The influence of a large spin-polarized current on the coupled dynamics of vortices in spin-transfer nanooscillators with a diameter of 400 nm is investigated. New stationary modes of coupled oscillations of vortices have been discovered, both for the same and opposite polarities of their cores. The dependence of the frequency of stationary coupled oscillations of magnetic vortices on the magnitude of the spin-polarized current has been studied. The found effect can be used to increase the operating frequencies of spin-transfer nano-oscillators.

The paper presents a theoretical analysis of magnetization switching in a gadolinium ferrite garnet film due to the demagnetizing effect of a femtosecond laser pulse. Using the Lagrange formalism for a two-sublattice ferrimagnet, the effective Lagrangian, thermodynamic potential, and Rayleigh dissipative function are obtained. The phase diagram of the ferrite film is analyzed, and the main states of the system are identified. Magnetization switching diagrams and trajectories of the order parameter dynamics of the magnet are constructed. The ranges of magnetic fields, temperatures, and demagnetization values for the most efficient magnetization switching are analyzed.

The interaction of light with spins in a Heisenberg antiferromagnet with a negligibly low magnetic anisotropy as in RbMnF3 has been theoretically analyzed. In particular, an optical pump–probe experiment, where coherent terahertz magnons are excited by short pump laser pulses in the antiferromagnet and are then detected by a probe pulse delayed with respect to the pump pulse, has been simulated. It has been shown that the giant increase in the intensity of excitation of terahertz magnons under the influence of the inverse Cotton–Mouton effect occurs near parametric resonance, i.e., in the parametric instability region.

Applied interest to spintronics devices based on magnetic tunnel junction (MTJ) is motivated mainly by low power consumption and high density. To co-design hybrid spintronic-electronic circuits within the general CMOS design flow, we present behavioral compact model of MTJ in Verilog-A language, compatible with computer-aided design (CAD) systems and scalable to different technological nodes. The compact model simulates the magnetization dynamics as a function of the external field, device anisotropy, magnetostatic field, spin-transfer torque (STT) included shot and Nyquist currents, thermal induced fields. Predictive abilities of model were confirmed experimentally by comparison to the measurements of magnetoresistance and spin-torque ferromagnetic resonance (ST-FMR) on the MTJ sample with a diameter of 100 nm. The model parameters were approximated by data obtained from the magnetoresistance measurements. These estimated parameters were subsequently utilized in a circuit simulator Cadence Spectre for prediction of the ST-FMR outcomes. Results of compact simulation and experiment have qualitative and quantitative agreement.

The solid thin films of Py/Pt and Py/W heterostructures have been studied using the ferromagnetic resonance method. The temperature dependences of the Gilbert damping parameter and voltage of the inverse spin Hall effect (ISHE) have been obtained in the 5–290 K temperature range. An abnormal increase in the Gilbert damping parameter in the vicinity of 50 K and a change in the voltage of ISHE has been found. It has been concluded that an increase in the Gilbert damping parameter is of spin-orbital nature.

Spin-transfer ferromagnetic resonance in a planar external magnetic field is used to perform an experimental study of the effect produced by broadband rectification of a microwave current in magnetic tunnel junctions with perpendicular magnetic anisotropy. It is found that the parameters of broadband rectification (frequency range, rectified voltage, and the region of the mode of ferromagnetic resonance) depend on the size and its shape of the sample. The maximum rectified voltage is observed on a round elliptical sample of 100 × 150 nm. At the same time, the widest operating frequency range of approximately 2 GHz was observed on strongly elliptical MTJs with sizes of 75 × 250 nm2.

A theoretical model is proposed for calculating the H‒T phase diagrams of a rare-earth ferrimagnet. The model considers the effects of each magnetic sublattice and the induced surface anisotropy. The magnetic phase diagrams are calculated numerically. Surface anisotropy blurs the lines of the second-order phase transition between the collinear and angular phases, the displacement of the tricritical point, and the possible formation of new phase transition lines.

