Resonant generation of propagating second-harmonic spin waves in nano-waveguides.

Generation of second-harmonic waves is one of the universal nonlinear phenomena that have found numerous technical applications in many modern technologies, in particular, in photonics. This phenomenon also has great potential in the field of magnonics, which considers the use of spin waves in magnetic nanostructures to implement wave-based signal processing and computing. However, due to the strong frequency dependence of the phase velocity of spin waves, resonant phase-matched generation of second-harmonic spin waves has not yet been achieved in practice. Here, we show experimentally that such a process can be realized using a combination of different modes of nano-sized spin-wave waveguides based on low-damping magnetic insulators. We demonstrate that our approach enables efficient spatially-extended energy transfer between interacting waves, which can be controlled by the intensity of the initial wave and the static magnetic field.

True amplification of spin waves in magnonic nano-waveguides.

Magnonic nano-devices exploit magnons - quanta of spin waves - to transmit and process information within a single integrated platform that has the potential to outperform traditional semiconductor-based electronics. The main missing cornerstone of this information nanotechnology is an efficient scheme for the amplification of propagating spin waves. The recent discovery of spin-orbit torque provided an elegant mechanism for propagation losses compensation. While partial compensation of the spin-wave losses has been achieved, true amplification - the exponential increase in the spin-wave intensity during propagation - has so far remained elusive. Here we evidence the operating conditions to achieve unambiguous amplification using clocked nanoseconds-long spin-orbit torque pulses in magnonic nano-waveguides, where the effective magnetization has been engineered to be close to zero to suppress the detrimental magnon scattering. We achieve an exponential increase in the intensity of propagating spin waves up to 500% at a propagation distance of several micrometers.

Giant nonlinear self-phase modulation of large-amplitude spin waves in microscopic YIG waveguides.

Nonlinear self-phase modulation is a universal phenomenon responsible, for example, for the formation of propagating dynamic solitons. It has been reported for waves of different physical nature. However its direct experimental observation for spin waves has been challenging. Here we show that exceptionally strong phase modulation can be achieved for spin waves in microscopic waveguides fabricated from nanometer-thick films of magnetic insulator, which support propagation of spin waves with large amplitudes corresponding to angles of magnetization precession exceeding 10°. At these amplitudes, the nonstationary nonlinear dynamic response of the spin system causes an extreme broadening of the spectrum of spin-wave pulses resulting in a strong spatial variation of the spin-wave wavelength and a temporal variation of the spin-wave phase across the pulse. Our findings demonstrate great complexity of nonlinear wave processes in microscopic magnetic structures and importance of their understanding for technical applications of spin waves in integrated devices.

Evidence for spin current driven Bose-Einstein condensation of magnons.

The quanta of magnetic excitations - magnons - are known for their unique ability to undergo Bose-Einstein condensation at room temperature. This fascinating phenomenon reveals itself as a spontaneous formation of a coherent state under the influence of incoherent stimuli. Spin currents have been predicted to offer electronic control of Bose-Einstein condensates, but this phenomenon has not been experimentally evidenced up to now. Here we show that current-driven Bose-Einstein condensation can be achieved in nanometer-thick films of magnetic insulators with tailored nonlinearities and minimized magnon interactions. We demonstrate that, above a certain threshold, magnons injected by the spin current overpopulate the lowest-energy level forming a highly coherent spatially extended state. We quantify the chemical potential of the driven magnon gas and show that, at the critical current, it reaches the energy of the lowest magnon level. Our results pave the way for implementation of integrated microscopic quantum magnonic and spintronic devices.

[Molecular and clinical aspects of the effect of cytidyndiphosphocholine on cognitive functions]. / Molekulyarnye i klinicheskie aspekty deistviya tsitidindifosfokholina na kognitivnye funktsii.

OBJECTIVE: Systematization of the array of publications on cytidyldiphosphocholine (CDP-choline). MATERIAL AND METHODS: Systematic computer analysis of all currently available publications on CDP-choline (1750 publications in PUBMED) using the topological theory of big data analysis. RESULTS: CDP-choline is essential for acetylcholine biosynthesis, phospholipid metabolism, and DNA methylation. The article describes the effects of CDP-choline on acetylcholinergic and other types of neurotransmission, anti-inflammatory, neuroprotective and neurotrophic effects of CDP-choline. Also, the paper presents the effects of the molecule on lipid metabolism and gene expression within the post-genomic paradigm (in particular, an increase in the expression of nicotinic and muscarinic acetylcholine receptors). The results of fundamental and clinical studies of CDP-choline in the treatment of cognitive impairments associated with cerebral ischemia and neurodegeneration are presented. CONCLUSION: The pharmacological effects of CDP-choline are mediated through multiple molecular mechanisms that contribute to the nootropic action of this molecule.

