We propose a design of a terahertz-frequency signal generator based on a layered structure consisting of a current-driven platinum (Pt) layer and a layer of an antiferromagnet (AFM) with easy-plane ...anisotropy, where the magnetization vectors of the AFM sublattices are canted inside the easy plane by the Dzyaloshinskii-Moriya interaction (DMI). The dc electric current flowing in the Pt layer creates due to the spin Hall effect, a perpendicular spin current that, being injected in the AFM layer, tilts the DMI-canted AFM sublattices out of the easy plane, thus exposing them to the action of a strong internal exchange magnetic field of the AFM. The sublattice magnetizations, along with the small net magnetization vector m(DMI) of the canted AFM, start to rotate about the hard anisotropy axis of the AFM with the terahertz frequency proportional to the injected spin current and the AFM exchange field. The rotation of the small net magnetization mDMI results in the terahertz-frequency dipolar radiation that can be directly received by an adjacent (e.g., dielectric) resonator. We demonstrate theoretically that the radiation frequencies in the range f = 0.05-2 THz are possible at the experimentally reachable magnitudes of the driving current density, and we evaluate the power of the signal radiated into different types of resonators. This power increases with the increase of frequency f, and it can exceed 1 mu W at f similar to 0.5 THz for a typical dielectric resonator of the electric permittivity epsilon similar to 10 and a quality factor Q similar to 750.
The features of the magnetic state of an array of parallel oriented permalloy ribbons are discussed. The arrays are made by explosive lithography. The ribbons have a thickness of 180 nm, a width of ...2.8 µm, and a length of about 4 mm. The distance between ribbons in different samples varies in the range from 300 nm to 4 μm. It is found that the ribbons in the regions far from the end faces are in a single-domain state with small-angle ripples, the magnetization distribution of which correlates with inhomogeneities of the ribbon side surfaces. Moreover, there is a distinct relationship in the spatial distribution of the ripples between adjacent ribbons with a relatively small distance between them. This makes it possible to evaluate the role of the magnetostatic coupling of magnetic subsystems of array elements and to estimate the characteristic value of the random stray field that pins the magnetization.
We review the development trends in microwave magnetism and superconductivity over the last five decades. The review contains the key results of recent studies related to the promising areas of ...modern magnetism and applied physics – spintronics, magnonics, magnon caloritronics, physics of magnonic crystals, spin-wave logic, and the development of novel micro- and nano-scale magnetic devices. The main achievements in these fields of physics are summarized and generalized.
The problem of the frequency spectrum of collective gyrotropic modes in a finite linear chain of magnetostatically interacting ferromagnetic disks has been considered. It has been shown that by ...analyzing the frequency spectrum, one can derive information about the magnetization eddy state for each of the nanodisks in the chain. The feasibility of recording the frequency spectrum as a tool for data readout in magnetic memory devices has been discussed.
We demonstrate theoretically that in a spintronic diode (SD), having a free magnetic layer with perpendicular magnetic anisotropy of the first and second order and no external bias magnetic field, ...the out-of-plane regime of magnetization precession can be excited by sufficiently large (exceeding a certain threshold) RF signals with the frequencies ≲250 MHz. We also show that such a device can operate as a broadband energy harvester capable of converting incident RF power into a DC power with a conversion efficiency of ∼5%. The developed analytical theory of the bias-free SD operation can be used for the optimization of high-efficiency RF detectors and energy harvesters based on SDs.
To test a new approach to gait stereotype correction for patients with central hemiparesis with talipes equinovarus.
The study was performed in a group of patients with formed talipes equinovarus and ...post-stroke hemiparesis. Footwear with orthopaedic elements was offered to the patients. Evaluation of spatial and temporal gait parameters was performed and the risk of falls was assessed.
In the process of work, data were obtained confirming the effectiveness of using specialized shoes for equinovarus foot placement. The risk of falling significantly decreased when walking; walking became more symmetrical due to an increase in the anterior extension of the paretic limb.
Application of this method does not decrease the tone in the paretic limb but optimises the gait stereotype, facilitates the increases of its velocity and decreases the risk of falling.
Abstract Neurorehabilitation of poststroke cognitive impairments is an important medical problem. The purpose of the present study was to estimate the efficacy of new methods of restoration of ...impaired cognitive functions using computer correction programs. 43 poststroke patients aged 57–69, (male — 23, female — 20) were randomized into two groups. First group patients have been treated with the standard methods and supplementary neuropsychological computer training for 14 days, 25–35 min of duration per day. Control group received standard treatment according to Federal and local medical recommendations. Initial and achieved levels of cognitive functioning were estimated with the use of Mini Mental State Examination, Frontal Assessment Battery, the Clock Drawing Test, the Montreal Cognitive Assessment, Schulte's test, Hospital Anxiety and Depression Scale. We found that including the computer correction programs into the complex protocol of rehabilitation of post-stroke patients confirmed their efficacy in both clinical aspects and the Patient Global Impression Scale. Although the results are encouraging, further studies are required with larger samples and longer follow-up to identify characteristics of those patients who are most likely to benefit from computer training of cognitive functions.
The contribution of magnetoelastic effects to the effective magnetic anisotropy of a three-layer film nanodisk (nonmagnetic metal/ferromagnet/nonmagnetic metal) was studied. The mechanical stresses ...at the lateral surface of the disk that are caused by two factors, i.e., unequal thermal expansion of layers and excess surface energy at the layers interfaces, were estimated. The case in which the contribution of magnetoelastic effects to the anisotropy is comparable with those of shape and crystalline anisotropies was discussed. It was shown that the main reason for the change in the local anisotropy field in the vicinity of a nanodisk edge was the mechanical stresses induced by the excess surface energy. The possible application of film nanodisks of nickel with a bilateral golden coating as “nanolancets” for noninvasive cell surgery of tumors was discussed.
Development of the interpretation of the phenomenon of the lift of the magnetic resonance frequencies degeneracy caused by the magnetostatic interaction in assemblies of nanodisks has been done. The ...difference of the resonance behavior of magnetic vortexes in a round and rectangular nanodots has been studied experimentally and explained.
•Development of the interpretation of the phenomenon of the lift of the magnetic resonance frequencies degeneracy caused by the magnetostatic interaction in assemblies of nanodisks has been done.•It is shown that the square nanodots revealed a strong dependence of the resonance frequency on the planar magnetic field.
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