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This work theoretically analyzes electronic ordering in AA-stacked bilayer graphene and the role of the Coulomb interaction in these many-body phenomena. Using the random phase approximation to account for screening, we find intra-layer effective interactions to be much stronger than inter-layer interactions; under certain circumstances, the latter may also become attractive. At zero doping, the Coulomb repulsion stabilizes the spin-density wave state, with a Néel temperature in the tens of Kelvin. While dominant in the undoped system, the spin-density wave is destroyed by sufficiently strong doping and a superconducting phase emerges. We find that the effective Coulomb inter-layer interaction can give rise to superconductivity. However, the corresponding critical temperature is negligibly small, and phonon-mediated attraction must be introduced to observe it. Strong intra-layer repulsion suppresses order parameters that couple two intra-layer electrons. We point out a possible superconducting state with finite Cooper pair momentum. • The RPA Coulomb interaction between electrons localized in different layers of AA-stacked graphene bilayer is significantly weakened by screening. • It is argued that at zero doping the system enters the spin-density wave phase, with the ordering temperature of several tens of kelvin. • At finite doping, the superconducting phase become possible. • The superconductivity is the result of the interplay between the Coulomb interaction and phonon-mediated attraction. [ABSTRACT FROM AUTHOR]

Two-dimensional ferromagnetic nanodot structures exhibit intriguing magnetization dynamics and hold promise for future magnonic devices. In this study, we present a comparative experimental investigation into the reconfigurable magnetization dynamics of non-ellipsoidal diamond and triangular-shaped nanodot structures, employing broadband ferromagnetic resonance spectroscopy. Our findings reveal substantial variations in the spin wave (SW) spectra of these structures under different bias field strengths (H) and angles (φ). Notably, the diamond nanodot structure exhibits a variation from nearly symmetric W-shaped dispersion to a skewed dispersion and subsequent transition to a discontinuous dispersion with subtle variation in bias field angle. On the other hand, in the triangular nanodot array a SW mode anti-crossing appears at φ = 15° which is starkly modified with the increase in φ to 30°. By analyzing the static magnetic configurations, we unveil the nature of the SW spectra in these two shapes. We reinforce our observations with simulated spatial power and phase maps. This study underscores the critical impact of dot shape and inversion symmetry on SW dynamical response, highlighting the significance of selecting appropriate structures and bias field strength and orientation for required functionalities. The remarkable tunability demonstrated by the magnonic crystals underscores their potential suitability for future magnonic devices. • Bias-field engineering of spin wave dynamics in diamond and triangular-shaped nanodot arrays arranged in square lattice. • Reconfigurability of spin wave spectra and mode softening phenomena in diamond-shaped nanodot array. • Mode hybridization due to magnon-magnon coupling in triangular-shaped nanodot array and its reconfigurability. [ABSTRACT FROM AUTHOR]

The paper reports on the principle of signals demultiplexing in the structure ferromagnetic film/normal metal/magnonic crystal. It is discovered that in such a structure there is a formation of four band gaps — spin wave forbidden bands. It is shown that depending on the frequency, the signal comes out through different ports of the structure (ferromagnetic film or magnonic crystal), i.e. there is frequency division of channels. The influence of spin current on the signal coupling at frequencies inside the band gap significantly prevails over the effect of spin current at frequencies outside the band gap. The spin current allows effective control of the main line insertion loss of a directional coupler based on such a structure. The spin current has little effect on coupling factor and isolation. [ABSTRACT FROM AUTHOR]

The exact expression of the wave vector inside a spinning homogeneous dielectric sphere illuminated by polarized plane waves is derived utilizing the "instantaneous rest-frame" hypothesis and Minkowski's theory. On this basis, the analytical expressions of the electromagnetic field in the rotation sphere system are attained. The asymmetry of the system is discussed, in which the cause is emphasized. The influence of the polarization states and rotation angular velocity on the scattering are analyzed, including the optical rotation effect and photonic hook (PH). The results of this manuscript have extensive application prospects in optical tweezers, particle manipulation, and antenna design. • The scattering of rotating dielectric spheres to polarized plane waves with different transmission directions is discussed. • The asymmetry of the scattered field induced by rotation is analyzed, and the reasons are explored. • The effect of the polarization states of the incident plane wave on the asymmetry of the rotation system is highlighted. • The optical rotation effect and photonic hook (PH) generated by rotation are discussed. [ABSTRACT FROM AUTHOR]

The article "De-noising of EEG signals with shift-based cycle spinning on wave atoms" has been retracted by the publisher due to concerns about compromised editorial handling and peer review processes, inappropriate references, and being out of scope for the journal. The investigation found multiple articles, including this one, with similar issues, leading to a loss of confidence in the results and conclusions. The authors have not responded to inquiries about the retraction. [Extracted from the article]

Nonreciprocity, unidirectionality, and channeling are essential concepts for potential magnonic applications. Nonreciprocity and unidirectionality ensure the efficient propagation of spin waves along predetermined paths with preferential directions, disrupting the symmetry of counterpropagating waves. Channeling fosters the development of intricate spin-wave networks, enabling more sophisticated functionalities. Integrating these concepts into practical applications will shape the future of spin-wave-based information processing devices. This article theoretically studies the dynamics of spin waves in a ferromagnetic strip coupled to a heavy-metal strip, where the nonreciprocity, unidirectionality, and channeling effects are analyzed. Both backward volume (BV) and Damon–Eshbach (DE) configurations are considered, where the lateral dimensions of the heavy-metal and ferromagnetic strips can differ. Calculations show notable nonreciprocal channeling of spin waves in both DE and BV modes. In the BV configuration, the dispersion is reciprocal with nontrivial localization of lateral confined modes. It is shown that the waves can be channeled into the zones in contact with the HM, where the Dzyaloshinskii–Moriya interaction is active. In the DE configuration, the waves exhibit nonreciprocal spin-wave dispersion, allowing unidirectional and channeled spin-wave propagation. The main results are compared to micromagnetic simulations, where an excellent agreement between both methods is obtained. These findings are relevant for envisioning advanced magnonic devices, enabling precise control over spin-wave propagation for innovative, low-power, high-speed information processing. • The work presents a novel nanometric system that can serve to channel the spin waves. • Spin-wave channeling is observed for backward volume and Damon–Eshbach configurations. • Nonreciprocal spin-wave channeling is obtained, which can be useful for designing advanced magnonic devices, like magnonic diodes. [ABSTRACT FROM AUTHOR]

Magnonic crystals are metamaterials whose magnon behavior can be controlled for specific applications. To date, most magnonic crystals have relied on nanopatterning and magnetostatic waves. Here, we analytically and numerically investigate magnonic crystals defined by modulating magnetic parameters at the nanoscale, which predominantly act on exchange-dominated, sub-100 nm magnons. We focus on two cases: the variation in the exchange constant, and the DMI constant. We found that the exchange constant modulation gives rise to modest band gaps in the forward volume wave and surface wave configurations. The modulation of the DMI constant was found to have little effect on the magnonic band structure, leading instead to a behavior expected for unpatterned thin films. We believe that our results will be interesting for future experimental investigations of nano-designed magnonic crystals and magnonic devices, where material parameters can be locally controlled, e.g., by thermal nano-lithography.

