two perpendicular directions. This leads to an efficient excitation or extinction of the spin wave modes, making possible to achieve reconfigurable microwave devices exploiting an antidot geometry in a metallic ferromagnetic with a low damping coefficient. [ABSTRACT FROM AUTHOR]

The recently proposed concept of electric chiral magnonic resonator (ECMR) has been extended to include usage of spin–orbit torques (SOT). Unlike the original version of ECMR which was based on voltage controlled magnetic anisotropy (VCMA), the spin wave amplification power by this new version of ECMR (pumped by SOT) no longer depends on the phase of the incident wave, which is highly desirable from an application point of view. The performance of the SOT pumped ECMR has been compared with the case of amplification by applying SOT pumping directly to a waveguide (without any ECMR involved). It is argued that at the expense of narrowing the bandwidth (i.e., slower amplifier response), the advantage of the former configuration (amplification by a SOT pumped ECMR) over the latter (amplification by direct SOT pumping the waveguide) is to offer gain, while at the same time, maintaining system stability (avoidance of auto-oscillations). Non-linear behavior of the SOT pumped ECMR has been analyzed. It is demonstrated that by cascading a SOT ECMR operating in an off-resonance mode together with a VCMA biased passive ECMR, it is possible to produce a magnonic neuron with a transmitted signal magnitude larger than the input in the firing state. [ABSTRACT FROM AUTHOR]

A numerical model for a spin wave delay-line active ring resonator is presented. Spin wave dynamics along a one-dimensional strip of magnetic material are modeled using the nonlinear Schrödinger equation. The equation is solved numerically in Fourier space using the fourth-order Runge–Kutta method and yields qualitative agreement with experimental measurements of spin wave dynamics in two different regimes. The model provides a useful tool for performing experiments based on neuromorphic computing and logic gates in traveling spin wave devices. [ABSTRACT FROM AUTHOR]

Using time as an additional design parameter in electromagnetism, photonics, and wave physics is attracting considerable research interest, motivated by the possibility to explore physical phenomena and engineering opportunities beyond the limits of time-invariant systems. Here, we report the experimental demonstration of enhanced broadband absorption of electromagnetic waves in a continuously modulated time-varying system, exceeding one of the key theoretical limits of linear time-invariant absorbers. This is achieved by harnessing the frequency-wave vector transitions and enhanced interference effects enabled by breaking both continuous space-and time-translation symmetries in a periodically time-modulated absorbing structure operating at radio frequencies. Furthermore, we demonstrate broadband coherent wave absorption using a secondary control wave, observing a nearly perfect, reconfigurable, antireflection effect over a broad continuous bandwidth. Our findings provide insights into enhanced wave absorption in time-varying scenarios and may enable the development of devices operating in a regime fundamentally beyond the reach of linear time-invariant systems. [ABSTRACT FROM AUTHOR]

Magnonics, which harnesses the unique properties of spin waves, offers promising advancements in data processing due to its broad frequency range, nonlinear dynamics, and scalability for on-chip integration. Effective information encoding in magnonic systems requires precise spatial and temporal control of spin waves. Here, we demonstrate the rapid optical control of spin-wave transport in hybrid magnonic-plasmonic structures. By using thermoplasmonic heating in yttrium iron garnet films integrated with gold nanodisk arrays, we achieve a suppression of spin-wave signals by 20 dB using single laser pulses lasting just a few hundred nanoseconds. Our results reveal a strong correlation between plasmonic light absorption and spin-wave manipulation, as supported by micromagnetic simulations that emphasize the crucial role of magnonic refraction. This study establishes thermoplasmonics as a powerful tool for controlling spin-wave propagation, bridging the fields of magnonics and plasmonics, and paving the way for the development of multifunctional hybrid magnonic devices. [ABSTRACT FROM AUTHOR]

