arXiv subjects

A. Sukhov

Publications and source records attributed to A. Sukhov.

At least 19 recordsLinked to original sources

arXiv2023

Classification of networks-on-chip in the context of analysis of promising self-organizing routing algorithms

This paper contains a detailed analysis of the current state of the network-on-chip (NoC) research field, based on which the authors propose the new NoC classification that is more complete in comparison with previous ones. The state of the domain associated with wireless NoC is investigated, as the transition to these NoCs reduces latency. There is an assumption that routing algorithms from classical network theory may demonstrate high performance. So, in this article, the possibility of the usage of self-organizing algorithms in a wireless NoC is also provided. This approach has a lot of advantages described in the paper. The results of the research can be useful for developers and NoC manufacturers as specific recommendations, algorithms, programs, and models for the organization of the production and technological process.

cs.NI↗

arXiv2023

Lattice Boltzmann simulations of two linear microswimmers using the immersed boundary method

The performance of a single or the collection of microswimmers strongly depends on the hydrodynamic coupling among their constituents and themselves. We present a numerical study for a single and a pair of microswimmers based on lattice Boltzmann method (LBM) simulations. Our numerical algorithm consists of two separable parts. Lagrange polynomials provide a discretization of the microswimmers and the lattice Boltzmann method captures the dynamics of the surrounding fluid. The two components couple via an immersed boundary method. We present data for a single swimmer system and our data also show the onset of collective effects and, in particular, an overall velocity increment of clusters of swimmers.

cond-mat.soft↗

arXiv2018

Magnetophononics: ultrafast spin control through the lattice

Using a combination of first-principles and magnetization-dynamics calculations, we study the effect of the intense optical excitation of phonons on the magnetic behavior in insulating magnetic materials. Taking the prototypical magnetoelectric \CrO\ as our model system, we show that excitation of a polar mode at 17 THz causes a pronounced modification of the magnetic exchange interactions through a change in the average Cr-Cr distance. In particular, the quasi-static deformation induced by nonlinear phononic coupling yields a structure with a modified magnetic state, which persists for the duration of the phonon excitation. In addition, our time-dependent magnetization dynamics computations show that systematic modulation of the magnetic exchange interaction by the phonon excitation modifies the magnetization dynamics. This temporal modulation of the magnetic exchange interaction strengths using phonons provides a new route to creating non-equilibrium magnetic states and suggests new avenues for fast manipulation of spin arrangements and dynamics.

cond-mat.str-el↗

arXiv2018

Spin Solid versus Magnetic Charge Ordered State in Artificial Honeycomb Lattice of Connected Elements

The nature of magnetic correlation at low temperature in two-dimensional artificial magnetic honeycomb lattice is a strongly debated issue. While theoretical researches suggest that the system will develop a novel zero entropy spin solid state as T --> 0 K, a confirmation to this effect in artificial honeycomb lattice of connected elements is lacking. We report on the investigation of magnetic correlation in newly designed artificial permalloy honeycomb lattice of ultra-small elements, with a typical length of ~ 12 nm, using neutron scattering measurements and temperature dependent micromagnetic simulations. Numerical modeling of the polarized neutron reflectometry data elucidates the temperature dependent evolution of spin correlation in this system. As temperature reduces to ~ 7 K, the system tends to develop novel spin solid state, manifested by the alternating distribution of magnetic vortex loops of opposite chiralities. Experimental results are complemented by temperature dependent micromagnetic simulations that confirm the dominance of spin solid state over local magnetic charge ordered state in the artificial honeycomb lattice with connected elements. Our results enable a direct investigation of novel spin solid correlation in the connected honeycomb geometry of two-dimensional artificial structure.

cond-mat.mes-hall↗

arXiv2016

Electrically driven magnetic antenna based on multiferroic composites

We suggest and demonstrate via large scale numerical simulations an electrically operated spin- wave inducer based on composite multiferroic junctions. Specifcally, we consider an interfacially coupled ferromagnetic/ferroelectric structure that emits controllably spin waves in the ferromagnets if the ferroelectric polarization is poled by an external electric field. The roles of geometry and material properties are discussed.

cond-mat.mes-hall↗

arXiv2016

Kinetics of nano-size Ferroelectrics

We analyze theoretically the finite-temperature polarization dynamic in displacive-type ferroelectrics. In particular we consider the thermally-activated switching time of a single-domain ferroelectric polarization studied by means of the Landau-Khalatnikov equation, extended as to capture thermal fluctuations. The results are compared with the switching time formula that follows from the analytical solution of Pauli master equations. In a second step we focus on the phase diagram of a prototypical ferroelectric as described by the temperature-dependent Landau-Devonshire model including thermal fluctuations. Our simulations show the emergence of phase instability at reduced sizes which we attribute to thermal fluctuations in the order parameter in the respective phase. We conclude that, along with the temperature-dependent potential coefficients, thermal fluctuations should be taken into account to achieve a comprehensive description of the thermal behavior of reduced-size ferroelectrics. To endorse our conclusions, we simulated the electric-field activated switching time for a multi-domain system and compared the results to the predictions of well-established models such as the Kolmogorov-Avrami-Ishibashi.