The low-energy excitation spectrum of a two-dimensional ferromagnetic material is dominated by single-magnon excitations that show a gapless parabolic dispersion relation with the spin wave vector. This occurs as long as magnetic anisotropy and anisotropic exchange are negligible compared to isotropic exchange. However, to maintain magnetic order at finite temperatures in extended systems, it is necessary to have sizable anisotropy to open a gap in the spin wave excitation spectrum. We consider four real two-dimensional systems for which ferromagnetic order at finite temperature has been observed or predicted. Density functional theory calculations of the total energy differences for different spin configurations permit us to extract the relevant parameters and connect them with a spin Hamiltonian. The corresponding values of the Curie temperature are estimated using a simple model and found to be mostly determined by the value of the isotropic exchange. The exchange and anisotropy parameters are used in a toy model of finite-size periodic chains to study the low-energy excitation spectrum, including single-magnon and two-magnon excitations. At low energies, we find that single-magnon excitations appear in the spectrum together with two-magnon excitations. These excitations present a gap that grows particularly for large values of the magnetic anisotropy or anisotropic exchange, relative to the isotropic exchange.

We report experiments which characterize spin wave propagation in a thin (111) yttrium iron garnet film for arbitrary angles between the in-plane magnetic field and the mode wavevectors. By measuring the magnetic field evolution of the phase of the wave traveling across the film, we deduce the frequency dependence of the wavevector, the dispersion relation, from which the mode velocity follows. Additionally, we observe multiple nodes in the regime of the propagating Damon-Eshbach mode; these arise from avoided crossings associated with the higher, exchange split, standing wave modes along the film normal, the positions of which correlate with the direct absorption measurements of their positions. This information allows a determination of the exchange parameter. Using this technique, we examine the nonreciprocity in spin wave propagation that results from an adjacent metal layer. [ABSTRACT FROM AUTHOR]

The physical origin of the magnetoplastic effect was experimentally identified in Al polycrystalline alloy. Exposure of the nominally pure industrial Al-Mg-Si-Fe alloy to magnetic field 0.7 T induces residual changes that provide a creep rate increase up to 25% and microhardness decrease down to 30%. FeAl inclusions of ∼1 μm size were revealed in the alloy. Magnetostriction of the ferromagnetic inclusions providing local mechanical stresses and generation of fresh dislocations in the vicinity of the inclusions is the main reason for magnetoplasticity. Ferro-, antiferro-, and paramagnetic contributions of the inclusions and/or Fe atoms distributed in the Al matrix have been distinguished. The chemical composition of FeAl inclusions determined by transition electron microscopy and local field probed by the Mossbauer technique are in good agreement with saturation magnetization of the FeAl alloys. [ABSTRACT FROM AUTHOR]

Electromagnons (Electroactive spin wave excitations) could prove to be decisive in information technologies but they remain fragile quantum objects, mainly existing at low temperatures. Any future technological application requires overcoming these two limitations. By means of synchrotron radiation infrared spectroscopy performed in the THz energy range and under hydrostatic pressure, we tracked the electromagnon in the cupric oxide CuO, despite its very low absorption intensity. We demonstrate how a low pressure of 3.3 GPa strongly increases the strength of the electromagnon and expands its existence to a large temperature range enhanced by 40 K. Accordingly, these two combined effects make the electromagnon of CuO under pressure a more ductile quantum object. Numerical simulations based on an extended Heisenberg model were combined to the Monte-Carlo technique and spin dynamics to account for the magnetic phase diagram of CuO. They enable to simulate the absorbance response of the CuO electromagnons in the THz range. [ABSTRACT FROM AUTHOR]

The dispersion relationships in antiferromagnetically coupled magnonic crystals (MCs) were investigated using micromagnetic simulations. In contrast to traditional MCs, antiferromagnetically coupled MCs have two oppositely polarized modes, enabling the realization of synthetic ferrimagnetic and synthetic antiferromagnetic MCs. The magnon flatband effect was discovered, and a large bandgap of the dispersion relation was also realized in this structure. We found that the center frequency and width of the dispersion bands with a specific polarization were influenced by the thickness and thickness ratio of the spin-up and spin-down magnetic sublattices. Based on these results, spin-wave filtering devices were proposed. Our study uncovered the magnon dispersion relations of a type of MC, which provides fresh insights into the development of ultra-efficient magnonic devices. [ABSTRACT FROM AUTHOR]

Spin-pumping-induced damping and interfacial Dzyaloshinskii–Moriya interaction (iDMI) have been studied in Pt/Co2FeAl/MgO systems grown on Si or MgO substrates as a function of Pt and Co2FeAl (CFA) thicknesses. For this, we combined vibrating sample magnetometry (VSM), microstrip ferromagnetic resonance (MS-FMR), and Brillouin light scattering (BLS). VSM measurements of the magnetic moment at saturation per unit area revealed the absence of a magnetic dead layer in both systems, with a higher magnetization at saturation obtained for CFA grown on MgO. The key parameters governing the spin-dependent transport through the Pt/CFA interface, including the spin mixing conductance and the spin diffusion length, have been determined from the CFA and the Pt thickness dependence of the damping. BLS has been used to measure the spin wave non-reciprocity via the frequency mismatch between the Stokes and anti-Stokes lines. iDMI has been separated from the contribution of the interface perpendicular anisotropy difference between Pt/CFA and CFA/MgO. Our investigation revealed that both iDMI strength and spin pumping efficiency are higher for CFA-based systems grown on MgO due to its epitaxial growth confirmed by MS-FMR measurements of the in-plane magnetic anisotropy. This suggests that CFA grown on MgO could be a promising material candidate as a spin injection source via spin pumping and for other spintronic applications. [ABSTRACT FROM AUTHOR]

