High-frequency and fast-propagating antiferromagnetic magnons hold significant potential for ultrafast spintronic technologies, particularly at terahertz frequencies. While conventional electrical methods for exciting antiferromagnetic magnons are limited in coherence, frequency range, and wavevector control, optical approaches offer significant opportunities to overcome these constraints. Here, we report the first observation of nonreciprocal magnon propagation in a canted antiferromagnet α-Fe2O3 at sub-terahertz frequencies. Using ultrafast optical excitation and Bragg-selective magneto-optical Kerr detection, we reveal distinct propagation dynamics for quasi-ferromagnetic and quasi-antiferromagnetic magnons at room temperature. Notably, the quasi-ferromagnetic magnon exhibits pronounced nonreciprocity and a record-high group velocity (33 km s−1). The amplitude nonreciprocity arises primarily from the asymmetric dipolar interaction enhanced by the Dzyaloshinskii–Moriya interaction, as supported by theoretical calculations. These findings establish fundamental principles for ultrafast and directional control of antiferromagnetic magnons, paving the way for high-frequency spintronic applications. The authors demonstrate that optically excited subterahertz magnons in canted antiferromagnetic hematite propagate nonreciprocally at high group velocities, offering potential for ultrafast spintronic applications.

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.

The synthesis of NiFe2O4+delta crystals under varying oxygen pressures has been systematically investigated to understand their impact on elemental composition, crystal structure, and ferromagnetic resonance spectra. Using the optical floating zone melting technique, bulk single crystals were grown under oxygen pressures of 15, 20, and 30 MPa, followed by annealing in air to achieve different oxygen stoichiometries. X-ray diffraction analysis revealed a cubic crystal structure with lattice parameters influenced by oxygen intercalation, while energy-dispersive X-ray spectroscopy confirmed variations in Fe/Ni ratios, indicating the presence of excess oxygen. Ferromagnetic resonance (FMR) spectra showed tunable resonance frequencies between 5 and 15 GHz under applied magnetic fields, with optimal properties observed for samples synthesized at 15 MPa and annealed for 24 h. These samples exhibited the narrowest FMR linewidth (295 Oe) and the highest absorption intensity, making them promising candidates for spintronic applications such as filters and detectors.

Recent advances in magnon spintronics have ignited interest in the interactions between the spin and elastic subsystems of magnetic materials. These interactions suggest a dynamic connection between collective excitations of spins, quantized as magnons, and elastic waves generated by perturbations in the crystal lattice, quantized as phonons. Both magnons and their associated magnon-phonon excitations can act as sources of spin pumping from magnetic materials into non-magnetic metals. Although a considerable body of research has focused on spin pumping via elastic waves in ferromagnets, similar investigations involving antiferromagnets have yet to be undertaken. In this work, we experimentally demonstrate for the first time the feasibility of generating spin currents at ultrasonic frequencies of acoustic resonance in antiferromagnetic crystal hematite α-Fe_2O_3 at room temperature. We provide both theoretical and experimental evidence that, due to strong magnetoelastic coupling, acoustic vibrations in hematite induce significant variable deviations in magnetization, resulting in spin accumulation at the antiferromagnet-normal metal interface, which in turn leads to the generation of spin and charge currents in the metal. Charge currents arising from the inverse spin Hall effect can be measured using the same methodology employed under high-frequency spin pumping conditions at the resonances of the magnetic subsystem itself. Moreover, the acoustic resonance in hematite is significantly more pronounced (by hundreds or even thousands of times) than in other quasiferromagnetic or antiferromagnetic systems, enabling the attainment of extremely large amplitudes of magnetic oscillations for spin pumping. This research highlights the new approach of utilizing acoustic spin pumping to manipulate spin currents in magnetic materials, particularly antiferromagnets.

The development of a terahertz signal source operating at room temperature and having the ability to widely tune the frequency is an important scientific task. In this work, we theoretically justify the need for an experiment to observe an antiferromagnetic spin Hall oscillator (AFM SHO) with different easy plane orientations as an essential and integral step towards the creation of such terahertz signal sources. Here, we analyze both analytically and numerically the mathematical model for the canted AFM SHO with different positions of the easy plane and also verify the obtained results using micromagnetic simulations. We obtain analytical expressions for critical currents of the onset of self-oscillations and the end of damping oscillations and show that they both increase as the AFM easy plane approaches either of the two planes containing the spin current polarization vector.

The electric and magnetic frequency rearrangement of a Bragg resonance in the spectrum of spin waves in a magnonic crystal in the form of 100-nm-thick yttrium iron garnet film with attached 10-nm-thick platinum strips is reported. The effect of the spin current on the position of the Bragg band gap depends on the polarity of the voltage applied to the platinum strips. The positive voltage does not affect the band gap position, while the applied negative voltage lowers the band gap by about of 5 MHz. At frequencies outside the band gap, depending on the polarity of the voltage applied to platinum, either the enhancement or suppression of the spin wave is observed.

