A mathematical model that describes the process of the reversal magnetization of an amorphous microwire with the help of a large Barkhausen jump is proposed. The model has been estimated with regard to the optimization of the signal-tonoise ratio. Using nonlinear model, we studied the physical factors that cause the fluctuations of the start field. Based on the results of numerical experiments, the new data on the behavior of the start field under different conditions of a switching in a bistable ferromagnetic, including the conditions of high-frequency swapping, have been obtained and compared to the existing data. The results obtained do not contradict the existing physical concepts concerning a domain wall motion and are more general and realistic in a comparison with the previous model.
In this paper the simulation of nonlinear electron dynamics in the metal-carbon tetramer nanocluster was carried out using the modified approach in a framework of jellium model. The model Hamiltonian includes the terms accounting the action of external electric field and the interaction between the tunneling electron with the vibrational modes of carbon shell. As a result, the system of differential equations for the amplitudes of the electron localization probability at the MCN centers was obtained and then at the various sets of model parameters it was solved numerically. The different regimes in the electron localization dynamics were revealed and the control role of the electric field was shown.
In the present work, the cast glass-coated amorphous microwires manufactured by the Ulitovsky-Taylor method are studied. Interest in the cast glass-coated amorphous microwires has greatly increased in the last few years mainly due to their technological applications, in particular, as the sensor elements in the various devices. Technological aspects of the Ulitovsky-Taylor method for the preparation of the glass-coated microwires with the different radius are analyzed. It is essential that the microwires are manufactured using a rapid solidification technique. The geometrical characteristics of a microwire depend on the physical properties of a metal and of glass, the diameter of the initial glass tube, and the parameters of the heating inductor. The given method provides the microwire geometric parameters of within the wide ranges. Respectively, a metallic core diameter in these microwires can range from 0.5 to 70 μm, and their glass-coating thickness can be varied from 1 to 50 μm. Moreover, the length of the derivable samples can reach up to 104 m. The obtained microwires exhibit the magnetic properties, which are high dependent on the metallic core composition, and similarly as it was done here for the residual stresses, they can be expressed through the microwire geometric parameters.
In this paper it is offered the simplest microscopic model for the description of the nanocomposite material, which is found under action of external electromagnetic (electric) field. At that, the trimer nanocluster embedded in the weakly structured non-dissipative matrix (for example, the polymeric, organic or amorphous types) is modeled as three- center molecular complex with one "excess" tunneling electron and all its centers are considered together with account of theirs ligand environment. The proposed model description is suitable to the trimer nanoclusters of bridge type, and to the nanotrimers such type in which the ions of 3d-metals and theirs oxides have the various oxidation degrees, and also to other three-center molecular complexes of similar types. For posed problem a description of external and internal factors and analysis of their interconnections are performed. Herewith, the given model is also characterized by fact that in addition to the explicit connections of its basic factors they, furthermore, are implicitly interconnected. Then, the mathematical model is formulated so that to contain an optimal number of model parameters for a detailed description of considered factors and its interconnections. In the result of numerical simulation can to identify the electron localization regimes in the trimer nanocluster and the values of controlling model parameters responsible for switching between the obtained regimes.
In the framework of the stochastic approach to the description of the interaction between the quantum dimer nanocluster
with two electrons and dissipative environment, such as a weak structured organic matrix, the electron transfer kinetics is
theoretically investigated. The minimal theoretical model formulated here involves the applying of Redfield’s theory for
the reduced density matrix and the using of Haken-Strobl approximation. The dimer nanocluster is considered in the
model “two centers – two electrons”, which is described with using of Hubbard’s Hamiltonian, so that the electron
correlation is taken into account. It was found that the difference in the electron populations on the dimer nanocluster
centers has an oscillatory time dependence with a beats, which is damping due to the influence of a weak structured
matrix as a thermostat. This manifests itself as a change in the nanodimer dipole moment, i.e. during of the relaxation
time determined by a dissipative environment holds the switching of nanodimer between the states with the opposite
directions of its dipole moment. Eventually, the dimer nanocluster relaxes from an initial state with two electrons on one
center to the final state with a uniform distribution of electrons on the centers. It is shown how the switching is modified
for the different values of the nanodimer parameters and dissipation parameter. This switching regime in the nanosystem
studied here is interesting for various device applications due to the ability to control the state of such nanosystem
by action of the external electric and magnetic fields.
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