Nonlinear magnetic resonance is studied in an in-plane magnetized yttrium iron garnet (YIG) film. For YIG films magnetized perpendicular to the plane, the effect referred to as the foldover resonance is well known. It arises because the precession frequency increases with the deviation of the magnetization. When the field is reduced, the frequency of the precession remains resonant because the demagnetizing field decreases with the deviation of the magnetization. The signal disappears when the radio frequency pump power is insufficient to maintain a nonequilibrium state of the system. In the in-plane magnetized yttrium iron garnet film, the precession frequency decreases with an increase in the pump amplitude. Accordingly, the foldover effect arises under an increase in the field. The fundamental difference is that the precession in the latter case should be unstable with respect to the decay into spin wave modes. The deviation angles of magnetization of about 10° are reached, and the rate of decay of the uniform precession into spin waves, which depends on the deviation angle of the magnetization, is measured. This study opens up another way of achieving the magnon density corresponding to the formation of its Bose–Einstein condensate. [ABSTRACT FROM AUTHOR]

The article presents a neural network based on magnon scattering modulated by an omnidirectional mobile hopfion in antiferromagnets, including the connections between neurons are related to the frequency dependence of magnon scattering, which allows for high connection density and meta-learning. It also mentions that the proposed design could break the connection density bottleneck in neuromorphic computing and provide a guideline for future design.

Superconductivity in the cuprates is found to be intertwined with charge and spin density waves. Determining the interactions between the different types of order is crucial for understanding these important materials. Here, we elucidate the role of the charge density wave (CDW) in the prototypical cuprate La1.885Sr0.115CuO4, by studying the effects of large magnetic fields (H) up to 24 Tesla. At low temperatures (T), the observed CDW peaks reveal two distinct regions in the material: a majority phase with short-range CDW coexisting with superconductivity, and a minority phase with longer-range CDW coexisting with static spin density wave (SDW). With increasing magnetic field, the CDW first grows smoothly in a manner similar to the SDW. However, at high fields we discover a sudden increase in the CDW amplitude upon entering the vortex-liquid state. Our results signify strong coupling of the CDW to mobile superconducting vortices and link enhanced CDW amplitude with local superconducting pairing across the H − T phase diagram. Superconductivity in the cuprates is known to be intertwined with charge and spin density waves. Here, the authors study the prototypical cuprate La1.885Sr0.115CuO4 via x-ray scattering and discover a sudden increase in the charge-density-wave amplitude upon entering the superconducting-vortex-liquid state at high magnetic field. [ABSTRACT FROM AUTHOR]

A significant activity is devoted to the investigation of the ultrafast spin dynamic processes, holding a great potential for science and applications. However, a challenge of the understanding of the mechanisms of underlying spin dynamics in nanomaterials at pico- and femtosecond timescales remains under discussion. In this article, we explore the gyrotropic vortex dynamics in a circular soft magnetic nanodot, highlighting the impacts given by nutations in the high-frequency part of the dot spin excitation spectrum. Using a modified Thiele equation of the vortex core motion with a nutation term, we analyze the dynamic response of the vortex to an oscillating magnetic field applied in the dot plane. It is found that nutations affect the trajectory of the vortex core. Namely, we show that the directions of the vortex core motion in the low-frequency gyrotropic mode and the high-frequency nutation mode are opposite. The resonant frequencies of gyrotropic and nutational vortex core motions reveal themselves on different scales: gigahertz for the gyrotropic motion and terahertz for the nutations. We argue that the nutations induce a dynamic vortex mass, present estimates of the nutational mass, and conduct comparison with the mass appearing due to moving vortex interactions with spin waves and Doering domain wall mass. [ABSTRACT FROM AUTHOR]

Mercury's peculiar orbit around the Sun (3:2 spin–orbit resonance) and lack of atmosphere result in one the widest temperature ranges experienced at the surface of a planetary body in the solar system. Temperature variations affect the physical and, therefore, spectral properties of minerals to varying degrees; thus, it is crucial to study them in the context of the upcoming arrival of the BepiColombo spacecraft in Mercury orbit in the fall of 2025. In this work, we heated and cooled analog materials (plagioclase and volcanic glasses) at temperatures representative of the hermean surface. With our experimental setup, we could measure near-infrared (1.0–3.5 μ m) and thermal infrared (2.0–14.3 μ m) reflectance spectra of our analogs at various temperatures during a heating (25–400 ∘ C) or cooling cycle (−125–25 ∘ C), allowing us to follow the evolution of the spectral properties of minerals. We also collected reflectance spectra in the visible domain (0.47–14.3 μ m) before and after heating. In the visible spectra, we identified irreversible changes in the spectral slope (reddening) and the reflectance (darkening or brightening) that are possibly associated with oxidation, whereas the temperature had reversible effects (e.g., band shifts of from ten to a hundred nanometers towards greater wavelengths) on the infrared spectral features of our samples. These reversible changes are likely caused by the crystal lattice dilatation during heating. Finally, we took advantage of the water and ice present on/in our samples to study the different components of the absorption band at 3.0 μ m when varying temperatures, which may be useful as a complement to future observations of the north pole of Mercury. The wavelength ranges covered by our measurements are of interest for the SIMBIO-SYS and MERTIS instruments, which will map the mineralogy of Mercury's surface from spring 2026, and for which we selected useful spectral parameters that are proxies of surface temperature variations. [ABSTRACT FROM AUTHOR]

This work studies the magnetic excitations of amorphous ferromagnetic alloys (Fe40Ni40P1411B6 and Fe48Ni34P18) by small‐angle polarized neutron scattering in the geometry when the magnetic field is inclined towards the neutron beam direction. Polarized neutrons are used in order to extract the scattering arising from the spin waves only. In this case, the energy‐integrated neutron cross section contains a component which depends on neutron polarization and has a left–right asymmetry in the plane determined by the directions of the field and the neutron beam. Small‐angle polarized neutron scattering measurements on spin waves in amorphous iron–nickel alloys were performed at different values of the external magnetic field H and neutron wavelength λ. The spin‐wave spectrum is quadratic in terms of the momentum transfer and contains both a field gap and an inherent gap Δ of a non‐field nature: Eq = Aq2 + gμBH + Δ. Only by measuring simultaneously two dependencies of the cut‐off angle θc – on the applied magnetic field and on the neutron wavelength – is it possible to obtain reliable information about the spin‐wave stiffness and the spin‐wave gap in these amorphous ferromagnetic systems. [ABSTRACT FROM AUTHOR]

