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 purpose the purpose of this study is to mathematically describe an ensemble of oscillators coupled by a common dipole field, to model and study the synchronization of the three topologies under consideration: a ring, a grid, and a special case of a lattice-chain, with subsequent identification of a priority topology that would ensure synchronization over a larger range of initial conditions of the ensemble. Methods. To simplify the numerical modeling and study the synchronization of systems of antiferromagnetic oscillators coupled by a common dipole field, the Kuramoto model for coupled oscillators, as well as the order parameter and its average value, were used. Results. A mathematical model for antiferromagnetic oscillators coupled by a common dipole field was obtained for three topologies: ring, grid, and chain. Using the Kuramoto model of coupled oscillators and the order parameter and its average value, the synchronization of the considered arrays was studied, and it was found that the lattice is the preferred topology for the same ensemble parameters. Conclusion. The paper studies the problem of synchronization of ensembles of antiferromagnetic spin-Hall oscillators (AFM SCHO) combined into different topologies: ring, grid and chain. It is shown that the grid is the most preferable topology for achieving synchronization at lower values of the coupling strength constant between the moscillators. The ring and chain require higher values of the coupling strength constant, which is their disadvantage. Nevertheless, with a sufficiently strong coupling, synchronization is also possible in these topologies.

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.

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 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.

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.

Introduction. The use of spintronic components significantly enhances the performance, reduces the size, and lowers the power consumption of modern electronic devices. The spintronic oscillator (SO) is an integral part of spintronic devices. Connecting several SOs (> 100) into ensembles with subsequent synchronization mitigates such SO drawbacks as low output power and high phase noise. These drawbacks appear as a result of an increase in the output power of an SO ensemble compared to a single oscillator under a simultaneous decrease in the spectral linewidth of the ensemble.Aim. To investigate the impact of connection topologies, synchronization mechanisms, and oscillator failures on the synchronization of oscillator ensembles.Materials and methods. The Kuramoto phase model was used to simplify the numerical modeling of synchronization of SOs connected into an ensemble.Results. A Kuramoto equation for phases of SOs connected in an ensemble was derived, and the influence of connection topologies and oscillator failures on the synchronization parameters of an ensemble of N connected oscillators was demonstrated.Conclusion. In order to ensure the shortest transition time of an SO ensemble to the synchronous mode, topologies with a higher number of connections between oscillators (e.g., "all-to-all") are preferable. The results obtained confirm the advantages of local connection of an SO ensemble by a common current, thus forming an "all-to-all" topology. This makes the transition time of the SO ensemble to the synchronous mode less dependent on both oscillator failures and the number of synchronized SOs.

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.

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.

The influence of sintering time (T=1000 °C, t=0, 24, 48 hours) in an oxygen atmosphere (15 atm.) on the lattice parameter (a≈8.34 Å), saturation magnetization (22, 36, 32 emu/g), coercive force (4, 6, 3 Oe) of static hysteresis loops, and the dependence of resonance frequency on the magnetic field for grown single crystals of NiFe 2 O 4 has been investigated.

An epitaxial heterostructure based on strontium and lanthanum-strontium manganite films (SrMnO3 and La0.7Sr0.3MnO3) is studied. Ferromagnetic resonance spectra, angular dependences of the resonance field for different temperatures, in-plane and cubic anisotropy as well as the temperature dependences of the magnetization, were measured. The obtained magnetic parameters of the heterostructure were compared with the magnetic parameters of a single La0.7Sr0.3MnO3 film. We assume that the existence of an interlayer exchange at the ferromagnet-antiferromagnet interface at low temperatures leads to the appearance of unidirectional anisotropy in the heterostructure SrMnO3/La0.7Sr0.3MnO3. We believe that the presented results will be useful for the practical development of antiferromagnet-based ultrafast devices: emitters, amplifiers, detectors.

We present a model of a sub-THz frequency spectrum analyzer based on the antiferromagnet/non–magnetic metal heterostructure. The considered structure operates in the active self–oscillation regime with the high Q–factor (closed to $10^{6}$ ) and is phase–locked to the analyzed signal, while the frequency of the oscillator is linearly tuned by the spin–polarized current flowing through the non–magnetic metal. We find an analytical expression for the duration of the phase–locking interval by analyzing the generalized Kuramoto model with inertia. We show that the speed of the described spectrum analyzer is comparable to and exceeds the speed of modern commercial spectrum analyzers. The presented results can be helpful for practically realizing the room–temperature, tunable, sensitive, and high–speed sub-THz frequency spectrum analyzers.

