Факультет електроніки та інформаційних технологій (ЕлІТ)
Permanent URI for this communityhttps://devessuir.sumdu.edu.ua/handle/123456789/20
Browse
75 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 Microwave absorption by a rigid dipole in a viscous fluid(IEEE, 2016) Лютий, Тарас Володимирович; Лютый, Тарас Владимирович; Lyutyy, Taras Volodymyrovych; Рева, Владислав Валерійович; Рева, Владислав Валериевич; Reva, Vladyslav ValeriiovychWe present a comprehensive theoretical and numerical study of the stochastic rotational motion of a high anisotropic ferromagnetic nanoparticle in a viscous carrier driven by a time-periodic field. The effects of energy absorption of circularly and linearly polarized fields are analyzed. The analytical expressions and numerical data for the probability density and the power loss are compared for different values of the system parameters. Their coincidence and divergence are discussed.Item Energy dissipation of interacting rigid dipoles driven by the RF-field in a viscous fluid(IEEE, 2017) Лютий, Тарас Володимирович; Лютый, Тарас Владимирович; Lyutyy, Taras Volodymyrovych; Рева, Владислав Валерійович; Рева, Владислав Валериевич; Reva, Vladyslav Valeriiovych; Єрмоленко, Андрій Сергійович; Ермоленко, Андрей Сергеевич; Yermolenko, Andrii SergiyovychWe have considered the response of an ensemble of uniaxial ferromagnetic nanoparticles placed into a fluid to an alternating field in the presence of thermal bath. The attention was paid to the absorption of the field energy as a result of nanoparticles rotation in a viscous fluid. The influence of the inter-particle interaction effects was studied numerically based on the effective Langevin equation. Using the Barnes-Hut algorithm and CUDA technology, the set of numerical results, which describes the frequency dependence of the power loss, has obtained for various system parameters.Item Forced coupled motion of the nanoparticle magnetic moment and the whole nanoparticle in a viscous fluid(IEEE, 2017) Лютий, Тарас Володимирович; Лютый, Тарас Владимирович; Lyutyy, Taras Volodymyrovych; Денисова, Олена Станіславівна; Денисова, Елена Станиславовна; Denisova, Elena Stanislavivna; Kvasnina, A.V.We considered the coupled motion of the magnetic moment of a ferromagnetic uniaxial nanoparticle and its mechanical rotation about the center of mass. This particle is supposed to be placed into a viscous liquid and excited by an external alternating magnetic field. Two modes of motion were studied analytically in the noise-free approximation. Within the first mode, both the nanoparticle magnetic moment and easy axis perform small oscillations around the initial position. The oscillation amplitudes were obtained in the harmonic approximation. Just the magnetic moment demonstrates the resonant behaviour that causes the main features of the oscillation mode. Within the second mode, the nanoparticle magnetic moment and easy axis are rotated synchronously. In this case we obtained the system of algebraic equations, where the precession and lag angles of the magnetic moment and easy axis are the solutions of these equations. The results obtained allow to make an analysis of the mechanism of ferrofluids heating by alternating magnetic fields.Item Power loss for a periodically driven ferromagnetic nanoparticle in a viscous fluid: The finite anisotropy aspects(Elsevier, 2018) Лютий, Тарас Володимирович; Лютый, Тарас Владимирович; Lyutyy, Taras Volodymyrovych; Гришко, Олександр Миколайович; Гришко, Александр Николаевич; Hryshko, Oleksandr Mykolaiovych; Ковнер, А.А.The joint magnetic and mechanical motion of a ferromagnetic nanoparticle in a viscous fluid is considered within the dynamical approach. The equation based on the total momentum conservation law is used for the description of the mechanical rotation, while the modified Landau-Lifshitz-Gilbert equation is utilized for the description of the internal magnetic dynamics. The exact expressions for the particles trajectories and the power loss are obtained in the linear approximation. The comparison with the results of other widespread approaches, such as the model of fixed particle and the model of frozen magnetic moment, is performed. It is established that in the small oscillations mode the damping precession of the nanopartile magnetic moment is the main channel of energy dissipation, but the motion of the nanoparticle easy axis can significantly influence the value of the resulting power loss.