Brillouin light scattering (BLS) has been established as a standard technique to study thermally excited sound waves with frequencies up to ~100 GHz in transparent materials. In BLS experiments, one usually uses a Fabry–Pérot interferometer (FPI) as a spectrometer. The drastic improvement of the FPI contrast factor over 1010 by the development of the multipass type and the tandem multipass type FPIs opened a gateway to investigate low energy excitations (ħω ≤ 1 meV) in various research fields of condensed matter physics, including surface acoustic waves and spin waves from opaque surfaces. Over the last four decades, the BLS technique has been successfully applied to study collective spin waves (SWs) in various types of magnetic structures including thin films, ultrathin films, multilayers, superlattices, and artificially arranged dots and wires using high-contrast FPIs. Now, the BLS technique has been fully established as a unique and powerful technique not only for determination of the basic magnetic constants, including the gyromagnetic ratio, the magnetic anisotropy constants, the magnetization, the SW stiffness constant, and other features of various magnetic materials and structures, but also for investigations into coupling phenomena and surface and interface phenomena in artificial magnetic structures. BLS investigations on the Fe/Cr multilayers, which exhibit ferromagnetic-antiferromagnetic arrangements of the adjacent Fe layer's magnetizations depending on the Cr layer's thickness, played an important role to open the new field known as "spintronics" through the discovery of the giant magnetoresistance (GMR) effect. In this review, I briefly surveyed the historical development of SW studies using the BLS technique and theoretical background, and I concentrated our BLS SW studies performed at Tohoku University and Ishinomaki Senshu University over the last thirty five years. In addition to the ferromagnetic SW studies, the BLS technique can be also applied to investigations of high-frequency magnetization dynamics in superparamagnetic (SPM) nanogranular films in the frequency domain above 10 GHz. One can excite dipole-coupled SPM excitations under external magnetic fields and observe them via the BLS technique. The external field strength determines the SPM excitations' frequencies. By performing a numerical analysis of the BLS spectrum as a function of the external magnetic field and temperature, one can investigate the high-frequency magnetization dynamics in the SPM state and determine the magnetization relaxation parameters. [ABSTRACT FROM AUTHOR]

The interplay of the staggered and the three‐body interaction potentials on the quantum phases of a spin‐1 Bose Hubbard model using a mean field approximation (MFA) is studied. In the antiferromagnetic (AF) case, a smaller value of the staggered potential (SP) results in the charge and the spin density wave ordering along with the Mott insulator (MI) and the staggered superfluid (SSF) phases. While the competition between two types of the potential leads to the stabilization of the higher order MI and charge density wave (CDW) phases with increasing three‐body interaction strength. Further, the spin eigenvalue and nematic order parameters are calculated to scrutinize the spin singlet‐nematic formation in the MI and the CDW phases and spin population fractions to analyze the nature of the SSF phase. A signature of the spin density wave (SDW) pattern is also observed in the gapped phase lobes. In case of a purely three‐body interaction, the third and higher order insulating lobes become dominant with increasing staggered potential strength. Subsequently, all MFA phase diagrams are then nicely corroborated with the analytical results obtained using a perturbative expansion corresponding to the AF and ferromagnetic cases. [ABSTRACT FROM AUTHOR]

Magnonic holographic memory is a type of memory that uses spin waves for magnetic bit read-in and read-out. Its operation is based on the interaction between magnets and propagating spin waves where the phase and the amplitude of the spin wave are sensitive to the magnetic field produced by the magnet. Memory states 0 and 1 are associated with the presence/absence of the magnet in a specific location. In this work, we present experimental data showing the feasibility of magnetic bit location using spin waves. The testbed consists of four micro-antennas covered by Y3Fe2(FeO4)3 yttrium iron garnet (YIG) film. A constant in-plane bias magnetic field is provided by NdFeB permanent magnet. The magnetic bit is made of strips of magnetic steel to maximize interaction with propagating spin waves. In the first set of experiments, the position of the bit was concluded by the change produced in the transmittance between two antennas. The minima appear at different frequencies and show different depths for different positions of the bit. In the second set of experiments, two input spin waves were generated, where the phase difference between the waves is controlled by the phase shifter. The minima in the transmitted spectra appear at different phases for different positions of magnetic bit. The utilization of the structured bit enhances its interaction with propagating spin waves and improves recognition fidelity compared to a regular-shaped bit. The recognition accuracy is further improved by exploiting spin wave interference. The depth of the transmission minima corresponding to different magnet positions may exceed 30 dB. All experiments are accomplished at room temperature. Overall, the presented data demonstrate the practical feasibility of using spin waves for magnetic bit red-out. The practical challenges are also discussed. [ABSTRACT FROM AUTHOR]

We report unidirectional transmission of micron-wide spin waves beams in a 55 nm thin YIG. We downscaled a chiral coupling technique implementing Ni80Fe20 nanowires arrays with different widths and lattice spacing to study the non-reciprocal transmission of exchange spin waves down to λ ≈ 80 nm. A full spin wave spectroscopy analysis of these high wavevector coupled-modes shows some difficulties to characterize their propagation properties, due to both the non-monotonous field dependence of the coupling efficiency, and also the inhomogeneous stray field from the nanowires. [ABSTRACT FROM AUTHOR]