Quadratic Lindbladians encompass a rich class of dissipative electronic and bosonic quantum systems, which have been predicted to host new and exotic physics. In this study, we develop a Lindblad-Keldysh spectroscopic response formalism for open quantum systems that elucidates their steady-state response properties and dissipative phase transitions via finite-frequency linear and non-linear probes. As illustrative examples, we utilize this formalism to calculate the (1) density and dynamic spin susceptibilities of a boundary driven XY model at and near criticality, (2) linear and non-linear optical responses in Bernal bilayer graphene coupled to dissipative leads, and (3) steady state susceptibilities in a bosonic optical lattice. We find that the XY model spin density wavelength diverges with critical exponent 1/2, and there are gapless dispersive modes in the dynamic spin response that originate from the underlying spin density wave order; additionally the dispersing modes of the weak and ultra-strong dissipation limits exhibit a striking correspondence since the boundary dissipators couple only weakly to the bulk in both cases. In the optical response of the Bernal bilayer, we find that the diamagnetic response can decrease with increasing occupation, as opposed to in closed systems where the response increases monotonically with occupation; we study the effect of second harmonic generation and shift current and find that these responses, forbidden in centrosymmetric closed systems, can manifest in these open systems as a result of dissipation. We compare this formalism to its equilibrium counterpart and draw analogies between these non-interacting open systems and strongly interacting closed systems. [ABSTRACT FROM AUTHOR]

The magnetic excitation spectrum of most high-temperature superconducting (HTSC) cuprates is hour-glass shaped. The observation of hour-glass spectra in the isostructural Sr-doped cobaltates La2−xSrxCoO4 gives rise to a deeper understanding of these spectra. So far, hour-glass spectra have been only observed in those systems that evolve from incommensurate magnetic peaks. Here, we report on the appearance of hour-glass spectra in oxygen-doped cobaltates La2CoO4+δ. The high-energy part of the hour-glass spectrum of oxygen doped cobaltates is extremely anisotropic with a very prominent stripe-like appearance not seen that clearly in purely Sr-doped compounds. A charge stripe scenario is evidenced by (polarized) neutron diffraction measurements and also corroborated by spin wave simulations. Our results indicate that charge stripes are the origin of the anisotropic stripe- or diamond-shaped high-energy part of the hour-glass spectrum. A link between hour-glass spectra and charge stripes could be of relevance for the physics in HTSC cuprates. The hour-glass magnetic excitation spectrum is a universal feature of most cuprate high-temperature superconductors, yet the exact origins are still debated. Here, using inelastic neutron scattering techniques, the authors report hour-glass magnetic spectra in an oxygen-doped cobaltate La2CoO4+δ and discuss the potential link with charge stripes and the "diamond-shaped" high energy part of the hour-glass spectrum of this system. [ABSTRACT FROM AUTHOR]

We considered a domain wall as a structure which shifts the phase of a propagating spin wave under the condition of applied electric field by means of an inhomogeneous magnetoelectric coupling. The result is that the electrically induced transition of the Bloch domain wall into the Néel domain wall changes the phase of spin wave passed through the domain wall by nearly 180°. [ABSTRACT FROM AUTHOR]

We define predictive states and predictive complexity for quantum systems composed of distinct subsystems. This complexity is a generalization of entanglement entropy. It is inspired by the statistical or forecasting complexity of predictive state analysis of stochastic and complex systems theory but is intrinsically quantum. Predictive states of a subsystem are formed by equivalence classes of state vectors in the exterior Hilbert space that effectively predict the same future behavior of that subsystem for some time. As an illustrative example, we present calculations in the dynamics of an isotropic Heisenberg model spin chain and show that, in comparison to the entanglement entropy, the predictive complexity better signifies dynamically important events, such as magnon collisions. It can also serve as a local order parameter that can distinguish long and short range entanglement. [ABSTRACT FROM AUTHOR]

In this paper, we analyzed the influence of the spin Nernst effect on quantum correlation in a layered ferrimagnetic model. In the study of three-dimensional ferrimagnets, the focus is on materials with a specific arrangement of spins, where the neighboring spins are parallel and the others are antiparallel. The anisotropic nature of these materials means that the interactions between spins depend on their relative orientations in different directions. We analyzed the effect of magnon bands induced by the coupling parameters on entanglement negativity. The influence of the coupling parameters of the topologic phase transition on quantum entanglement is investigated as well. Numerical simulations using the Lanczos algorithm and exact diagonalization for different lattice sizes are compared with the results of spin wave theory. [ABSTRACT FROM AUTHOR]

The spin wave spectra and magnetic moments of a surface-doped graphene-like structure, composed of eight distinct atoms are studied, taking spin quantum number and temperature into account. The results show that the model has a total of eight spin wave spectra and three energy gaps and We note that the magnetic moments intersect at low temperatures, which can be attributed to quantum fluctuations. Therefore, we explore the influence of different magnetic parameters on quantum fluctuations within a three-layer model. The result shows that, in comparison to interlayer exchange coupling, intra-layer exchange coupling has a more pronounced influence on the quantum fluctuation within the three-layer model. Magnetocrystalline anisotropy of different acting forms has opposite effects on quantum fluctuation, The magnetocrystalline anisotropy inside the antiferromagnetic layer has the most obvious effect on the quantum fluctuation of the model. The quantum fluctuation values of the two sublattices in the ferromagnetosphere differ very little. [ABSTRACT FROM AUTHOR]

