Факультет електроніки та інформаційних технологій (ЕлІТ)
Permanent URI for this communityhttps://devessuir.sumdu.edu.ua/handle/123456789/20
Browse
25 results
Search Results
Item Directed transport of suspended ferromagnetic nanoparticles under both gradient and uniform magnetic fields(IOP Publishing, 2020) Денисов, Станіслав Іванович; Денисов, Станислав Иванович; Denysov, Stanislav Ivanovych; Лютий, Тарас Володимирович; Лютый, Тарас Владимирович; Liutyi, Taras Volodymyrovych; Павлюк, Максим Олександрович; Павлюк, Максим Александрович; Pavliuk, Maksym OleksandrovychThe suspended ferromagnetic particles subjected to the gradient and uniform magnetic fields experience both the translational force generated by the field gradient and the rotational torque generated by the fields strengths. Although the uniform field does not contribute to the force, it nevertheless influences the translational motion of these particles. This occurs because the translational force depends on the direction of the particle magnetization, which in turn depends on the fields strengths. To study this influence, a minimal set of equations describing the coupled translational and rotational motions of nanosized ferromagnetic particles is introduced and solved in the low Reynolds number approximation. Trajectory analysis reveals that, depending on the initial positions of nanoparticles, there exist four regimes of their directed transport. The intervals of initial positions that correspond to different dynamical regimes are determined, their dependence on the uniform magnetic field is established, and strong impact of this field on the directed transport is demonstrated. The ability and efficiency of the uniform magnetic field to control the separation of suspended ferromagnetic nanoparticles is also discussed.Item Induced magnetization and power loss for a periodically driven system of ferromagnetic nanoparticles with randomly oriented easy axes(American Physical Society, 2016) Denysov, Stanislav Ivanovych; Денисов, Станислав Иванович; Денисов, Станіслав Іванович; Лютий, Тарас Володимирович; Лютый, Тарас Владимирович; Lyutyy, Taras Volodymyrovych; Педченко, Богдан Олександрович; Педченко, Богдан Александрович; Pedchenko, Bohdan Oleksandrovych; Гришко, Олександр Миколайович; Гришко, Александр Николаевич; Hryshko, Oleksandr MykolaiovychWe study the effect of an elliptically polarized magnetic field on a system of non-interacting, single-domain ferromagnetic nanoparticles characterized by a uniform distribution of easy axis directions. Our main goal is to determine the average magnetization of this system and the power loss in it. In order to calculate these quantities analytically, we develop a general perturbation theory for the Landau-Lifshitz-Gilbert (LLG) equation and find its steady-state solution for small magnetic field amplitudes. On this basis, we derive the second-order expressions for the average magnetization and power loss, investigate their dependence on the magnetic field frequency, and analyze the role of subharmonic resonances resulting from the nonlinear nature of the LLG equation. For arbitrary amplitudes, the frequency dependence of these quantities is obtained from the numerical solution of this equation. The impact of transitions between different regimes of regular and chaotic dynamics of magnetization, which can be induced in nanoparticles by changing the magnetic field frequency, is examined in detail.Item Temperature Dependence of the Drift Velocity of Ferromagnetic Nanoparticles in Viscous Fluids(Sumy State University, 2018) Денисов, Станіслав Іванович; Денисов, Станислав Иванович; Denysov, Stanislav Ivanovych; Yermolenko, A.S.; Bosenko, V.S.In Refs. [1, 2], the deterministic theory of drift of single-domain ferromagnetic nanoparticles in viscous fluids, which occurs due to the Magnus effect, has recently been developed and numerically confirmed. Here, we present analytical and numerical results obtained within the stochastic theory on the influence of temperature on the drift velocity.Item Minimal Set of Equations for Drift of Ferromagnetic Nanoparticles Induced by Magnetic Fields in Fluids(Sumy State University, 2018) Денисов, Станіслав Іванович; Денисов, Станислав Иванович; Denysov, Stanislav Ivanovych; Лютий, Тарас Володимирович; Лютый, Тарас Владимирович; Liutyi, Taras Volodymyrovych; Kvasnina, O.V.; Yermolenko, A.S.Recently, it has been established that ferromagnetic nanoparticles subjected to a periodic force and a non-uniformly rotating magnetic field can drift in a viscous fluid due to the Magnus effect. Because the drift phenomenon is of interest for applications such as particle separation, in this work we present a minimal set of equations for describing this phenomenon when a periodic force is induced by a gradient magnetic field.Item Energy Spectrum of a Particle in an Infinitely Deep Potential Well with a Non-flat Bottom(Sumy State University, 2018) Денисов, Станіслав Іванович; Денисов, Станислав