The temperature dependence of the Hall coefficient, RH, for the (Cr100−xAlx)95Mo5 alloy system with 0 ≤ x ≤ 8.6, in the temperature range 2 K ≤ T ≤ 380 K and in a magnetic field of 4.5 T is reported. Anomalies in the form of an upturn were observed just below the Néel transition temperature, TN, for the incommensurate (I) spin density wave (SDW) alloys with x ≤ 1.3 and commensurate (C) spin density wave (SDW) alloys with x ≥ 5.3. In addition to these anomalies, alloys with x = 0, 0.5, 0.9 and 8.6 show a peculiar behaviour below TN, in which RH increases and then decreases depicting a hump on further cooling. Remarkably RH for the alloy with x = 0 shows a sign reversal of majority charge carriers from holes to electrons on cooling below 120 K. The crossover of majority charge carriers disappears by the addition of just 0.5 at.% Al into the base alloy with x = 0. The behaviour of the Hall coefficient for the alloys with x = 0, 0.5, 0.9 and 8.6, is explained in terms of the simple two band model in which both charge carriers contribute to magneto-transport properties. The relative magnetic contribution to the Hall coefficient, ΔRH(2K)/RH(2K), indicate a suppression of antiferromagnetism in the concentration range 1.7 ≤ x ≤ 4.7. [ABSTRACT FROM AUTHOR]

Inverse spinel oxide NiCo2O4 (NCO) is known to exhibit ferrimagnetic characteristics and electrical conductivity. First-principles calculations predict NCO to be a half-metal with a negative polarization of −100%. In this study, we fabricated epitaxial NCO/MgO/Fe magnetic tunnel junctions by reactive molecular beam epitaxy and observed an inverse tunnel magnetoresistance (TMR) effect of −19.1% at 14 K, indicating that NCO has negative spin polarization. The TMR ratio monotonically decreased with increasing temperature, which was attributed to the temperature dependence of the NCO surface magnetization due to the thermal excitation of spin waves. In addition, the TMR ratio displayed strong bias voltage dependence, decreasing to less than half of the maximum value at +20 and −30 mV. These findings support the use of NCO in spintronic devices and should lead to further developments in oxide spintronics. [ABSTRACT FROM AUTHOR]

Topological magnetic structures in ferromagnetic materials have attracted considerable attention due to their interesting physics and potential applications in devices. Ferromagnetic materials often exhibit magnetoelastic coupling effect. Therefore, topological magnetic structures can be modulated by strain engineering. In order to understand the mechanism of strain modulation and dynamic properties of topological magnetic structures, different phase field models have been proposed to predict the evolutions of topological magnetic orders. In this review, we first introduce the phase field models based on micromagnetic theory, elastodynamic equation, and Maxwell equation. Then, we review the recent progress in phase field simulations on the mechanical manipulation of the topological magnetic structures, including magnetic domain wall, vortex, and skyrmion. Based on the phase field modeling of dynamic characteristics of topological magnetic structures, the present review also discusses the modes of topological magnetic structures in frequency domain, the modulation of magnetization under different external fields, and the coupling between topological magnetic structures and spin waves. The review concludes by briefly addressing the future research directions in the field. [ABSTRACT FROM AUTHOR]

Improvement of transmission efficiency of spin waves in magnonic devices is crucial for high‐efficiency magnon‐based operations. However, existing techniques for enhancing spin‐wave detection signals, which either improve waveguide material quality or convert other forms of external energy into magnon energy, are still not efficient and convenient enough. Here, it is experimentally demonstrated that low‐k spin waves (where k is the wavenumber) transmission efficiency can be enhanced through yttrium iron garnet (YIG) surface metallization owing to the significantly increased group velocity and low spin‐pumping efficiency at low k. Given that the shielding effect of the conductive metal on YIG increases the spin‐wave group velocity from 55 to 132 km s−1, the weak magnon‐dissipation mechanism of low‐k spin waves provides the foundation for signal enhancement. Through a detailed theoretical analysis on dispersion relations and spin‐wave amplitude, the detected signal strength is increased to 2 times for copper and 2.24 times for gold is verified. In detail the competition between the spin‐pumping effect is discussed and the enhanced group velocity is introduced by the metal decoration. This competition describes the essence of partial signal enhancement in the spin‐wave transmission spectrum. The work provides a practical way to achieve spin‐wave manipulation and low‐loss transmission. [ABSTRACT FROM AUTHOR]

Texture-based magnonics focuses on the utilization of spin waves in magnetization textures to process information. Using micromagnetic simulations, we study how (1) the dynamic magnetic susceptibility, (2) dispersion relations, and (3) the equilibrium magnetic configurations in periodic magnetization textures in a ultrathin ferromagnetic film in remanence depend on the values of the Dzyaloshinskii–Moriya interaction and the perpendicular magnetocrystalline anisotropy. We observe that for large Dzyaloshinskii–Moriya interaction values, spin spirals with periods of tens of nanometers are the preferred state; for small Dzyaloshinskii–Moriya interaction values and large anisotropies, stripe domain patterns with over a thousand times larger period are preferable. We observe and explain the selectivity of the excitation of resonant modes by a linearly polarized microwave field. We study the propagation of spin waves along and perpendicular to the direction of the periodicity. For propagation along the direction of the periodicity, we observe a bandgap that closes and reopens, which is accompanied by a swap in the order of the bands. For waves propagating in the perpendicular direction, some modes can be used for unidirectional channeling of spin waves. Overall, our findings are promising in sensing and signal processing applications and explain the fundamental properties of periodic magnetization textures. [ABSTRACT FROM AUTHOR]

1D spin-wave conduits are envisioned as nanoscale components of magnonics-based logic and computing schemes for future generation electronics. À-la-carte methods of versatile control of the local magnetization dynamics in such nanochannels are highly desired for efficient steering of the spin waves in magnonic devices. Here, we present a study of localized dynamical modes in 1- μ m-wide permalloy conduits probed by microresonator ferromagnetic resonance technique. We clearly observe the lowest-energy edge mode in the microstrip after its edges were finely trimmed by means of focused Ne + ion irradiation. Furthermore, after milling the microstrip along its long axis by focused ion beams, creating consecutively ∼ 50 and ∼ 100 nm gaps, additional resonances emerge and are attributed to modes localized at the inner edges of the separated strips. To visualize the mode distribution, spatially resolved Brillouin light scattering microscopy was used showing an excellent agreement with the ferromagnetic resonance data and confirming the mode localization at the outer/inner edges of the strips depending on the magnitude of the applied magnetic field. Micromagnetic simulations confirm that the lowest-energy modes are localized within ∼ 15-nm-wide regions at the edges of the strips and their frequencies can be tuned in a wide range (up to 5 GHz) by changing the magnetostatic coupling (i.e., spatial separation) between the microstrips. [ABSTRACT FROM AUTHOR]