We report our numerical studies on the emergence of a double-Q checkerboard bubble crystal in centrosymmetric tetragonal magnets. The double-Q checkerboard bubble crystal is characterized by a fourfold-symmetric collinear spin configuration consisting of a superposition of two sinusoidal waves with the out-of-plane spin modulations along the [110] and [ 1 ¯ 10] directions. The numerical calculations based on the simulated annealing for an effective spin model with the momentum-resolved easy-axis exchange interactions reveal that the double-Q checkerboard bubble crystal is energetically degenerate with the single-Q collinear state when the ordering wave vector lies on the quarter of the reciprocal lattice vector along the 〈 110 〉 direction. We show that such a degeneracy is lifted by considering the biquadratic interaction. We also find that the double-Q checkerboard bubble crystal turns into another double-Q state characterized by the in-plane spin modulations by increasing an external magnetic field. [ABSTRACT FROM AUTHOR]

Electric currents passing through ferromagnets can impact the magnetization dynamics via the so-called spin-transfer torque (STT) effect. In this paper, we present a theoretical study on the current influence on magnonic activity, a recently reported spin wave (SW) chiral effect in ferromagnetic nanotubes. By micromagnetic simulations, we show that an electric current can cause a significant change in the rotatory power of the SW modes propagating in a longitudinally magnetized nanotube. This result is well explained by using the Fresnel model in optics assuming a SW circular birefringence. An analytical method is developed to solve the first-order mode, yielding perfect agreements with the numerical results. Our results provide a new approach to manipulate the SW propagating properties in ferromagnetic nanocylinders. [ABSTRACT FROM AUTHOR]

We investigate the instability toward a double-Q state, which consists of a superposition of two spin density waves at different wave vectors, on a two-dimensional noncentrosymmetric square lattice in an in-plane external magnetic field. By performing the simulated annealing for the spin model with the Dzyaloshinskii–Moriya interaction and bond-dependent anisotropic interaction, we obtain four types of double-Q states depending on the sign of the bond-dependent anisotropic interaction. On the other hand, only the single-Q spiral state appears in the absence of the bond-dependent anisotropic interaction. The present results suggest that the interplay between the Dzyaloshinskii–Moriya interaction and bond-dependent anisotropic interaction can give rise to multiple-Q states for both zero and nonzero in-plane magnetic fields. [ABSTRACT FROM AUTHOR]

Integration of compact, tunable, low-cost monolithic microwave integrated circuit-based bandpass filters on a semiconductor substrate has been a persistent requirement in the communication industry. In the present investigation, a compact reconfigurable bandpass filter is fabricated using a double T-transducer based on the phenomena of magnetostatic surface spin waves (MSSWs). The Ce-doped Bi0.1YIG 500 μm thick disks with cerium concentration in the range of 0.2–1.0 provide the path for the propagation of MSSWs. The operating frequency for this device extends from S to X band Rogers RT/duroid® substrate, which is used for planar microstrip filter design, fabrication, and testing for practical applications. The effect of the coupling gap between the two transducers was optimized using appropriate choice of lumped components to improve the performance of the filter. The best coupling was observed for 1.2 mm coupling gap. The simulated and experimental results confirm the lowest insertion loss of −1.24 dB. The operating frequency shows a large tunability of 132.3% with a relatively small bias field of 0.3–2.1 kOe. The promising characteristics of bandpass filters such as low passband insertion loss, narrow bandwidth, high bandpass reflection coefficient, and high band-stop rejection were achieved by varying the Ce concentration in YIG samples. [ABSTRACT FROM AUTHOR]

Surface acoustic waves (SAWs) can transmit magnetization oscillation inside magnetoelastic films in the form of magnetoacoustic waves. If the frequency and wavenumber of SAWs match those of spin waves, magnon excitation can be observed. In this work, we studied the phonon–magnon conversion excited by longitudinal leaky SAWs, which possess the same dominant strain component like Rayleigh-type SAWs but a much higher phase velocity. The measured transmission power absorptions of both SAW modes due to spin wave resonance follow a linear frequency dependence and exhibit a fourfold symmetry. We demonstrate that longitudinal leaky SAWs can serve as a very effective means to excite stronger phonon–magnon coupling than Rayleigh SAWs at a lower wave number. [ABSTRACT FROM AUTHOR]