cond-mat.mtrl-sci↗

arXiv2016

Thermally induced magnonic spin current, thermomagnonic torques and domain wall dynamics in the presence of Dzyaloshinskii-Moriya interaction

Thermally activated domain wall (DW) motion in magnetic insulators has been considered theoretically, with a particular focus on the role of Dzyaloshinskii-Moriya Interaction (DMI) and thermomagnonic torques. The thermally assisted DW motion is a consequence of the magnonic spin current due to the applied thermal bias. In addition to the exchange magnonic spin current and the exchange adiabatic and the entropic spin transfer torques, we also consider the DMI-induced magnonic spin current, thermomagnonic DMI field-like torque and the DMI entropic torque. Analytical estimations are supported by numerical calculations. We found that the DMI has a substantial influence on the size and the geometry of DWs, and that the DWs become oriented parallel to the long axis of the nanostrip. Increasing the temperature smoothes the DWs. Moreover, the thermallyinduced magnonic current generates a torque on the DWs, which is responsible for their motion. From our analysis it follows that for a large enough DMI the influence of DMI-induced field-like torque is much stronger than that of the DMI and the exchange entropic torques. By manipulating the strength of the DMI constant, one can control the speed of the DW motion, and the direction of the DW motion can be switched, as well. We also found that DMI not only contributes to the total magnonic current, but also it modifies the exchange magnonic spin current, and this modification depends on the orientation of the steady state magnetization. The observed phenomenon can be utilized in spin caloritronics devices, for example in the DMI based thermal diodes. By switching the magnetization direction, one can rectify the total magnonic spin current.

cond-mat.mes-hall↗

arXiv2014

Dipole-dipole interaction in arrays of Fe/Fe$_x$O$_y$ core/shell nanocubes probed by ferromagnetic resonance

This paper represents a detailed theoretical study of the role of the longrange magnetic dipole-dipole interaction evidenced by the ferromagnetic resonance (FMR) spectra for the ordered arrays of cubic nanoparticles. We show that the size of the array essentially controls the stability of the system, allowing to suppress the intermittent low-field excitations starting from the arrays formed by 6x6 nanoparticles. Our numerical simulations allow to determine the threshold inter-particle distance (around 80 ÷ 100 nm), after which the dipole-dipole interaction becomes negligible so that the FMR spectrum of the nanoparticle arrays becomes the same as the spectrum featured by a single nanoparticle. We also compare our simulations with experimental FMR-spectra of 24 Fe/Fe$_x$O$_y$-nanocubes irregularly placed on a substrate.

cond-mat.mtrl-sci↗

arXiv2014

Coercivity reduction in a two-dimensional array of nanoparticles

We report on theoretical investigation of the magnetization reversal in two-dimensional arrays of ferromagnetic nano-particles with parameters of cobalt. The system was optimized for achieving the lowest coercivity in an array of particles located in the nodes of triangular, hexagonal and square grids. Based on the numerical solution of the non-stochastic Landau-Lifshitz-Gilbert equation we show that each particle distribution type is characterized with a proper optimal distance, allowing to lower the coercivity values for approximately 30% compared with the reference value obtained for a single nano-particle. It was shown that the reduction of coercivity occurs even if the particle position in the array is not very precise. In particular, the triangular particle arrangement maintained the same optimal distance between the particles under up to 20% random displacements of their position within the array.

cond-mat.mtrl-sci↗

arXiv2014

On the longitudinal spin current induced by a temperature gradient in a ferromagnetic insulator

Based on the solution of the stochastic Landau-Lifshitz-Gilbert equation discretized for a ferromagnetic chain subject to a uniform temperature gradient, we present a detailed numerical study of the spin dynamics with a focus particularly on finite-size effects. We calculate and analyze the net longitudinal spin current for various temperature gradients, chain lengths, and external static magnetic fields. In addition, we model an interface formed by a nonuniformly magnetized finite-size ferromagnetic insulator and a normal metal and inspect the effects of enhanced Gilbert damping on the formation of the space-dependent spin current within the chain. A particular aim of this study is the inspection of the spin Seebeck effect beyond the linear response regime. We find that within our model the microscopic mechanism of the spin Seebeck current is the magnon accumulation effect quantified in terms of the exchange spin torque. According to our results, this effect drives the spin Seebeck current even in the absence of a deviation between the magnon and phonon temperature profiles. Our theoretical findings are in line with the recently observed experimental results by M. Agrawal et al., Phys. Rev. Lett. 111, 107204 (2013).

cond-mat.mtrl-sci↗

arXiv2014

Gromov's Non-Squeezing Theorem and Beltrami type equation

We introduce a method for constructing J-complex discs. The method only uses the standard scheme for solving the Beltrami equation and the Schauder principle. As an application, we give a short self-contained proof of Gromov's Non-Squeezing Theorem.