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 Energy dissipation of rigid dipoles in a viscous fluid under the action of a time-periodic field: The influence of thermal bath and dipole interaction(American Physical Society, 2018) Лютий, Тарас Володимирович; Лютый, Тарас Владимирович; Lyutyy, Taras Volodymyrovych; Рева, Владислав Валерійович; Рева, Владислав Валериевич; Reva, Vladyslav ValeriiovychFerrofluid heating by an external alternating field is studied based on the rigid dipole model, where the magnetization of each particle in a fluid is supposed to be firmly fixed in the crystal lattice. Equations of motion, employing Newton's second law for rotational motion, the condition of rigid body rotation, and the assumption that the friction torque is proportional to angular velocity are used. This oversimplification permits us to expand the model easily: to take into account the thermal noise and interparticle interaction that allows us to estimate from unified positions the role of thermal activation and dipole interaction in the heating process. Our studies are conducted in three stages. The exact expressions for the average power loss of a single particle are obtained within the dynamical approximation. Then, in the stochastic case, the power loss of a single particle is estimated analytically using the Fokker-Planck equation and numerically using the effective Langevin equation. Finally, the power loss for the particle ensemble is obtained using the molecular dynamics method. Here, the local dipole fields are calculated approximately based on the Barnes-Hut algorithm. The revealed trends in the behavior of both a single particle and the particle ensemble suggest the way of choosing the conditions for obtaining the maximum heating efficiency. The competitiveness character of the interparticle interaction and thermal noise is investigated in detail. Two situations, when the thermal noise rectifies the power loss reduction caused by the interaction, are described. The first of them is related to the complete destruction of dense clusters at high noise intensity. The second one originates from the rare switching of the particles in clusters due to thermal activation, when the noise intensity is relatively weak. In this way, the constructive role of noise appears in the system.Item Uniform and nonuniform precession of a nanoparticle with finite anisotropy in a liquid: Opportunities and limitations for magnetic fluid hyperthermia(Elsevier, 2019) Лютий, Тарас Володимирович; Лютый, Тарас Владимирович; Liutyi, Taras Volodymyrovych; Гришко, Олександр Миколайович; Гришко, Александр Николаевич; Hryshko, Oleksandr Mykolaiovych; Yakovenko, M.Yu.We focus on an in-depth study of the forced dynamics of a ferromagnetic single-domain uniaxial nanoparticle placed in a viscous fluid and driven by an external rotating magnetic field. The process of conversion of magnetic and mechanical energies into heat is a physical basis for magnetic fluid hyperthermia that is very promising for cancer treatment. The dynamical approximation allows us to establish the limits of the heating rate and understand the logic of selection of the system parameters to optimize the therapy. Based on the developed analytical and numerical tools, we analyze from a single viewpoint the synchronous and asynchronous rotation of the nanoparticle or/and its magnetization in the following three cases. For the beginning, we actualize the features of the internal magnetic dynamics, when the nanoparticle body is supposed to be fixed. Then, we study the rotation of the whole nanoparticle, when its magnetization is supposed to be locked to the crystal lattice. And, finally, we realize the analysis of the coupled motion, when the internal magnetic dynamics is performed in the rotated nanoparticle body. In all these cases, we describe analytically the uniform mode, or synchronous rotation along with an external field, while the nonuniform mode, or asynchronous rotation, is investigated numerically.Item Temperature effects on drift of suspended single-domain particles induced by the Magnus force(American Physical Society, 2018) Денисов, Станіслав Іванович; Денисов, Станислав Иванович; Denisov, Stanislav Ivanovych; Лютий, Тарас Володимирович; Лютый, Тарас Владимирович; Lyutyy, Taras Volodymyrovych; Рева, Владислав Валерійович; Рева, Владислав Валериевич; Reva, Vladyslav Valeriiovych; Єрмоленко, Андрій Сергійович; Ермоленко, Андрей Сергеевич; Yermolenko, Andrii SeriyovychWe study the temperature dependence of the drift velocity of single-domain ferromagnetic particles induced by the Magnus force in a dilute suspension. A set of stochastic equations describing the translational and rotational dynamics of particles is derived, and the particle drift velocity that depends on components of the average particle magnetization is introduced. The Fokker-Planck equation for the probability density of magnetization orientations is solved analytically in the limit of strong thermal fluctuations for both the planar rotor and general models. Using these solutions, we calculate the drift velocity and show that the out-of-plane fluctuations of magnetization, which are not accounted for in the planar rotor model, play an important role. In the general case of arbitrary fluctuations, we investigate the temperature dependence of the drift velocity by numerically simulating a set of effective stochastic differential equations for the magnetization dynamics.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.