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.

We report the observation of the negative differential resistance (NDR) in the current -driven regime of superconducting MoN / Cu constrictions. Our calculations in framework of time -dependent Ginzburg-Landau equation reveal that in the constriction at large current there is a channel with dynamically suppressed superconducting order parameter along which vortices and antivortices move quasiperiodically over time. As the current increases the constriction switches to the less resistive state with much faster vortices moving periodically over time (quasiphase slip -line state). Microwave radiation experiments demonstrate the presence of Shapiro steps at low voltage, where a slow, time -periodic vortex motion is expected. Conversely, Shapiro steps are absent at high voltage, where the NDR appears, indirectly confirming the quasiperiodic regime.

The technology has been developed for manufacturing the magnetoresistive tunnel junction based on CoFeB/MgO/CoFeB layers with typical lateral sizes in the range from 200 to 700 nm by means of a set of HSQ/PMMA electronic resistive masks. To study the processes of magnetization reversal in the obtained samples, magnetoresistance curves are plotted. It is shown that elements with both vortex and quasi-uniform distributions of free layer magnetization are revealed, which depends on the structure of the magnetosensitive layer and the geometric parameters of the magnetoresistive tunnel junctions. Moreover, the width of the front of magnetization reversal in the elements with quasi-uniform distributions ranges from 2 to 6 Oe.

The technology of manufacturing magnetic tunnel junctions based on CoFeB/MgO/CoFeB layers with characteristic lateral dimensions from 200 to 700 nm using a combination of HSQ/PMMA electronic resistors has been developed. To study the processes of magnetization reversal in the obtained samples, measurements of magnetoresistance curves were carried out. It is shown that, depending on the structure of the magnetically sensitive layer and the geometric parameters of the TMR contacts, elements with both vortex and quasi-homogeneous distribution of the magnetization of the free layer are realized. At the same time, in the latter, the width of the magnetization reversal front is from 2 to 6 Oe.

Hybrid multiferroic films are fabricated by depositing of Pt/Co/Pt multilayers onto [001] and [110] cuts of PMN-PT crystal. The dependence of the interfacial Dzyaloshinskii-Moriya interaction (iDMI) on applied electric field is experimentally investigated in the system by the Brilloin light scattering method. A strong variation (from -0.2 to 0.8 mJ/m2) of the iDMI constant is observed when the electric field is applied. In the case of [001] cut, the observed changes in the iDMI have an isotropic character, while in the case of [110] cut they are anisotropic, which corresponds to the symmetry of the PMN-PT deformations. The change in the iDMI is accompanied by the formation of various unusual domain structures and skyrmion lattices. External control of the DMI with an electric field opens the way to manipulate topological magnetic solitons (such as skyrmions), which are promising objects for information processing and storage.

Co/Pt multilayers with perpendicular magnetic anisotropy were locally irradiated with a focused beam of He+ ions to change the magnetic properties of the sample in strictly defined regions. Irradiated regions of 100-400-nm diameter served as pinning centers for chiral magnetic textures, resulting in the formation of magnetic skyrmions of the same diameter. The magnetization topology of such skyrmions was studied by Lorentz transmission electron microscopy. It was found that the helicity of skyrmions depended on its diameter and the ion irradiation fluence. Both Bloch-type skyrmions and N & eacute;el-type skyrmions, as well as skyrmions of the intermediate type, were observed. We assume that this behavior is due to a change in the balance of the magnetostatic energy and the Dzyaloshinskii-Moriya energy, which is confirmed by micromagnetic simulations.

Silicon nitride membranes were experimentally obtained as substrates for biological samples, which are examined using a microscope with an operating wavelength of 13.8 nm. The free-hanging films obtained have a size of up to 1.5 × 1.5 mm2, which makes it possible to select an area of interest for investigation on the sample on the order of tens to hundreds of microns. The mechanical strength of the membranes satisfies that the samples do not tear the membranes and withstand transportation. The results obtained are an import-substituting technology for the manufacture of Si3N4 membranes. The resulting membranes have a transparency of more than 40