Ion-temperature determination with a baffled Langmuir probe.

An electrostatic Langmuir probe for real-time measurements of parameters in magnetized plasma is tested in fully ionized, barium, Q-machine plasma. The small-diameter, long-length, tungsten wire sensor, i.e., the probe tip, oriented with its cylindrical axis perpendicular to the magnetic field (B), is partially shielded by ceramic baffles, or masks, that form sensor-access slots between the baffles. Adjusting the azimuthal orientation of the slots, by rotating the probe about its cylindrical axis, changes the fraction of proximity gyro-orbiting electrons, relative to the fraction of proximity gyro-orbiting ions, that can access the recessed sensor along the magnetic field. Thus, the ratio between the electron and ion saturation currents, Ie sat and Ii sat, can be adjusted without having affected the probe bias voltage Vb. When optimally shielded (Ie sat/Ii sat=1), accurate, real-time measurements of space potential Vs can be acquired. When maximally shielded (Ie sat/Ii sat≪1), accurate, real-time measurements of ion temperature Ti can be acquired. Subtracting the floating potential Vf of an optimally shielded baffled probe from Vf of a maximally shielded baffled probe yields Ti (and its fluctuation phase) in real time.

The 2021 Magnonics Roadmap.

Magnonics is a budding research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. The rapid advancements of this field during last one decade in terms of upsurge in research papers, review articles, citations, proposals of devices as well as introduction of new sub-topics prompted us to present the first roadmap on magnonics. This is a collection of 22 sections written by leading experts in this field who review and discuss the current status besides presenting their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and its interconnections to standard electronics. To this end, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This roadmap asserts a milestone for future emerging research directions in magnonics, and hopefully, it will inspire a series of exciting new articles on the same topic in the coming years.

Spatial separation of degenerate components of magnon Bose-Einstein condensate by using a local acceleration potential.

Bose-Einstein condensation (BEC) of magnons is one of the few macroscopic quantum phenomena observable at room temperature. Due to the competition of the exchange and the magnetic dipole interactions, the minimum-energy magnon state is doubly degenerate and corresponds to two antiparallel non-zero wavevectors. Correspondingly, the room-temperature magnon BEC differs essentially from other condensates, since it takes place simultaneously at ± kmin. The degeneracy of BEC and interaction between its two components have significant impact on condensate properties. Phase locking of the two condensates causes formation of a standing wave of the condensate density and quantized vortices. Additionally, interaction between the two components is believed to be important for stabilization of the condensate with respect to a real-space collapse. Thus, the possibility to create a non-degenerate, single-component condensate is decisive for understanding of underlying physics of magnon BEC. Here, we experimentally demonstrate an approach, which allows one to accomplish this challenging task. We show that this can be achieved by using a separation of the two components of the degenerate condensate in the real space by applying a local pulsed magnetic field, which causes their motion in the opposite directions. Thus, after a certain delay, the two clouds corresponding to different components become well separated in the real space. We find that motion of the clouds can be described well based on the peculiarities of magnon dispersion characteristics. Additionally, we show that, during the motion, the condensate cloud harvests non-condensed magnons, which results in a partial compensation of condensate depletion.

Direct evidence of spatial stability of Bose-Einstein condensate of magnons.

Bose-Einstein condensation of magnons is one of few macroscopic quantum phenomena observed at room temperature. Since its discovery, it became an object of intense research, which led to the observation of many exciting phenomena such as quantized vortices, second sound, and Bogolyubov waves. However, it remained unclear what physical mechanisms can be responsible for the spatial stability of the magnon condensate. Indeed, since magnons are believed to exhibit attractive interaction, it is generally expected that the condensate is unstable with respect to the real-space collapse, contrarily to experimental findings. Here, we provide direct experimental evidence that magnons in a condensate exhibit repulsive interaction resulting in the condensate stabilization and propose a mechanism, which is responsible for this interaction. Our experimental conclusions are additionally supported by the theoretical model based on the Gross-Pitaevskii equation. Our findings solve a long-standing problem, providing a new insight into the physics of magnon Bose-Einstein condensates.

Excitation of coherent second sound waves in a dense magnon gas.

Second sound is a quantum mechanical effect manifesting itself as a wave-like (in contrast with diffusion) heat transfer, or energy propagation, in a gas of quasi-particles. So far, this phenomenon has been observed only in an equilibrium gas of phonons existing in liquid/solid helium, or in dielectric crystals (Bi, NaF) at low temperatures. Here, we report observation of a room-temperature magnonic second sound, or a wave-like transport of both energy and spin angular momentum, in a quasi-equilibrium gas of magnons undergoing Bose-Einstein condensation (BEC) in a ferrite film. Due to the contact of the magnon gas with pumping photons and phonons, dispersion of the magnonic second sound differ qualitatively from the phononic case, as there is no diffusion regime, and the second sound velocity remains finite at low wavenumbers. Formation of BEC in the gas of magnons modifies the second sound properties by creating an additional channel of energy relaxation.