The paper presents the results of a theoretical study of the dispersion characteristics of electromagnetic waves (EMW) existing in a transversely magnetized antiferromagnetic (AFM) semiconductor with loss. An AFM semiconductor is an infinite bi-gyrotropic medium, the effective material parameters of which are twice negative in several frequency ranges. It was found that these frequency bands are in the terahertz range, and there are four backward EMEs in them, two of which are TE waves, and the other two are TM waves.

Unidirectional information transport is often realized in magnonic application using the filters, isolators, and circulators. In this Letter, we propose the simple design of the unidirectional magnonic coupler, which is realized as a laterally coupled yttrium–iron–garnet waveguide coated with a metal layer. We experimentally discover and numerically confirm that the proposed structure can exhibit unidirectional coupling, which can be easily controlled by the direction of the external magnetic field. At the same time, we show how the dynamic magnetization profile of the spin wave is varied with the change in the propagation direction to the opposite along the coupler. Brillouin light scattering reveals the variation of the spatial spin-wave profile, which is then used to extract the value of the coupling length. The experimental results are in good agreement with the results of the coupling length estimation from two methods: eingenmode analysis and Landau–Lifshits–Gilbert solution in parallel with the Maxwell equations. This opens up alternative ways to fabricate the non-reciprocal magnonic devices. In particular, we consider the operation of the unidirectional magnonic coupler as a multi-regime logic device.

The impact of bias magnetic field on the nonlinearity of ferromagnetic thin films is investigated. Using the methods of Hamiltonian formalism, an analytical expression for the nonisochronicity coefficient is obtained taking into account perpendicular magnetic anisotropy. We show that in films with high perpendicular magnetic anisotropy, an effective adjustment ofthe nonlinearity can be performed by a lower bias magnetic field. Theoretically obtained results are verified by micromagnetic simulations.

Antiferromagnetic (AFM) materials possess a well-recognized potential for ultrafast data processing thanks to their intrinsic ultrafast spin dynamics, absence of stray fields, and large spin transport effects. The very same properties, however, make their manipulation difficult, requiring frequencies in THz range and magnetic fields of tens of Teslas. Switching of AFM order implies going into the nonlinear regime, a largely unexplored territory. Here we use THz light from a free electron laser to drive antiferromagnetic NiO into a highly nonlinear regime and steer it out of nonlinearity with magnetic field from a 33-Tesla Bitter magnet. This demonstration of large-amplitude dynamics represents a crucial step towards ultrafast resonant switching of AFM order.

In this work, we present the results of a systematic experimental study of linear and parametric spin wave resonant excitation accompanied by spin currents (spin pumping) in a multifrequency composite bulk acoustic wave resonator with a ZnO-YIG-GGG-YIG/Pt structure. The features of magnetic dynamics excitation in YIG films due to magnetoelastic coupling with acoustic thickness modes of various polarizations are studied. Acoustic spin waves and spin pumping are detected by simultaneous frequency-field mapping of the inverse spin Hall effect voltage and the resonant frequencies of thickness extensional modes. In the parametric range of frequencies and fields, acoustic spin pumping induced by both shear and longitudinal polarization modes was observed. Linear acoustic spin waves are excited only by shear thickness extensional modes because longitudinal acoustic waves do not couple with the magnetic subsystem in linear regime.

Spin pumping from canted antiferromagnets is a cutting-edge topic in modern spintronics. The interest for fundamental and applied research that these materials arouse is related to their unusual structure, namely, with a small canting of the magnetic sublattices, which is explained by the presence of the Dzyaloshinskii–Moriya interaction. Through this effect, it becomes possible to experimentally study quasi-ferromagnetic resonance spectra and spin pumping in the range of tens of GHz at room temperature. In this paper, an experimental and theoretical investigation of spin pumping from an antiferromagnet with weak ferromagnetism, α-Fe2O3, is carried out. The conversion of the precession of the magnetization vector, excited by an alternating magnetic microwave field, into a constant voltage is realized using the inverse spin Hall effect in the hematite/heavy metal structure. Using a constant magnetic field up to 5 kOe, the resonant frequency of such a detector is tunable over a wide range up to 32 GHz with potential sensitivity reaching 10.1 μV/W. Confirmation of the measurement of the spin current is the change in the sign of Vsp when the polarity of the constant magnetic field alters. We believe that these studies will make a major contribution to the understanding of the physics of the spin-pumping effect from antiferromagnets and will also help in the development of devices for quantum technologies and next-generation communication technologies.