Иванович; Denysov, Stanislav Ivanovych; Husachenko, A.V.; Ryzhkov, O.S.To model the quantum behavior of current carriers in heterogeneous nanostructures, different potential wells and barriers are widely used. Of particular interest are those (including artificial ones) for which the corresponding Schrödinger equation can be solved exactly. One of them is an infinitely deep potential well with a flat bottom defined as 𝑈(𝑥) = ∞ for |𝑥| ≥ 𝑎 and 𝑈(𝑥) = 0 for |𝑥| < 𝑎. Here, we report on exact solution of the stationary Schrödinger equation in the case, when the potential bottom is non-flat, i.e., 𝑈(𝑥) = −𝑓𝑥 (𝑓 > 0) if |𝑥| < 𝑎. Physically, this means that the particle in the well is subjected to an external force 𝑓 in the 𝑥-direction.Item Influence of Spin-polarized Current on Spin Waves in Ferromagnets(Sumy State University, 2018) Денисов, Станіслав Іванович; Денисов, Станислав Иванович; Denysov, Stanislav Ivanovych; Shchotkin, V.V.It has been recently established that spin-polarized current can have a direct influence on the magnetization dynamics in conducting ferromagnets. This effect has quantum origin and is of great interest from both fundamental and applied viewpoints. In particular, it can be useful for developing magnetoresistance random access memory, magnetic logic elements and microwave devices, to name a few.Item Master Equation for a Localized Particle Driven by Poisson White Noise(Sumy State University, 2018) Денисов, Станіслав Іванович; Денисов, Станислав Иванович; Denysov, Stanislav Ivanovych; Bohopolskyi, V.M.; Shypilov, N.E.Fluctuations in nanosystems play an important role in forming their electric, magnetic, thermal and other properties. Usually, due to the central limit theorem of probability theory, these fluctuations obey Gaussian statistics. However, in some cases, e.g., when the system is subjected to Poisson white noise, that is a random sequence of 𝛿-pulses, the system fluctuations are not Gaussian. Here, we derive the corresponding equation for the probability density function 𝑃(𝑥, 𝑡) of the system parameter 𝑥(𝑡) interpreted as a particle coordinate within an impenetrable box.Item New laws of anomalous superslow diffision(Sumy State University, 2013) Бистрик, Юрій Сергійович; Быстрик, Юрий Сергеевич; Bystryk, Yurii Serhiiovych; Денисов, Станіслав Іванович; Денисов, Станислав Иванович; Denysov, Stanislav IvanovychIn the present work we concern ourselves with the question of the existence of other anomalous diffusion laws generated by CTRWs. Based on our recent results on the asymptotic behavior of CTRWs with superheavytailed waiting time and asymmetric heavy-tailed jump length distributions (whose first and/or second moments are infinite), we find the conditions of superslow diffusion and establish corresponding laws by analytical methods and provide a verification using numerical simulation.Item Rotational properties of ferromagnetic nanoparticles driven by a precessing magnetic field in a viscous fluid(American Physical Society, 2015) Лютий, Тарас Володимирович; Лютый, Тарас Владимирович; Liutyi, Taras Volodymyrovych; Денисов, Станіслав Іванович; Денисов, Станислав Иванович; Denysov, Stanislav Ivanovych; Рева, Владіслав Валерійович; Рева, Владислав Валерьевич; Reva, Vladyslav Valeriiovych; Бистрик, Юрій Сергійович; Быстрик, Юрий Сергеевич; Bystryk, Yurii SerhiiovychWe study the deterministic and stochastic rotational dynamics of ferromagnetic nanoparticles in a precessing magnetic field. Our approach is based on the system of effective Langevin equations and on the corresponding Fokker-Planck equation. Two key characteristics of the rotational dynamics, namely the average angular frequency of precession of nanoparticles and their average magnetization, are of interest. Using the Langevin and Fokker-Planck equations, we calculate both analytically and numerically these characteristics in the deterministic and stochastic cases, determine their dependence on the model parameters, and analyze in detail the role of thermal fluctuations.Item Energy dissipation in single-domain ferromagnetic nanoparticles: Dynamical approach(American Physical Society, 2015) Лютий, Тарас Володимирович; Лютый, Тарас Владимирович; Liutyi, Taras Volodymyrovych; Денисов, Станіслав Іванович; Денисов, Станислав Иванович; Denysov, Stanislav Ivanovych; Peletskyi, A.Yu.; Binns, C.We study, both analytically and numerically, the phenomenon of energy dissipation in single-domain ferromagnetic nanoparticles driven by an alternating magnetic field. Our interest is focused on the power loss resulting from the Landau-Lifshitz-Gilbert equation, which describes the precessional motion of the nanoparticle magnetic moment. We determine the power loss as a function of the field amplitude and frequency and analyze its dependence on different regimes of forced precession induced by circularly and linearly polarized magnetic fields. The conditions to maximize the nanoparticle heating are also analyzed.
- «
- 1 (current)
- 2
- 3
- »