Introduction . The characteristics of solid-state microwave switches are subject to different requirements depending on the application area and technical problems to be solved. No versatile solution exists that could satisfy all requirements at once. The desire to improve the parameters of switches has led to the emergence of devices based on various technologies. In order to elucidate the current trends and future prospects in the field of switch technologies, semiconductor devices that form the basis of switch circuits should be considered. Aim . To review transistor types used in solid-state switches. Materials and methods . The search and selection of literature sources for review was based on the chronological principle. The search depth for considering the parameters of finished components was no more than 10 years, for considering technologies and structural solutions – more than 10 years. This choice was explained by our desire to trace the history of development and approaches to the creation of semiconductor devices that have led to the emergence of the modern component base. The final array of sources comprised scientific publications presenting factual information on the objects under consideration. Results . The types, structures, materials, characteristics and manufacturing technologies of transistors used in switches are considered. The achievable parameters of the switches based on the considered devices are presented. Conclusion . The choice of a particular transistor type for switches depends on the requirements for the parameters and performance characteristics of the final device. At present, transistor solutions for switches are dominated by field-effect transistors (FETs) of various types: GaAs and GaN transistors with a high electron mobility (HEMT) and Si CMOS FETs implemented by standard as well as silicon-on-insulator and silicon-on-sapphire technologies. The conducted literature review has revealed prospects for the development of technologies based on BiCMOS heterojunction bipolar transistors.

Эпитаксиальная гетероструктура на основе манганитных пленок стронция и лантана-стронция (SrMnO3 и La0.7 Sr0.3 MnO3 ) изучалась в данной работе. Измерены спектры ферромагнитного резонанса, угловые зависимости резонансного поля при различных температурах, плоскостная и кубическая анизотропия, а также температурные зависимости намагниченности. Полученные магнитные параметры гетероструктуры сравнивались с магнитными параметрами одиночной пленки La0.7 Sr0.3 MnO3. Мы предполагаем, что наличие межслоевого обмена на границе раздела ферромагнетик-антиферромагнетик при низких температурах приводит к возникновению однонаправленной анизотропии в гетероструктуре SrMnO3/La0.7 Sr0.3 MnO3. Мы полагаем, что представленные результаты будут полезны для практической разработки сверхбыстродействующих устройств на основе антиферромагнетиков: излучателей, усилителей, детекторов.

In this work we present a model explaining the properties of magnetoelastic waves propagation in the heterostructure containing an antiferromagnetic layer on a non-magnetic elastic substate. Horizontally polarized shear surface waves (SH-waves) propagating in thin film are Love waves. The dispersion characteristic of magnetoelastic waves in such structure was obtained, and the effect of variation of the thickness of the antiferromagnetic layer and the external magnetic field on the frequency of the magnetoelastic resonance was also studied. It was found that an increase in the magnetic field magnitude leads to the increase in the magnetoelastic resonance frequency, and, on the contrary, with an increase in the thickness of the AFM layer the magnitude of the magnetoelastic resonance frequency decreases. The obtained results can be used to develop devices for generating and processing signals in the GHz and THz frequency ranges.

The influence of nonlinearity on the displacement of a singular point in a system of two connected Duffing oscillators when coupling coefficients and insertion losses change. It is shown that the displacement of the singular point when the nonlinearity coefficient changes is accompanied by a decrease in the amplitude of the excited oscillations and a shift in the resonant frequency. The threshold values of the nonlinearity, coupling, and insertion loss coefficients at which a singular point occurs are numerically found. It is shown that an increase in the nonlinearity coefficient leads to a decrease in the threshold value of the insertion losses required for the formation of a singular point.

The results of studying the influence of the thickness of La0.7Sr0.3MnO3 films obtained by magnetron sputtering on (110) NdGaO3 substrates on the magnetic and crystallographic properties using ferromagnetic resonance and X-ray spectroscopy are presented. The dependences of the uniaxial and cubic anisotropy fields on the sample thickness are established. Furthermore, it is shown that the magnetic and crystallographic properties of a film obtained by magnetron sputtering strongly depend on the target region from which it is made. The results obtained will be useful for interpreting the experimental data and creating a series of samples.