math.SG↗

arXiv2013

Thermally activated in-plane magnetization rotation induced by spin torque

We study the role of thermal fluctuations on the spin dynamics of a thin permalloy film with a focus on the behavior of spin torque and find that the thermally assisted spin torque results in new aspects of the magnetization dynamics. In particular, we uncover the formation of a finite, spin torque-induced, in-plane magnetization component. The orientation of the in-plane magnetization vector depends on the temperature and the spin-torque coupling. We investigate and illustrate that the variation of the temperature leads to a thermally-induced rotation of the in-plane magnetization.

cond-mat.mes-hall↗

arXiv2013

Beating the superparamagnetic size limit of nanoparticles on a ferroelectric substrate

When decreasing the size of nanoscale magnetic particles their magnetization becomes vulnerable to thermal fluctuations as approaching the superparamgnetic limit, hindering thus applications relying on a stable magnetization. Here, we show theoretically that a magnetoelectric coupling to a ferroelectric substrate renders possible the realization of substantially smaller nano clusters with thermally stable magnetization. For an estimate of cluster size we perform calculations with realistic material parameters for iron nano particles on ferroelectric BaTiO3 substrate. We find, steering the polarization of BaTiO3 with electric fields affects the magnetism of the deposited magnetic clusters. These findings point to a qualitatively new class of superparamagnetic composites.

cond-mat.mtrl-sci↗

arXiv2013

Dynamics of localized modes in a composite multiferroic chain

In a coupled ferroelectric/ferromagnetic system, i.e. a composite multiferroic, the propagation of magnetic or ferroelectric excitations across the whole structure is a key issue for applications. Of a special interest is the dynamics of localized magnetic or ferroelectric modes (LM) across the ferroelectric-ferromagnetic interface, particularly when the LM's carrier frequency is in the band of the ferroelectric and in the band gap of the ferromagnet. For a proper choice of the system's parameters, we find that there is a threshold amplitude above which the interface becomes transparent and a band gap ferroelectric LM penetrates the ferromagnetic array. Below that threshold, the LM is fully reflected. Slightly below this transmission threshold, the addition of noise may lead to energy transmission, provided that the noise level is not too low nor too high, an effect that resembles stochastic resonance. These findings represent an important step towards the application of ferroelectric and/or ferromagnetic LM-based logic.

cond-mat.mes-hall↗

arXiv2013

Entanglement between nitrogen vacancy spins in diamond controlled by a nanomechanical resonator

We suggest a new type of nano-electromechanical resonator, the functionality of which is based on a magnetic field induced deflection of an appropriate cantilever that oscillates between nitrogen vacancy (NV) spins in daimond. Specifically, we consider a Si(100) cantilever coated with a thin magnetic Ni film. Magnetoelastic stress and magnetic-field induced torque are utilized to induce a controlled cantilever deflection. It is shown that, depending on the value of the system parameters, the induced asymmetry of the cantilever deflection substantially modifies the characteristics of the system. In particular, the coupling strength between the NV spins and the degree of entanglement can be controlled through magnetoelastic stress and magnetic-field induced torque effects. Our theoretical proposal can be implemented experimentally with the potential of increasing several times the coupling strength between the NV spins as compared to the maximal coupling strength reported before in P. Rabl, et al. Phys. Rev. B 79, 041302(R) (2009).

quant-ph↗

arXiv2012

Magnetoelectric coupling in a ferroelectric/ferromagnetic chain revealed by ferromagnetic resonance

Understanding the multiferroic coupling is one of the key issues in the feld of multiferroics. As shown here theoretically, the ferromagnetic resonance (FMR) renders possible an access to the magnetoelectric coupling coefficient in composite multiferroics. This we evidence by a detailed analysis and numerical calculations of FMR in an unstrained chain of BaTiO3 in the tetragonal phase in contact with Fe, including the effect of depolarizing field. The spectra of the absorbed power in FMR are found to be sensitive to the orientation of the interface electric polarization and to an applied static electric field. Here we propose a method for measuring the magnetoelectric coupling coefficient by means of FMR.

cond-mat.mtrl-sci↗

arXiv2012

Theoretical proposal for the dynamical control of the nonlinear optical response frequency

We propose theoretically a method for the control of the frequency of the nonlinear optical response of a model nonlinear medium driven by an electric field and suggest an experimental realization on the basis of isotropic LiF, or NaCl crystals and pulsed Nd glass laser. The theoretical background of the proposed optical control is the nonlinear resonance and the resonance overlapping which is typical for nonlinear systems. It is shown that by a proper choice of the parameters of the applied pulses a diffusive growth of the oscillation amplitude can be achieved resulting in a controlled switching of the system's frequency. The maximum frequency of the nonlinear response is identified to be proportional to the intensity of the applied noise. An experimental suggestion for particular materials is proposed.

physics.optics↗

arXiv2012

Levi-flat filling of real two-spheres in symplectic manifolds (II)

We consider a compact complex manifold with smooth Levi convex boundary and a tame symplectic form. Consider a real two-sphere with elliptic and hyperbolic complex points generically embedded to the boundary of manifold. We prove a result on filling of the sphere by a Levi-flat hypersurface.

math.CV↗