Spin Hall-induced auto-oscillations in ultrathin YIG grown on Pt.

We experimentally study nanowire-shaped spin-Hall nano-oscillators based on nanometer-thick epitaxial films of Yttrium Iron Garnet grown on top of a layer of Pt. We show that, although these films are characterized by significantly larger magnetic damping in comparison with the films grown directly on Gadolinium Gallium Garnet, they allow one to achieve spin current-driven auto-oscillations at comparable current densities, which can be an indication of the better transparency of the interface to the spin current. These observations suggest a route for improvement of the flexibility of insulator-based spintronic devices and their compatibility with semiconductor technology.

Chemical potential of quasi-equilibrium magnon gas driven by pure spin current.

Pure spin currents provide the possibility to control the magnetization state of conducting and insulating magnetic materials. They allow one to increase or reduce the density of magnons, and achieve coherent dynamic states of magnetization reminiscent of the Bose-Einstein condensation. However, until now there was no direct evidence that the state of the magnon gas subjected to spin current can be treated thermodynamically. Here, we show experimentally that the spin current generated by the spin-Hall effect drives the magnon gas into a quasi-equilibrium state that can be described by the Bose-Einstein statistics. The magnon population function is characterized either by an increased effective chemical potential or by a reduced effective temperature, depending on the spin current polarization. In the former case, the chemical potential can closely approach, at large driving currents, the lowest-energy magnon state, indicating the possibility of spin current-driven Bose-Einstein condensation.

[An experimental study of anticonvulsant effects of myo-inositol and folic acid]. / Protivosudorozhnye effekty mio-inozitola v sochetanii s folievoi kislotoi v eksperimente.

AIM: To study the micronutrients that potentiate the action of anticonvulsant drugs, and in particular, of myo-inositol (vitamin B8). MATERIAL AND METHODS: An experimental study of neurotrophic and anticonvulsant effects of a preparation based on myo-inositol (inofert) on thiosemicarbazide models of seizures was carried out. RESULTS: Inofert significantly increased the latent time before the first convulsive seizure, reduced the severity of seizures (p<0.05) and reduced mortality in the models of thiosemicarbazide seizures. Myo-inositol enhanced anticonvulsant action of gabapentin and sodium valproate; neuroprotective effect of myo-inositol was also confirmed. CONCLUSION: The Inofert preparation, containing myo-inositol and folic acid, modulates the effects of drugs with both convulsive and anticonvulsive action, reduces the severity and duration of seizures caused by thiosemicarbazide and increases the survival rate of animals.

Direct observation of dynamic modes excited in a magnetic insulator by pure spin current.

Excitation of magnetization dynamics by pure spin currents has been recently recognized as an enabling mechanism for spintronics and magnonics, which allows implementation of spin-torque devices based on low-damping insulating magnetic materials. Here we report the first spatially-resolved study of the dynamic modes excited by pure spin current in nanometer-thick microscopic insulating Yttrium Iron Garnet disks. We show that these modes exhibit nonlinear self-broadening preventing the formation of the self-localized magnetic bullet, which plays a crucial role in the stabilization of the single-mode magnetization oscillations in all-metallic systems. This peculiarity associated with the efficient nonlinear mode coupling in low-damping materials can be among the main factors governing the interaction of pure spin currents with the dynamic magnetization in high-quality magnetic insulators.

[Neurotrophic peptides of сerebrolysin as a basis for anticonvulsant effect of the drug]. / Neirotroficheskie peptidy tserebrolizina kak osnova protivosudorozhnogo potentsiala preparata.

AIM: To study an effect of cerebrolysin on the expression and severity of primary-generalized seizures caused by thiosemicarbazide and to analyze the corresponding molecular mechanisms. MATERIAL AND METHODS: The effects of cerebrolysin were studied on the thiosemicarbazide model of convulsions in 144 male rats. Cerebrolysin was introduced intraperitoneally in the dose of 2.5 ml/kg of body mass 5 days a week during 18 days. RESULTS AND CONCLUSION: Cerebrolysin reduces the severity and duration of seizures caused by thiosemicarbazide and increases the survival rate of animals. Cerebrolysin potentiates the anticonvulsant action of gabapentin and sodium valproate. Neurohistological analysis has shown that the thiosemicarbazide model results in the ischemic brain damage. Cerebrolysin substantially minimizes the ischemic injury of neurocytes induced by thiosemicarbazide and contributes to the restoration of brain tissue morphology.