Structures of the heavy metal/ferromagnetic type are of great interest since magnetization can be switched in them due to the transfer of the spin torque by the spin-orbit interaction mechanism. This type of switching has advantages for the applications in magnetoresistive memory cells. Employing this mechanism, the memory cells can have a simple structure, and the magnetization switching requires less energy than in the case of direct spin torque transfer. We have studied a sample of MgO/CoFeB/Ta with in-plane magnetization and high spin polarization. In this work, the Hall adiabatic harmonic voltage method is used to study the effective damping coefficient, as well as to estimate the values of the effective fields that arise in such structures due to the spin-polarized current.

Broadband voltage rectification is an interesting effect that was recently discovered in magnetic tunnel junction (MTJ) structures. Usually, this effect occurs for certain types of MTJ structures and for special configurations of the external magnetic field (namely, perpendicular to the plane component of magnetization). We report on an alternative type of broadband rectification effect with a frequency range up to 6 GHz that is observed in MTJ samples with in-plane magnetization and without an external out-of-plane magnetic field. We compare the experimental study with numerical calculations and theoretical analysis to explain the results. Furthermore, we demonstrated that for the appearance of broadband rectification, it is sufficient to create a nonzero equilibrium angle between the polarizer and the free layer. Our work paves the way for improved energy efficiency in wireless microwave energy-harvesting applications.

The heavy metal/ferromagnet type MgO/CoFeB/Ta structure with in-plane magnetization and high spin polarization was studied. We use the adiabatic harmonic Hall voltage method to study the effective damping coefficient and to estimate the values of the effective fields that arise in such structures under the action of a spin-polarized current.

In this work we studied the auto-oscillation mode of structures based on magnetic tunnel junctions. During the experiment we studied how different values and orientation of the magnetic field affect the efficiency of the auto-oscillations regime for samples of various shapes. The auto-oscillation mode in samples was observed near the transition from one state of magnetization of the free layer to another. It was found that the maximum value of the power spectral density and its position relative to the frequency axis can be controlled by changing the magnitude and orientation of the external magnetic field. Keywords: Magnetic tunnel junction (MTJ), auto-oscillations, power spectral density, nanooscillator.

The development of new computing technologies has given a new stimulus in the study of multiferroics. The use of multiferroics allows the realization of competitive energy efficient scalable logic and storage devices. The low-power consumption in Magneto Electric-Spin Orbital logics and Magnetic Random Access Memory components is provided by magnetoelectric switching in multiferroic based systems using a low-energy electric field. Our work concerns the modelling of the Magneto Electric-Spin Orbital elements with an emphasis on the magnetoelectric component and simulation of magnetization reversal processes in a model system. The use of the proposed approach makes it possible to analyze the influence of dimensional factors (film thicknesses, transverse dimensions, sample shape) affecting the magnetic states of multiferroic nanoelements; taking into interfacial interactions (magnetic anisotropy and interlayer exchange); energy-efficient external influences that allow switching magnetic states using magnetic and electric fields.

In this work we studied the auto-oscillation mode of structures based on magnetic tunnel junctions. During the experiment we studied how different values and orientation of the magnetic field affect the efficiency of the self-generation regime for samples of various shapes. The auto-oscillation mode in samples was observed near the transition from one state of magnetization of the free layer to another. It was found that the maximum value of the power spectral density and its position relative to the frequency axis can be controlled by changing the magnitude and orientation of the external magnetic field.

We present the investigation of the behavior of magnetic tunnel junction’s (MTJ) modes for the different magnitude and the directions of the external magnetic field by the ST-FMR method. We have found an insensitive mode of MTJ to the direction of the external magnetic field. Using macrospin modeling, we show that the behavior of the uniform mode of a free layer of MTJ is like the insensitive mode.

The magnetoelectricity of samarium iron garnet is theoretically investigated: the antiferroelectric structures of samarium ions are described and their connection with the configurations of the magnetic moments of the ions and their transformations during magnetic phase transitions is revealed. The possibility of the appearance at low temperatures of unusual Bloch domain walls, in which the magnetization vector rotates from the [u v 0] axes to the [v u 0] axes, which are not crystal symmetry axes, is established. The electric polarization of Bloch domain walls, which are realized both at low (T0 K) and high temperatures, is studied. It has been established that the electric polarization of Bloch boundaries, which arises because of an inhomogeneous magnetoelectric effect, depends significantly on their shape. Keywords: rare-earth iron garnets, magnetic phase transitions, Bloch domain walls, inhomogeneous magnetoelectric effect.