This study explores a Co/Mo-based spintronic THz emitter, demonstrating amplitude modulation by varying the optical pump polarization and applying a +/- 200 kOe magnetic field, achieving up to 70% modulation. (c) 2024 The Author(s)

We present a hybrid spintronic terahertz emitter with a Rashba interface, based on a ferromagnet (Co)/2D semiconductor (WSe2) heterostructure. We demonstrate the potential of such terahertz converters to control amplitude and polarization of terahertz radiation. (C) 2024 The Authors

Rare-earth iron garnet epitaxial films famous for their unique magnetic, microwave and optical properties consistently attract high interest. Domain structure of both bulk and interfaces of garnet films is closely connected with their magnetic properties and magnetization dynamics. In this work, we investigate the magnetic behaviour and domain structure of an epitaxial bismuth-substituted lutetium iron garnet film with a regular array of planar submicron particles made of Co film or Co/Pt multilayer on its surface. Optical polarization microscopy and magnetic force microscopy techniques used for the characterization of these composite structures confirm the mutual influence of the garnet and metal nanostructured layers on each other. On the one hand, dense ordered metal particles provide the pinning of the surface magnetic domains of the garnet film, which further affects the organization of the bulk stripe domains. On the other hand, we observed that the domain structure in the metallic pattern is governed by the domain structure of the garnet placed beneath it.

We have constructed a theory of the Hall effect appearing during the passage of current in a magnetic tunnel junction due to the spin–orbit interaction in an insulator barrier in the approximation of a delta-shaped barrier potential. Both the normal Hall current flowing in metal banks as a result of asymmetric scattering in the tunneling barrier and the anomalous current existing only in the tunneling barrier due to the presence of the spin–orbit interaction in it are taken into account. We have considered the Rashba interaction that can be of intrinsic origin (noncentrosymmetric form of the barrier) or can be induced by an extraneous electric field emerging as a result of application of a potential difference to the barrier. Such a field can reach a value on the order of 109 W/m, which is close to intrinsic atomic fields. The Hall current has both linear and quadratic components in the voltage applied to the tunnel junction. The existence of the nonlinear Hall voltage corresponding to it has been illustrated experimentally in a CoFeB/MgO/Pt tunnel junction, in which the transverse (Hall) voltage has been measured in the Pt layer.

Due to their widely tunable bandgap, HgCdTe heterostructures with quantum wells are a promising material system for semiconductor lasers in the entire mid-infrared range. Recently, Auger-suppressed structures allowed interband stimulated emission (SE) in the atmospheric transparency window 3–5 μm well above 200 K, while previously it was limited to temperatures below 175 K. In contrast to earlier works focused on ridge or vertical emitting HgCdTe lasers, here we demonstrate a whispering gallery mode microdisk (d = 50 μm) laser operating under optical pumping at ∼4 μm in the temperature range attainable by the thermoelectric cooling. Above 200 K, the emission spectrum consists of multiple 0.37-meV-wide peaks associated with the modes of the disk resonator. Laser generation is achieved up to 230 K, which is 40 K lower than the quenching temperature of SE in the unprocessed macroscopic sample. We associate the difference with the optical losses introduced by the inclined walls of the disk.

Transport characteristics of superconducting MoN strips with a single side cut near one of the superconductor edges in zero and weak magnetic fields are studied experimentally and theoretically. The presence of the cut makes it possible to observe regimes with one and several simultaneously moving Abrikosov vortices, the number of which is controlled by the value of the applied current. A change in the number of vortices is accompanied with the emergence of a “kink” on the current–voltage characteristic, which can be clearly distinguished in the dependence of the differential resistance on the current. This makes it possible to find average velocityv¯of vortices (including a single vortex) and the current/voltage ranges with the known number of moving vortices. The vortex velocity determined in this way for our superconducting strips turns out to be weakly depending on the current and is close to maximal valuev¯max≈ 3 km/s, for which a superconductor transition to the normal state occurs. The maximal velocity value is comparable with the known values for superconductors of types Nb, NbN as well as, and YBCO, but is several times smaller than for superconductors of types MoSi, NbC, and Pb. The fact that difference in the maximal velocities of vortices is associated with different times of variation of the superconducting order parameter magnitude in different superconducting materials is considered.