Magnetic skyrmions are topologically protected spin swirling vertices, which are promising in device applications due to their particle‐like nature and excellent controlability. Magnetic skyrmions are extensively studied in a variety of materials and proposed to exist in the extreme 2D limit, i.e., in twisted bilayer CrI3 (TBCI). Unfortunately, the magnetic states of TBCIs with small twist angles are disorderly distributed ferromagnetic and antiferromagnetic (AFM) domains in recent experiments, and thus the method to get rid of disorders in TBCIs is highly desirable. Here, intralayer exchange interactions up to the third nearest neighbors without empirical parameters and very accurate interlayer exchange interactions are used to study the magnetic states of TBCIs. The functions of interlayer exchange interactions obtained using first‐principles calculations and stored in symmetry‐adapted artificial neural networks are proposed. Based on these, the subsequent Landau–Lifshitz–Gillbert equation calculations explain the disorderly distributed FM‐AFM domains in TBCIs with small twist angles and predict the orderly distributed skyrmions in TBCIs with large twist angles. This novel twisted 2D bilayer magnet can be used to design memory devices, monochromatic spin wave generators and many kinds of skyrmion lattices. [ABSTRACT FROM AUTHOR]

The article presents a discovery of interconnected emergent magnetic molecular orbitals in a simple binary compound manganese monosilicide (MnSi) using inelastic neutron scattering (INS). Topics discussed include sample growth and characterization, an overview of INS, electronic structure, and maximally localized Wannier functions (MLWF) calculations.

Using experimental and numerical investigation, we demonstrate laser-controlled propagation and interaction of spin waves in an irregular magnetic structure in the geometry of the Mach–Zehnder interferometer. It is shown that the use of laser radiation for heating one of the interferometer arms leads to controlled interference of a spin-wave signal in the output section. The yttrium–iron garnet film heating under the action of laser radiation is measured experimentally. Using micromagnetic modeling, the evolution of the spin-wave interference pattern under the action of laser heating of one of the interferometer arm is demonstrated. The results of this study ensure a simple solution for developing tunable spin-wave interferometers for the paradigm of the magnonic logics. [ABSTRACT FROM AUTHOR]

The effect of annealing at room temperature on the fluctuation conductivity (FLC) σ′(T) and pseudogap (PG) Δ*(7) in the basal ab plane of ReBa2Cu3O7–δ (Re = Ho) single crystals with a lack of oxygen has been studied. It is shown that at all stages of annealing, the FLC near Tc can be described by the Aslamazov-Larkin and Maki-Thompson fluctuation theories, demonstrating a 3D-2D crossover with increasing temperature. The crossover temperature T0 was used to determine the coherence length along the c axis, ξc(0) = (2.82 ± 0.2) Å. At the intermediate stage of annealing, an anomalous increase in 2D FLC was revealed, which is associated with the influence of uncompensated magnetic moments in HoBa2Cu3O7–5 (HoBCO): μeff, Ho = 9.7μΒ. For the quenched sample S1, the temperature dependence of the PG has a shape typical of single crystals with a large number of defects. However, Δ*(T) has two small additional maxima at high temperature, which is a feature of HoBCO single crystals with pronounced twins and indicates the two-phase nature of the sample. Upon annealing, the shape of Δ*(T) noticeably changes, very likely due to an increase in the magnetic interaction (sample S2). More important is the change in the slope of the data at high temperatures, which has become about 3.5 times steeper. The ordering of the oxygen distribution due to the diffusion process during annealing somewhat compensates for the influence of magnetic interaction. But the slope does not change (sample S3). Interestingly, the slope turns out to be the same as for FeAs-based superconductors, suggesting the possibility of the existence of spin density waves in HoBCO in the PG state. The comparison of the pseudogap parameter Δ ∗ (T) / Δ max ∗ near Tc with the Peters-Bauer theory revealed a slight increase in the density of local pairs < n↑n↓>, which should explain the observed increase in Tc by 9 K during annealing. [ABSTRACT FROM AUTHOR]

Being able to accurately control the interaction of spin waves is a crucial challenge for magnonics in order to offer an alternative wave-based computing scheme for certain technological applications. Especially in neural networks and neuromorphic computing, wave-based approaches can offer significant advantages over traditional CMOS-based binary computing schemes with regard to performance and power consumption. In this work, we demonstrate precise modulation of phase- and amplitude-sensitive interference of coherent spin waves in a yttrium–iron–garnet based magnonic analog adder device, while also showing the feasibility of frequency-division multiplexing. Using time-resolved scanning transmission x-ray microscopy, the interference was directly observed, giving an important proof of concept for this kind of analog computing device and its underlying working principle. This constitutes a step toward wave-based analog computing using magnons as an information carrier. [ABSTRACT FROM AUTHOR]

Samples (Cu0.5Tl0.5)Ba2Ca2Cu3-xKxO10-δ (x = 0, 1, 2, 2.5, 3) and Tl1.0Ba2Ca2K3O10-δ were synthesized to study the effect of electron donor atoms at the copper planar sites CuO2 to better understand process of superconductivity in oxides. The samples were synthesized following the two-step solid-state reaction method, and analyzed using x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray fluorescence spectroscopy (XRF), resistivity (RT), and Fourier-transform infrared (FTIR) absorption measurements. By using the software VESTA (visualization for electronic and structural analysis), we have successfully drawn the crystal structures of all the samples. From room temperature to the onset of superconductivity, our samples showed metallic variation in resistivity, with zero resistivity at the critical temperature (Tc, R = 0) staying around 93 K. In the Tl1.0Ba2Ca2K3O10-δ samples, copper Cu (3d9) atoms were entirely removed from the charge reservoir layer (i.e., Tl1.0Ba2O4-δ charge reservoir layer) the samples showed semiconducting behavior with variable range Mott hopping (VRH) conductivity with an energy gap of 2.41 meV. The FTIR absorption spectrum demonstrated the planar oxygen mode, as well as the apical oxygen modes. Tl-OA-Cu(2) and Cu(1)-OA-Cu(2) were stiffened with the doping of K(4s1) at the CuO2 planar sites, confirming intrinsic doping of K atoms. Excess conductivity studies (FIC) of the Cu0.5Tl0.5Ba2Ca2Cu3-xKxO10-δ (x = 1, 2, 2.5, 3) samples revealed an increase in the coherence length along the c-axis ξc(0), the Fermi velocity of superconducting carriers VF, inter-layer coupling J, and the energy needed to break apart the Cooper pairs when compared with the un-doped Cu0.5Tl0.5Ba2Ca2Cu3O10-δ, sample. Doped alkali atoms provide a larger density of free carriers in the superconducting planes rising superconductivity parameters. Higher free carrier density provided by the doped alkali atoms at room temperature to the conducting planes enhanced the electron–hole recombination process which brings them to the optimal doping level, thereby promoting the critical temperature and superconducting parameters to superior values. The Turning of the Tl1Ba2Ca2K3O10-δ samples semiconducting has shown that the presence of a spin-bearing entity in the unit cell is important for the occurrence of high Tc superconductivity, and the interplay of spin and charge density waves induces superconductivity in oxide samples at high temperatures. [ABSTRACT FROM AUTHOR]