Spin wave computing device where an algorithm can be encoded by recording a corresponding magnetization pattern onto a hard magnetic material was previously proposed [K. Rivkin and M. Montemorra, "Spin wave computing using pre-recorded magnetization patterns," J. Appl. Phys. 132, 153902–153911 (2022)] and a particular implementation of a vector-matrix algorithm was demonstrated. In the present article, we analyze the conditions allowing for implementation of complex algorithms which can combine multiple additive, multiplicative, and conditional operators including logic expressions. Special attention is given to how the input data are provided. Rather than relying on a set of independent sources of the RF field, as is common with the existing spin wave computing methods, we demonstrate usability of more simple solutions using adjustable external quasistatic magnetic fields. We also show how, for the given setup, probabilistic switching of magnetic elements at elevated temperatures can be used to convert deterministic algorithms into a probabilistic form. [ABSTRACT FROM AUTHOR]

Abstract One of the most intriguing properties of magnonic systems is their reconfigurability, where an external magnetic field alters the static magnetic configuration to influence magnetization dynamics. In this paper, we present an alternative approach to tunable magnonic systems. We studied theoretically and numerically a magnonic crystal induced within a uniform magnetic layer by a periodic magnetic field pattern created by the sequence of superconducting strips. We showed that the spin-wave spectrum can be tuned by the inhomogeneous stray field of the superconductor in response to a small uniform external magnetic field. Additionally, we demonstrated that modifying the width of superconducting strips and separation between them leads to the changes in the internal field which are unprecedented in conventional magnonic structures. The paper presents the results of semi-analytical calculations for realistic structures, which are verified by finite-element method computations.

Density wave (DW) order is believed to be correlated with superconductivity in the recently discovered high-temperature superconductor La3Ni2O7. However, experimental investigations of its evolution under high pressure are still lacking. Here, we explore the quasiparticle dynamics in bilayer nickelate La3Ni2O7 single crystals using ultrafast optical pump-probe spectroscopy under high pressures up to 34.2 GPa. At ambient pressure, the temperature-dependent relaxation dynamics demonstrate a phonon bottleneck effect due to the opening of an energy gap around 151 K. The energy scale of the DW-like gap is determined to be 66 meV by the Rothwarf-Taylor model. Combined with recent experiential results, we propose that this DW-like transition at ambient pressure and low temperature is spin density wave (SDW). With increasing pressure, this SDW order is significantly suppressed up to 13.3 GPa before it completely disappears around 26 GPa. Remarkably, at pressures above 29.4 GPa, we observe the emergence of another DW-like order with a transition temperature of approximately 135 K, which is probably related to the predicted charge density wave (CDW) order. Our study provides the experimental evidences of the evolution of the DW-like gap under high pressure, offering critical insights into the correlation between DW order and superconductivity in La3Ni2O7. The evolution of density-wave-like orders under pressure is crucial for unraveling the mechanism of superconductivity in La3Ni2O7. Here, the authors provide evidence that the spin density wave is suppressed when the superconductivity emerges, and that another density wave appears above 29 GPa. [ABSTRACT FROM AUTHOR]

This study investigates the propagation characteristics of spin waves in an yttrium iron garnet waveguide using a vector network analyzer and a real-time oscilloscope. We confirm the propagation of backward volume magnetostatic spin waves in the linear regime. Solitary spin-wave formation was observed, and the transition from linear to nonlinear response was verified by establishing a threshold power. In the nonlinear regime, collision experiments between two spin waves were conducted, revealing a dependence of attenuation on the input carrier frequency. A comparison with the transmission loss curve confirms the correlation between attenuation and the position of "frequency regions with strong dispersion." Notably, only within a specific frequency range among these regions do the colliding spin waves maintain their shapes and momenta, passing through each other without dissipation. This remarkable phenomenon is crucial for dissipation-free information transfer. Our findings offer valuable insights into spin-wave behavior, particularly for developing spin-wave-based logic and long-distance magnonic soliton information transfer. [ABSTRACT FROM AUTHOR]