We investigated the possibilities of controlling the nonlinear frequency shift of the magnetization oscillations in a spin-transfer nanoscillator by varying the magnitude and direction of the bias magnetic field. We considered both isotropic ferromagnetic materials and crystals with uniaxial and cubic crystallographic anisotropies. We have shown that achieving a zero nonlinear frequency shift is possible with a certain orientation of the bias magnetic field vector. The results of the theoretical analysis based on the method of Hamiltonian formalism are in good agreement with the micromagnetic simulations. Our research reveals the way to control the frequency tuning of a spin transfer nanoscillator, which is crucial for spintronic signal generation devices.

We propose the design of single-layer, double-layer, and triple-layer configurations of magnonic ring couplers, which perform spin-wave mode filtering and provide interlayer signal transmission in threedimensional architectures of magnonic integrated circuits. We study the characteristics of spin-wave dynamics in coupled magnonic structures with a ring resonator in planar and vertical configurations using Brillouin light scattering and the micromagnetic simulation method based on numerical solution of the Landau-Lifshitz-Gilbert equation. The mechanisms of backward and forward coupling control of spin-wave transport in yttrium iron garnet stripe placed in the proximity of the magnonic microring resonator are elucidated. The possibility of reversing the direction of spin-wave propagation with simultaneous selection of transverse spin-wave modes is demonstrated. It is shown that, in the proposed structure, multistream selection of a spin-wave signal is possible due to spatial frequency and simultaneous mode separation. Lateral and vertical magnonic rings could be used for magnonic logic application with the variation of the phase and amplitude of signals. We also demonstrate that the spin-wave mode order is an additional parameter that can be used to simultaneously control the transmission of the ring coupler with the facility to encode the logical state "0" or "1" with the width mode order. The multistream selection of a spin-wave signal and the spatial frequency and simultaneous mode separation lie behind the application of the proposed magnonic ring coupler as a multiport interconnection element and/or functional logical unit in reconfigurable integral blocks of magnonic networks.

The main features of the nonlinear pulse propagated in iron-yttrium-garnet magnonic crystal with thickness 100 nm and a periodic system of grooves on the surface are studied. We have demonstrated the possibility of the formation of gap solitons at a frequency inside the band gap of the magnonic crystal when the input signal power is increased. A further increase in the duration and power of the input pulse leads to the formation a series of gap solitons with a duration of about 10 ns. We have discovered that the threshold power of the gap solitons' generation is determined by the magnitude of the magnetic field.

Spin pumping by surface and backward volume magnetostatic waves in YIG/Pt structures is experimentally studied and analyzed. It is shown that at frequencies corresponding to van Hove singularities in the density of states of the spin wave spectrum, an increase in the efficiency of electron-magnon scattering and spin current generation takes place. The obtained results are important for spin wave-based spintronic devices development.

Recently, canted antiferromagnets offer great potential for fundamental research and applications due to their unique properties. The presence of the Dzyaloshinskii-Moriya interaction leads to the existence of a weak ferromagnetic moment at room temperature. We study both theoretically and experimentally microwave spin pumping by the quasi-ferromagnetic mode from a canted easy plane antiferromagnet with weak ferromagnetism FeBO3. The conversion of a microwave signal into the constant voltage is realized using the inverse spin Hall effect in an iron borate/heavy metal heterostructure. We use an additional bias magnetic field to selectively tune the resonance frequency of such a microwave detector over a wide range up to 43.5 GHz with potential sensitivity near 2.5 microV/W. We confirm the pure spin current nature by changing polarity of the detected via inverse spin Hall effect voltage by switching the direction of the bias magnetic field. We believe that our results will be useful for the development of highly tunable, portable and sensitive microwave antiferromagnet-based functional devices.

In this work, we present the results of investigations performed on hematite (α-Fe2O3), which is an antiferromagnet with weak ferromagnetism. Through the use of Brillouin light scattering spectroscopy, we studied experimentally the excitation of quasi-ferro- and antiferromagnetic modes in the bulk hematite. We investigated the influence of relative mechanical strains, ϵyy, on the frequencies of quasi-ferro- and antiferromagnetic modes. Also, we considered the angular dependence of the frequency of the quasi-ferromagnetic mode on the external magnetic field. Our results indicate that hematite is a suitable material for strain-controlled magnonic devices.

Microwave spin pumping from ferromagnetic lutetium iron garnet (Lu3Fe5O12) has been theoretically and experimentally investigated. The magnetization vector precession excited by a microwave magnetic field is transformed into a dc voltage due to the inverse spin Hall effect in the lutetium iron garnet/heavy metal heterostructure (Lu3Fe5O12/Pt). In the experiments carried out, the external magnetic field has been varied from 0 to 6 kOe, thus making it possible to tune the resonant frequency in wide ranges. The experimental sensitivity of this heterostructure is 8.2 µV/W. A change in the dc voltage sign with a change in the magnetic field direction confirms the generation of spin current in the Lu3Fe5O12/Pt heterostructure. The results obtained make a significant contribution to insight into spin pumping physics and may be useful for the development of new highly sensitive tunable spintronic devices.