The dependence of nonreciprocity of excitation of magnetostatic surface waves on antenna width was investigated experimentally and theoretically. The nonreciprocity was successfully modified by changing the excitation antenna width. The nonreciprocity ratio, which was defined as the spin wave intensity under negative bias field divided by that under positive bias field, was found to decrease with increasing antenna width. Micromagnetic simulations revealed that this decrease in the nonreciprocity ratio originates from the rapid decrease in the in-plane excitation field compared to the perpendicular excitation field with reducing the antenna width. [ABSTRACT FROM AUTHOR]

In this work, we consider dispersion laws of spin waves that propagate in a ferromagnet/superconductor bilayer, specifically in a ferromagnetic film coupled inductively to a superconductor. The coupling is viewed as an interaction of a spin wave in a ferromagnetic film with its mirrored image generated by the superconductor. We show that, in general, the coupling enhances substantially the phase velocity of magnons in in-plane spin wave geometries. In addition, a heavy nonreciprocity of the dispersion law is observed in the magnetostatic surface spin wave geometry where the phase velocity depends on the direction of the wave propagation. [ABSTRACT FROM AUTHOR]

The purpose of this numerical study, performed within the micromagnetic framework and the dynamical matrix method, is to understand how the propagation of spin waves in a macrospin chain is affected by a configurational rearrangement of the magnetization, induced by a progressive variation of a magnetic field. Our macrospins are modelized through thin cylinders with elliptical cross sections that display a monodomain, bistable magnetization distribution; hence, the allowed magnetization configurations of the chain are either antiferromagnetic (AF) or ferromagnetic (FM). We illustrate the peculiar features of spin waves in the AF and FM configurations concerning the dispersion relations, phase amplitude variations and localization, and precession ellipticity, as a function of the applied field, particularly close to the critical field values at which the configurational rearrangements occur (AF-to-FM or vice versa). A remarkable effect that arises on the mode frequency and bandwidth across a configurational transition is the frequency invariance of specific Bloch waves, particularly attractive for processing the spin wave signals in low dissipation magnon-spintronic devices. [ABSTRACT FROM AUTHOR]

A detailed analytical and numerical study of the spin wave modes of two nanopillar spin torque nano-oscillators coupled by magnetostatic interactions is presented under the macrospin approximation. Results show that the normal modes of the system oscillate with the magnetizations in-phase or anti-phase in both disks. The frequencies and critical current densities necessary to induce auto-oscillations of the spin wave modes of the coupled system depend on the relative position of the nanopillars and the applied magnetic field. If the oscillators are identical, these modes are degenerate at a certain relative position of the nanopillars, while if the oscillators are non-identical, such degeneracy is removed. Then, we can conclude that the magnetostatic coupling between two spin transfer torque nano-oscillators is a powerful mechanism to control the spin wave modes of these systems. [ABSTRACT FROM AUTHOR]

We propose a new type of a spin waveguide in yttrium iron garnet solely controlled by external electric fields. Spin waves are generated by microwave electric fields while the shift of the phase between spin waves is achieved by means of static electric fields. The phase shifter operation is based on the magneto-electric coupling and effective Dzyaloshinskii Moriya interaction. The special geometry of the waveguide imposes certain asymmetry in the dispersion relationships of the spin waves. Depending on the propagation direction, the phases of the spin waves are shifted differently by the external electric field. The phase difference is entirely controlled by the driving electric fields. The proposed phase shifter can be easily incorporated into electronic circuits and in spin wave logical operations. [ABSTRACT FROM AUTHOR]

Magnetic heterostructures consisting of single-crystal yttrium iron garnet (YIG) films coated with platinum are widely used in spin-wave experiments related to spintronic phenomena such as the spin-transfer-torque, spin-Hall, and spin-Seebeck effects. However, spin waves in YIG/Pt bilayers experience much stronger attenuation than in bare YIG films. For micrometer-thick YIG films, this effect is caused by microwave eddy currents in the Pt layer. This paper reports that by employing an excitation configuration in which the YIG film faces the metal plate of the microstrip antenna structure, the eddy currents in Pt are shunted and the transmission of the Damon-Eschbach surface spin wave is greatly improved. The reduction in spin-wave attenuation persists even when the Pt coating is separated from the ground plate by a thin dielectric layer. This makes the proposed excitation configuration suitable for injection of an electric current into the Pt layer and thus for application in spintronics devices. The theoretical analysis carried out within the framework of the electrodynamic approach reveals how the platinum nanolayer and the nearby highly conductive metal plate affect the group velocity and the lifetime of the Damon-Eshbach surface wave and how these two wavelength-dependent quantities determine the transmission characteristics of the spin-wave device. [ABSTRACT FROM AUTHOR]

In this paper, spin-to-charge current conversion properties in the Weyl semimetal TaP by means of the inverse Rashba-Edelstein effect (IREE) with the interfacial integration of this quantum material with the ferromagnetic metal Permalloy (Py = Ni81Fe19) are presented. The spin currents are generated in the Py layer by the spin pumping effect (SPE) from microwave-driven ferromagnetic resonance and are detected by a dc voltage along the TaP crystal, at room temperature. A field-symmetric voltage signal is observed without the contamination of asymmetrical lines due to spin rectification effects observed in studies using metallic ferromagnets. The observed voltage is attributed to spin-to-charge current conversion based on the IREE, made possible by the spin-orbit coupling induced intrinsically by the bulk band structure of Weyl semimetals. The measured IREE coefficient λIREE = (0.30 ± 0.01) nm is two orders of magnitude larger than in graphene and is comparable to or larger than the values reported for some metallic interfaces and for several topological insulators. [ABSTRACT FROM AUTHOR]