An experimental study is performed of the effect the value and direction of an external magnetic field has on the magnetization of a free layer in magnetic tunnel junctions 100, 150, and 250 nm in diameter. Two free layer modes are found in samples with a diameter of 100 nm. The first mode is less sensitive to the value and direction of the external magnetic field than the second, which is shifted in the frequency domain. Nonuniform magnetization of the free layer in weak fields is observed upon an increase in the geometric size of the magnetic tunnel junctions, and a mode insensitive to the direction of the external magnetic field is identified. A macrospin model is obtained of the behavior of the homogeneous mode of a free layer’s shape (disk or ellipse) at a constant value and different directions of the external magnetic field.

Electrical model of a magnetic tunnel junction is developed in Verilog-A language, which can use in CAD systems to design an integrated circuit of spintronics devices. In order to check the correct operation of the model verification tests were created and carried out in Cadence ADE. Each test corresponds to the operating mode of the magnetic tunnel junction: switching, generation, rectification. Thus, the developed model can be used to simulate hybrid circuits comprising CMOS elements and magnetic tunnel junctions. Keywords: magnetic tunnel junction, MTJ, spintronics, spintronics devices, magnetic tunnel junction model in Verilog-A, MTJ model development, MTJ operating modes.

Vortex spin torque nano-oscillators (STNOs) are multilayer spin-valve magnetic nanopillars, in which the magnetic layers (one or both) contain a magnetic vortex, the dynamics of which provides microwave radiation. In vortex STNOs, it was possible to achieve a high microwave signal power (on the order of 1 μW) and a relatively narrow linewidth (several hundreds of kHz). To further increase the power and improve the spectral characteristics of vortex STNOs, the collective dynamics and synchronization conditions in the ensembles of such nanostructures are studied. The subject of this review is the latest achievements in the field of physics and technology of vortex STNOs.

We present a powerful method to detect the magnetic domain wall (DW), based on the intrinsic characteristic of anomalous Hall effect (AHE), by employing magneto-transport measurement on a device of double Hall cross geometry. We demonstrate that DW propagation manifests its behavior in the distinctive AHE hysteresis and longitudinal magnetoresistance (MR). As DW propagates along the Hall channel, the AHE hysteresis varies considerably depending on the voltage-pickup position while MR displays abnormal asymmetric peaks. Utilizing this direct correlation, we formulate simple models for AHE switching path and MR peak so that they can be efficiently used to characterize DW behavior. It is revealed that at the nucleation stage, the DW velocity grows exponentially with respect to the field. Additionally, the effects of magnetic pinning sites are taken into account and shed light on. The proposed method could be potentially employed for the detection of DW behavior in nanoscale devices.

A spin torque nano-oscillator in the form of a three-layer magnetic tunneling junction of small diameter (120 nm), where the magnetizations in both magnetic layers are in vortex state, is considered. The effect of the thickness of a nonmagnetic layer on the coupled dynamics of two magnetic vortices in a spin torque nano-oscillator has been studied. The thick permalloy magnetic layer has a thickness of 15 nm, the middle non-magnetic layer has a thickness in the first case of 12.5 and in the second 15 nm, and the thin permalloy magnetic layer has a thickness of 4 nm. Numerical calculation of the dynamics of magnetostatically coupled vortices was carried out using the software package SpinPM for micromagnetic modeling. The features of the vortex motion dynamic are studied for different thicknesses of the nonmagnetic interlayer. It is shown that in all cases of thickness of the nonmagnetic interlayer, three regimes of vortex dynamics are observed: the oscillations of magnetic vortices damped over time, the mode of stationary coupled oscillations of magnetic vortices, and regime, when vortices “leave” the edge of the disk. It is found that increasing in the thickness of the nonmagnetic layer leads to decreasing in the values of the first, second, and third critical currents.