An Erratum to this paper has been published: https://doi.org/10.1134/S1063776123110171

We propose a method for calibration of magnetic field in the objective lens of transmission electron microscope. The calibration process is based on classical Fresnel imaging of Permalloy disks and measuring the displacement of the magnetic vortex core when the sample is tilted at various excitations of the objective lens. We adopted the Carl Zeiss LIBRA 200 MC transmission electron microscope for Lorentz electron microscopy using this method. The objective lens magnetic field evaluation is tested on the Co/Pt multilayered films with known magnetic properties.

We have constructed a theory of the Hall effect appearing during the passage of current in a magnetic tunnel junction due to the spin–orbit interaction in an insulator barrier in the approximation of a delta-shaped barrier potential. Both the normal Hall current flowing in metal banks as a result of asymmetric scattering in the tunneling barrier and the anomalous current existing only in the tunneling barrier due to the presence of the spin–orbit interaction in it are taken into account. We have considered the Rashba interaction that can be of intrinsic origin (noncentrosymmetric form of the barrier) or can be induced by an extraneous electric field emerging as a result of application of a potential difference to the barrier. Such a field can reach a value on the order of 10 9 W/m, which is close to intrinsic atomic fields. The Hall current has both linear and quadratic components in the voltage applied to the tunnel junction. The existence of the nonlinear Hall voltage corresponding to it has been illustrated experimentally in a CoFeB/MgO/Pt tunnel junction, in which the transverse (Hall) voltage has been measured in the Pt layer.

The results of systematic experimental studies of the magnetic state and crystal structure of multilayer films based on a ferromagnet/heavy metal pair (Co/Pt) by optical magnetometry, magnetic force microscopy, Lorentz and analytical transmission electron microscopy are presented. It is shown that with an increase in the number of Co/Pt periods in the films, an increase in the average size of crystal grains is observed, which leads to an increase in the dispersion of perpendicular anisotropy and, as a consequence, to a decrease in the size of magnetic domains and magnetization reversal fields. In addition, in films with n≥6 periods, the domain wall becomes hybrid; has an intermediate structure between the walls of the Neel and Bloch types.

The paper reports on laser-induced Bragg resonances in the spectrum of magnetostatic waves in a heterostructure based on a ferrite film [yttrium iron garnet (YIG)] with periodic strips of semiconductor material (Si) on the surface. Laser irradiation of such a structure leads to the formation of Bragg bandgaps due to the modulation of the Si conductivity on the YIG surface, and the magnitude modulation increases with increasing laser radiation intensity. It is shown that an increase in laser radiation intensity also leads to an increase in the depth and frequency shift of the bandgaps.

We report on the design of a spintronic emitter based on the Pt(3 nm)/Co(3 nm) structure, which enables the control over terahertz radiation polarization. Utilizing the field-induced magnetization rotation that takes place at low magnetic fields of up to 250 Oe at room temperature, we have achieved the full range of terahertz polarization rotation from 0° to 360°. This rotation became possible due to the uniaxial magnetic anisotropy induced in the plane of the cobalt film during its fabrication. We evaluated the efficiency of the Co/Pt structure in generating terahertz radiation and found that the terahertz pulse energy flux reaches ∼160 nJ/cm2 at an excitation flux of 4 mJ/cm2.

Normally in superconductors, as in conductors, in the state with zero current $I$ the momentum of superconducting electrons $\hbar q =0$. Here we demonstrate theoretically and present experimental evidences that in superconducting/normal metal (SN) hybrid strip placed in in-plane magnetic field $B_{in}$ finite momentum state ($\hbar q \neq 0$) is realized when $I=0$. This state is characterized by current-momentum dependence $I(q)\neq -I(-q)$, nonreciprocal kinetic inductance $L_k(I) \neq L_k(-I)$ and different values of depairing currents $I_{dep}^{\pm}$ flowing along the SN strip in opposite directions. Found properties have {\it orbital} nature and are originated from gradient of density of superconducting electrons $\nabla n$ across the thickness of SN strip and field induced Meissner currents. We argue that this type of finite momentum state should be rather general phenomena in superconducting structures with artificial or intrinsic inhomogeneities.