Topological electronic materials hold great promise for revolutionizing spintronics, owing to their topological protected, spin-polarized conduction edge or surface state. One of the key bottlenecks for the practical use of common binary and ternary topological insulator materials is the large defect concentration that leads to a high background carrier concentration. Elemental tin in its α-phase is a room temperature topological semimetal, which is intrinsically less prone to defect-related shortcomings. Recently, the growth of ultrathin α-Sn films on ferromagnetic Co surfaces has been achieved; however, thicker films are needed to reach the 3D topological Dirac semimetallic state. Here, the growth of α-Sn films on Co at cryogenic temperatures was explored. Very low-temperature growth holds the promise of suppressing undesired phases, alloying across the interfaces, as well as the formation of Sn pillars or hillocks. Nevertheless, the critical Sn layer thickness of ≈3 atomic layers, above which the film partially transforms into the undesired b-phase, remains the same as for room-temperature growth. From ferromagnetic resonance studies, and supported by electron microscopy, it can be concluded that for cryogenic Sn layer growth, the interface between Sn and Co remains sharp and the magnetic properties of the Co layer stay intact. [ABSTRACT FROM AUTHOR]

The results of experimental and theoretical studies of standing spin waves in a series of epitaxial films of the ferromagnetic Pd1−xFex alloy (0.02 < x < 0.11) with different distributions of the magnetic properties across the thickness are presented. Films with linear and stepwise, as well as more complex Lorentzian, sine and cosine profiles of iron concentration in the alloy, and thicknesses from 20 to 400 nm are considered. A crucial influence of the magnetic properties profile on the spectrum of spin wave resonances is demonstrated. A capability of engineering the standing spin waves in graded ferromagnetic films for applications in magnonics is discussed. [ABSTRACT FROM AUTHOR]

Active control of propagating short-wavelength spin waves in perpendicularly magnetized materials is promising for designing nanoscale magnonic devices. One method of manipulating spin waves on the nanoscale is through their interaction with magnetic textures, an example of which is the magnetic skyrmion—a particle-like topological object stabilized in thin film heterostructures by the Dzyaloshinskii–Moriya interaction (DMI) and perpendicular magnetic anisotropy. In this paper, the interaction between spin waves and skyrmions is studied using micromagnetic simulations. The magnetic parameters chosen are similar to those found experimentally, leading to a skyrmion with an extended core of reversed magnetization. The effect of a propagating spin wave on the skyrmion is to cause the emission of a secondary spin wave by the skyrmion. At low frequencies, where the incoming spin wave wavelength is much larger than the skyrmion, this leads to a nearly circular re-emitted spin wave. The pattern of emission becomes increasingly complex at higher frequencies as the wavelength becomes similar to the skyrmion size due to the complex excitation of the extended core. The emitted spin wave profile can be controlled by altering the size of the skyrmion through the magnitude of the DMI, providing a method of tuning the system. [ABSTRACT FROM AUTHOR]

Spin waves are studied intensively for their intriguing properties and potential use in future technology platforms for the transfer and processing of information and microwave signals. The characterization of devices and materials for magnonic systems is time-consuming, and thus, the development of instruments that can speed up the collection and analysis of spin-wave data is crucial. In this Letter, we report a straightforward approach to enhance the measurement throughput by fully exploiting the wideband detection nature of the Brillouin light scattering technique with a white-noise RF generator. [ABSTRACT FROM AUTHOR]

The optical method of spin dynamics measurements via the detection of various magneto-optical effects is widely used nowadays. Besides it being a convenient method to achieve time-resolved measurements, its spatial resolution in the lateral direction is limited by a diffraction limit for the probe light. We propose a novel approach utilizing a Mie-resonance-based all-dielectric metasurface that allows for the extraction of a signal of a single submicron-wavelength spin wave from the wide spin precession spectra. This approach is based on the possibility of designing a metasurface that possesses nonuniform magneto-optical sensitivity to the different nanoscale regions of the smooth magnetic film due to the excitation of the Mie modes. The metasurface is tuned to be unsensitive to the long-wavelength spin precession, which is achieved by the optical resonance-caused zeroing of the magneto-optical effect for uniform magnetization in the vicinity of the resonance. At the same time, such a Mie-supporting metasurface exhibits selective sensitivity to a narrow range of short wavelengths equal to its period. [ABSTRACT FROM AUTHOR]

It is indicated that when a circularly polarized electromagnetic wave is incident obliquely on an ideal conductor and reflected from it, the spin of the wave is partially transferred to the conductor. In this case, if the conductor rotates so that the axis of rotation is parallel to the transferred spin, then work is done. The work leads to a change in the frequency of the wave, and this can be recorded in a suitable interference experiment by shifting the interference fringes. [ABSTRACT FROM AUTHOR]

Spin torque nano-oscillator has been extensively studied both theoretically and experimentally in recent decades due to its potential applications in future microwave communication technology and neuromorphic computing. In this work, we present a skyrmion-based spin torque nano-oscillator driven by a spatially uniform direct current, where an elongated skyrmion is confined by two pinning sites. Different from other skyrmion-based oscillators that arise from the circular motion or the breathing mode of a skyrmion, the steady-state oscillatory motion is produced by the periodic deformation of the elongated skyrmion, which originates from the oscillation of its partial domain walls under the joint action of spin torques, the damping and the boundary effect. Micromagnetic simulations are performed to demonstrate the dependence of the oscillation frequency on the driving current, the damping constant, the magnetic parameters as well as the characteristics of pinning sites. This nonlinear response to a direct current turns out to be universal and can also appear in the case of elongated antiskyrmions, skyrmioniums and domain walls. Furthermore, the elongated skyrmion possesses a rectangle-like domain wall, which could also serve as a magnonic waveguide. These findings will enrich the design options for future skyrmion-based devices in the information technology. Spin torque nano-oscillators facilitate the control of magnetization dynamics without the need for an external magnetic field and are compatible with CMOS technologies. Here, the authors propose, using micromagnetic simulations, a device comprising of an elongated-skyrmion-based spin torque nano-oscillator, which can be controlled using a spatially uniform current. This elongated skyrmion can also serve as a magnonic waveguide. [ABSTRACT FROM AUTHOR]