A theory is presented for calculating the spin wave response of a three-dimensional damped magnetic system to an external excitation, in the frequency domain. The equation of motion, written in the Hamiltonian formalism, is discretized within a finite-element method, and the corresponding large system of equations is first linearized and then solved with well-established techniques of linear algebra, leading directly to the spectral response. This approach is therefore particularly suitable for interpreting the results of all-electric microwave measurements of magnonic crystals. The response of a three-dimensional structure, composed of a portion of a square array of circular dots placed in close proximity of a magnetic substrate, is then investigated. A prominent, narrow feature with a large rejection ratio is observed in the spin wave transmission spectrum, making this structure useful as a narrowband notch filter. [ABSTRACT FROM AUTHOR]

The effect of the variation of the spin current on the magnetic susceptibility of a magnonic waveguide in the form of a "ferromagnet–normal metal" heterostructure is investigated. Based on the Landau–Lifshitz–Gilbert model with the current term in the Slonczewski–Berger form, which describes the magnetization dynamics including the spin moment transfer, expressions are obtained for the real and imaginary parts of the magnetic susceptibility in the geometry of surface spin waves in the damping mode. The resulting model correctly approximates experimental data demonstrating an increase in the amplitude of spin waves propagating in a YIG/Pt heterostructure. It is shown that an increase in the spin current leads to an increase in the resonance frequency of spin waves and in the magnetic susceptibility tensor components in resonance. The results of this study can be used to design waveguides for spin waves with controllable losses and high-sensitivity magnetic field sensors. [ABSTRACT FROM AUTHOR]

In this study, we suggest a method to amplify spin waves (SWs) in antiferromagnets (AFMs). By introducing a non-uniform Dzyaloshinskii–Moriya (DM) interaction, the potential barrier forms a resonant cavity. SWs with an opposite chirality undergo scattering and are resonantly amplified at a phase-matching condition. The calculation is performed in the insulating AFMs where the electric-field-induced DM interaction and pseudo-dipole anisotropy broaden the parabolic-like SW band for multiple resonant modes. Using a transfer matrix method, we also show numerically that scattering between SWs contributes significantly to the SW amplification. Since the electric field selectively amplifies the SWs with resonant frequencies, the proposed device works as an SW transistor and rectifier. This finding will contribute to insulating AFM-based magnon devices where Joule heating is, in principle, avoided. [ABSTRACT FROM AUTHOR]

Large-scale inter-combustor thermoacoustic interactions occur frequently in modern can-annular gas turbine combustion systems due to the presence of an annular cross-talk section upstream of the first stage turbine stator vanes. Although the whole system's modal dynamics depend on the relative dominance of low-frequency planar or high-frequency transverse acoustic waves, the majority of prior studies have chiefly focused on longitudinal mode instabilities. Motivated by the paucity of detailed information, here we examine high-frequency transverse acoustic interactions between two adjacent lean-premixed hydrogen combustors connected via two different pathways, known as cross-fire (XF) and cross-talk (XT) sections. We observe that the dual-combustor system undergoes high-frequency spinning mode in the clockwise direction, manifested as well-defined limit cycles with peak-to-peak amplitude of around 10 kPa. The transverse pressure oscillations, in contrast to the well-established low-frequency mutual synchronization dynamics, are not fully synchronized even in the presence of cross-talk communication. This situation leads to the formation of two closely-spaced 1T modes at 4.76 and 4.86 kHz in the respective hydrogen combustors, accompanied by the beating of the pressure fluctuations solely in the XF tube section. Remarkably, the pressure waves induced near the XF tube section tend to lag behind the pressure waves spinning in the injector face, demonstrating the existence of the angular shift characteristically connected to the high-frequency transverse combustion dynamics. • High-frequency transverse instabilities are investigated in subscale dual-combustor test environments. • Distinctive features derived from high-frequency cross-talk interactions are experimentally identified. • Collective dynamics are characterized by weak coupling-induced beating in cross-fire section. • Angular shift in spinning modes is generated from two acoustically coupled hydrogen combustors. [ABSTRACT FROM AUTHOR]

Photonic integrated quantum memories are essential for the construction of scalable quantum networks. Spin-wave quantum storage, which can support on-demand retrieval with a long lifetime, is indispensable for practical applications, but has never been demonstrated in an integrated solid-state device. Here, we demonstrate spin-wave quantum storage based on a laser-written waveguide fabricated in a 151Eu3+:Y2SiO5 crystal, using both the atomic frequency comb and noiseless photon-echo protocols. Qubits encoded with single-photon-level inputs are stored and retrieved with a fidelity of |${94.9\%\pm 1.2\%}$|⁠ , which is far beyond the maximal fidelity that can be obtained with any classical device. Our results underline the potential of laser-written integrated devices for practical applications in large-scale quantum networks, such as the construction of multiplexed quantum repeaters in an integrated configuration and high-density transportable quantum memories. [ABSTRACT FROM AUTHOR]