Generation of coherent spin-wave modes in yttrium iron garnet microdiscs by spin-orbit torque.

In recent years, spin-orbit effects have been widely used to produce and detect spin currents in spintronic devices. The peculiar symmetry of the spin Hall effect allows creation of a spin accumulation at the interface between a metal with strong spin-orbit interaction and a magnetic insulator, which can lead to a net pure spin current flowing from the metal into the insulator. This spin current applies a torque on the magnetization, which can eventually be driven into steady motion. Tailoring this experiment on extended films has proven to be elusive, probably due to mode competition. This requires the reduction of both the thickness and lateral size to reach full damping compensation. Here we show clear evidence of coherent spin-orbit torque-induced auto-oscillation in micron-sized yttrium iron garnet discs of thickness 20 nm. Our results emphasize the key role of quasi-degenerate spin-wave modes, which increase the threshold current.

[Evaluation of the antitumor potential of cerebrolysin]. / Otsenka protivoopukholevogo potentsiala tserebrolizina.

AIM: To investigate the effect of cerebrolysin on the growth and metastasis of malignant tumors in mice (a model of lung carcinoma Lewis). MATERIAL AND METHODS: The study was performed on 60 male mice, hybrids F1 (the age of 2-2.5 months, body weight 19-22g.). Transplantable epidermoid Lewis lung carcinoma (LLC) was used as a standard experimental model to evaluate the properties of the potential antitumor agents. Experimental animals were administered a single intraperitoneal injection of cerebrolysin in doses of 524 mg/kg (n=20) and 1800 mg/kg (n=20) daily from 2 to 16 days after tumor transplantation. RESULTS AND CONCLUSION: Compared with the control group (n=20), cerebrolysin induced growth inhibition of LLC during the treatment (7 to 16 days). An impact of the drug was accompanied by the inhibition of the tumor growth rate by 10-15% (p<0.05). Cerebrolysin demonstrated a dose-dependent effect of reducing the large number of metastases: a number of large metastases significantly decreased by 30-50% with the increase of cerebrolysin dose (p=0.01). Cerebrolysin can significantly suppress the growth rate of Lewis lung carcinoma.

[Ecological and physiological assessment of the elemental status in the adult population of the Republic of Bashkortostan].

The study of elemental status was carried out as a result of a multielement analysis of hair by ICP-MS within the framework of the Federal Program "National System of chemical and biological security of the Russian Federation, 2009-2014". This parameter is an index of the impact of the environment on the body. A total of 1,138 adult residents of the Republic of Bashkortostan (624 women and 514 men aged of25-50 years) were examined. The features of the element status of the adult population of the Republic were shown. The obtained data can be used as reference values of chemical elements in the hair of the adult population of the Republic of Bashkortostan.

[INFLUENCE OF NITRIC OXIDE AND ALPHA-TOCOPHEROL ON STRUCTURAL CHANGES IN PLACENTA DURING VIOLATION OF UTEROPLACENTAL CIRCULATION IN WHITE RATS].

We have studied the effect of nitric oxide and alpha-tocopherol on morphological changes in the placenta of white rats during pregnancy complicated by disorders of the uterine and placental circulation. Violation of the uteroplacental circulation was reproduced by the method of M. M. Vartanova (1984). In white rats with violated uteroplacental blood circulation, the use of L-arginine methyl ester compensates for disturbances of the fetoplacental blood flow. It is established that an increase in nitric oxide and the inhibition of free radical processes in the placenta of experimental animals under conditions of artificially created pathology of pregnancy belong to pathogenetic rather than sanogenetic factors.

[Pharmacokinetic and pharmacodynamic synergism between neuropeptides and lithium in the neurotrophic and neuroprotective action of cerebrolysin].

OBJECTIVE: To study the synergism between neuropeptides and lithium ions. MATERIAL AND METHODS: An experimental model of stroke (chronic bilateral occlusion of the common carotid arteries in rats), neuronal culture studies, histomorphological analyses, determination of micronutrient profile of brain substrates were used. RESULTS: A complex of experimental studies revealed that the effect of cerebrolysin is influenced by the synergism between lithium ions and the neuropeptide contentof this drug. Pharmacokinetic synergism promotes the accumulation of lithium in brain tissues during cerebrolysin treatment. The existence of the pharmacokinetic synergism is evident from the potentiation of neuroprotective effects of the drug under the action of lithium ions established in the model of stroke. CONCLUSION: Lithium ions potentiate neuroprotective effects of cerebrolysin.