We theoretically studied the dynamic properties of the skyrmion driven by electromagnetic (EM) waves with spin angular momentum (SAM) and orbital angular momentum (OAM) using micromagnetic simulations. First, the guiding centers of the skyrmion driven by EM waves with SAM, i.e., left-handed and right-handed circularly polarized EM waves, present circular trajectories, while present elliptical trajectories under linear EM waves driving due to the superposition of oppositely polarized wave components. Second, the trajectories of the skyrmion driven by EM waves with OAM demonstrate similar behavior to that driven by linearly polarized EM waves. Because the wave vector intensity varies with the phase for both linearly polarized EM waves and EM waves with OAM, the angular momentum is transferred to the skyrmion non-uniformly, while the angular momentum is transferred to the skyrmion uniformly for left-handed and right-handed circularly polarized EM driving. Third, the dynamic properties of the skyrmion driven by EM waves with both SAM and OAM are investigated. It is found that the dynamic trajectories exhibit more complex behavior due to the contributions or competition of SAM and OAM. We investigate the characteristics of intrinsic gyration modes and frequency-dependent trajectories. Our research may provide insight into the dynamic properties of skyrmion manipulated by EM waves with SAM or OAM and provide a method for controlling skyrmion in spintronic devices. [ABSTRACT FROM AUTHOR]

We study the magnon spectrum in a thin ferromagnet–superconductor heterostructure in the presence of a single superconducting vortex. We employ the Bogolubov–de Gennes Hamiltonian which describes the magnons in the presence of the stray magnetic field and the nonuniform magnetic texture induced by the vortex. We find that the vortex localizes magnon states approximately in the same way as a charge center produces electron bound states due to screened Coulomb interaction in the two-dimensional electron gas. The number of these localized states is substantially determined by the material parameters of the ferromagnetic film only. We solve the scattering problem for an incident plane spin wave and compute the total and transport cross sections. We demonstrate that the vortex-induced nonuniform magnetic texture in chiral ferromagnetic film produces a skew scattering of magnons. We explore the peculiarities of the quantum scattering problem that correspond to orbiting in the classical limit. [ABSTRACT FROM AUTHOR]

Non-coplanar spin textures such as magnetic vortices and skyrmions manifest themselves in unusual physical phenomena owing to their topologically nontrivial properties. Here, we investigate emergent multipole moments under vortex and skyrmion crystals in the centrosymmetric tetragonal system. Depending on the vorticity and helicity of the vortex or skyrmion, various multipole moments, including magnetic toroidal and electric toroidal multipoles, are induced on the atomic scale. In particular, the vortex and skyrmion spin textures consisting of multiple spin density waves give rise to density waves in terms of other multipole moments. Our results reveal a close relationship between non-coplanar multiple-Q spin textures and multipole moments. [ABSTRACT FROM AUTHOR]

To control the spin wave (SW) propagation, external energy sources such as magnetic fields, electric currents, or complex nanopatterning are used, which can be challenging at the deep nanoscale level. In this work, we overcome such limitations by demonstrating SW propagation in Pt/Co multilayers at a remanent state controlled by stripe domain patterns, using Brillouin light scattering and micromagnetic simulations. We show that parallel stripes with a periodicity around 100 nm exhibit reconfigurability, as the stripes can be rotated by applying the in-plane field without damaging their shape. This allows us to study SW propagation perpendicular and parallel to the stripes. We observe multimodal SW spectra—three bands in perpendicular and five in parallel geometry. Numerical results allow us to identify all observed modes and to explain the differences between two configurations by the unequal contribution of all three magnetization components in the SW dynamics. We find that the experimentally measured non-reciprocal dispersion (for the wavevector perpendicular to the stripes) is not the breaking of time-symmetry but the asymmetry in intensity of the measured signals of two different low-frequency modes, which is due to the inhomogeneous SW amplitude distribution over the multilayer thickness and the limited light penetration depth. Our results pave the way for easy reprogrammability and high energy efficiency in nanomagnonics. [ABSTRACT FROM AUTHOR]